No cat

Hi BOB Naylor, hi guys. Ijust remove my cat and put pipe. And my shifting and power little bit improved, but not everything. I know i am piss you off with bunch of questions, but we really cant find problem. And problem is missfire. I have two questions: 1st After long of driving my fuel pump little bit noise, i can try to open and clean it but i dont know if it can cause it. 2nd Can cause this 1st oxygen sensor with no codes. And last one, how i can check my injectors for continuity, connector near the alternator is have a lot of legs. I thought it suposed to be 12 but looks like more, Alldata dont have this info. And maybe you can came up with more ideas, what can cause missfire. Steve 3.4, 86000, fuel and air filter, plugs and wires, MAF,PCV.
Thank you so much.

Do you feel a noticeable misfire and if so under what conditions? Any codes for a misfire also?

No codes. Engine shaking on just ideling.

I've got to give you credit you are persistent and not ready to give up but that is good.

Are you 100% sure you do not have a vacuum leak? Check all vacuum line connections in and around the intake manifold. A loose or cracked vacuum line will make the engine shake and have a poor idle with no misfire DTC error codes or SES light. Did you ever test your engine vacuum?

To ohm out the fuel injectors you can do it at that connector plug unless you prefer removing the upper intake manifold to access the fuel injectors but you'll need the color coding and pinouts from the service manual for your year Impala. Fuel injector coil resistance should be around 11.4 and 12.6 ohms.

Let us know yor findings. Good luck!

On my 3.8L engine there is an IAC valve (idel air control valve) mounted on the throttle body next to the MAF sensor... I pulled the IAC valve and it was all carboned up... I did a real good cleaning job on it and noticed an improvement in idle smoothness...

Not sure if the 3.4L is set up the same way...

I just check vacuum 17-18in. On top post i tolld you about fuel pump, that i have wining after long trips, can i clean it some how or maybe something wrong with it.(cause like i asume we have filter only after pump not before) But pressure i have 52-53 psi. And another question what symptoms malfunction oxygen sensor(1ST), and does it gonna trow a code?
And i did some reserches and find that harmonic balancer can do missfire too. Does anyone had this problem(balancer) on 2003 with 86000m.
About colors on connector(injectors), where i can find them, alldat dont have that# C102(16 cavities). And i dont have manual.
Thank you for info/

Somebody have info about IAC. Cant find it. I open mine looks real bad, maybe that causing my problem. I need model number, and where i can get it.

Somebody have info about IAC. Cant find it. I open mine looks real bad, maybe that causing my problem. I need model number, and where i can get it.

They always look bad. It accumulates a lot of soft carbon. Just clean it first. Use carb or throttle body cleaner on the spring loaded pintle. Then clean the seat where the IAC mounts to the throttle body. There is an air passage/orifice on the TB side that can clog up with the soft carbon. Clean the inside of the throttle body. Try that first and if it doesn't help let us know and we'll go from there.

Hello guys. I have two good news. 1st i paid my car off. 2nd after cleaning IAC, now llitle bit better, but still like missfire. I wanna buy new IAC cause when i start clean it spring and pin fall off. Then i notice the pin have a treads, i screw it back. After all job done i had problem to start the engine. I just wanna replace it, i dont wanna play around with that. I need model # and where i can get it. Satturday i try to check my compression, i got that gage. One question beside this. What functions of air intake temp. sensor. Probably i am gonna try to change bunch of sensors. About IAC, i never saw such a dirty parts. I have better power now but not at all, my shifting is anoing and think that because of missfire. If somebody have connector colors for injectors i would be apreciated.
Thank you for reply.

I wanna buy new IAC cause when i start clean it spring and pin fall off. Then i notice the pin have a treads, i screw it back. After all job done i had problem to start the engine. I just wanna replace it, i dont wanna play around with that. I need model # and where i can get it. Thank you for reply.


The IAC is GM part # 17112350, list $118.45 available at a GM Dealer.

AZ has Wells brand part # AC107 for around $40.00.

What is AZ?

What is AZ?

Autozone

The IAC is GM part # 17112350, list $118.45 available at a GM Dealer.

AZ has Wells brand part # AC107 for around $40.00.

That's a big price difference between the GM part and the AZ part!... I'd be concerned about the quality of the cheap AZ part...

That's a big price difference between the GM part and the AZ part!... I'd be concerned about the quality of the cheap AZ part...

I agree but the GM list price is inflated. GMPartsDirect.com has it for $61.59 but there will be a shipping charge and waiting time for the part. I used a Wells brand IAT sensor before and it worked. :dunno:

Sounds like YSteve needs one sooner since he messed up the IAC.

Guys like i tolld you before, i am gonna change bunch of sensors. So here you go: Yesterday i order(from GM) folowing: PURGE CONTROL VALVE, AIR INTAKE TEMP. SENSOR, PCV, IAC, MAP SENSOR. It was around 200$. This parts gonna be delivered on friday. Satturday iam gonna install all this and gonna respond. If this not gonna work will go farther. Then i have to change rest of sensors, and i am gonna need your help to figure out wich ones. You now i dont care about money right now, i just want this done. Whatever it gonna cost me. I am pissed alredy bacause no power and hard shifting.
What you think, this cant be mounts, right?(about hard shifting)
Can it be Oxygen sensor(1st)? (about no power)
Thank you BOB and GEMS.

What is the "Purge Control Valve"? And where is it?

Service and Repair
EVAPORATIVE EMISSION (EVAP) CANISTER PURGE VALVE REPLACEMENT

REMOVAL PROCEDURE



Disconnect the evaporative emission (EVAP) canister purge valve electrical connector.
Disconnect the EVAP canister purge pipe from the EVAP canister purge valve.
Disconnect the vacuum supply hose from the EVAP canister purge valve.

Remove the EVAP canister purge valve bolt.
Remove the EVAP canister purge valve from the intake manifold.INSTALLATION PROCEDURE



Position the EVAP canister purge valve to the intake manifold. NOTE: Refer to Fastener Notice in Service Precautions.
Install the EVAP canister purge valve bolt. Tighten Tighten the bolt to 10 N.m (89 lb in) .

Connect the vacuum supply hose to the EVAP canister purge valve.
Connect the EVAP canister purge pipe to the EVAP canister purge valve.
Connect the EVAP canister purge valve electrical connector.

ysteve... Why do the images you post keep changing?... The pictures in your reply seem to have no relation to the EVAP removal and replacement instructions... And each time I look the pictures you post change to something else... But don't worry about it... I'm not doing anything with that part... I was just curious why you mentioned it in one of your prior posts... I'm a Mechanical Engineer by profession but I've learned enough over the years to know one important rule: IF IT ISN'T BROKE, DON'T FIX IT!!!

What is the "Purge Control Valve"? And where is it?

On the 3800 it is the plastic cylinder looking part located in front of the right hand side (passenger) of the Upper Intake Manifold. Can't miss it. It has an electrical connector and vacuum lines. Part of the evaporative emissions system.

On the 3800 it is the plastic cylinder looking part located in front of the right hand side (passenger) of the Upper Intake Manifold. Can't miss it. It has an electrical connector and vacuum lines. Part of the evaporative emissions system.


OK, thanks... A word is worth a thousand pictures... :lol:

OK, thanks... A word is worth a thousand pictures... :lol:

Sometimes that is true Gems. But I had this in my collection just in case and decided to put it up since someone couldn't get the pics right. :lol:

http://i5.photobucket.com/albums/y186/lizzywiz/purge.jpg

Good clear photo... Can that EVAP valve get clogged and cause driveability problems?... I haven't heard of anyone changing that part out...

P.S. to ysteve: Your pics continue to change each time I look at this thread... Yet none of them show this EVAP valve that yau want to replace...

Good clear photo... Can that EVAP valve get clogged and cause driveability problems?... I haven't heard of anyone changing that part out...

P.S. to ysteve: Your pics continue to change each time I look at this thread... Yet none of them show this EVAP valve that yau want to replace...

Although I've helped people troubleshoot and fix a purge valve problem I've never had one go bad on any of the GM cars I have owned. The PCM will check the state of the purge valve and if it fails it should generate:

DTC P0441, EVAP Emission Control System Purge Flow Fault

The error code means that the valve is stuck either open or closed. Also, defective/cracked vacuum lines to and from it will trigger the same error code. When the P0441 sets it may cause the PCM to initiate a lean trim to the fuel injection system.

Yeah, our friend YSteve needs to do something about those pics. Some are causing the display to go into the scroll mode because the pixel size is too big.

About picture. I do not have a lot of posts. And administration of this site is not aproving to show it. I gonna just clear it.

About sensors. I am gonna buy all of them and just gonna use method of illumination.
I am going in front and think if those parts which gonna be delivered not gonna help. Look what i find. in the KS system are used by the PCM as microphones to listen for abnormal engine noise that may indicate pre-ignition/detonation.

About sensors. I am gonna buy all of them and just gonna use method of illumination.
I am going in front and think if those parts which gonna be delivered not gonna help. Look what i find. Looks like KNOCK sensor is important stuff and fragile. I think that can cause a problem too. Maybe some idiot on the car wash when changing oil filter with key broke it. But i look at it and seems to me fine maybe just gonna change it. What you think?
And what is that mean? I have 2 or 1 sensor on my 2003, 3.4?

What will you do if none of the sensors replaced shotgun fix your problem?

The knock sesnor is very important but should give a DTC error code if defective. Also, it is just the initial sensor. The KR sensing module for knock control is in the PCM module.

There should be 2 knock sensors on a 3.4L.

Hello guys. I am so pissed, stuff i order didnt help. I dont know what else it could be. I have a couple questions. Is cloged injector gonna trow a code, always or not? Can it be trotle position sensor or camshaft or oxygen? The thing is: maybe i have power wich should be, but i have missfire wich causing hard shifting, thats anoing. Please any advise apreciated. Special thanks for you Bob Naylor.

Another thing can it be vehicle speed sensor(hard shifting) or its gonna show me wrong on the instrument panel? Or maybe my tranny going down that what causing hard shifting?

ysteve: You have probably described this 100 times with "bnaylor" who is much more experienced than me with this car but let me ask you a few questions... You need to do more intelligent troubleshooting of your problem instead of randomly changing out parts hopeing it fixes your problem...

1. You say you have a misfire that is causing hard shifting... Are you sure you have a misfire?... Does it idle smooth?... Do you have any hesistation during acceleration?...

2. What is the condition of your spark plugs, ignition wires, ignition coil packs and the ignition control module?

3. Have you changed your fuel filter, PCV valve and air cleaner?

4. Have you cleaned the throttle body, MAF sensor and IAC valve?

5. Have you run any fuel injector cleaner through the car like LUCAS fuel injector cleaner or Sea Foam?

6. Have you changed the tranny fluid and tranny filter?

Please just answer these questions one at a time and maybe we can be more helpful to you...

Ok here you go.
1. Yes i have missfire, and hesistation on acceleration.
2. Before i put AC delco, now i have Bosch wires and plugs. Icheck continuity of coils and it looks normal. Inever heard of ignition control module( what the f**** is that)
3.Yes i changed ny PCV, air and fuel filter, Map sensor, Maf sensor,Intake air temp sensor, purge cont. valve,IAC sensor, all this brand new from AC Delco.
4.No i never cleand Throttle but i changed all folowing.
5.3 times i did thru the fuel tank and 1 time thru the intake vacuum line.
6. Yes i change my oil an filter in the tranny.

Ok here you go.
1. Yes i have missfire, and hesistation on acceleration.
2. Before i put AC delco, now i have Bosch wires and plugs. Icheck continuity of coils and it looks normal. Inever heard of ignition control module( what the f**** is that)
3.Yes i changed ny PCV, air and fuel filter, Map sensor, Maf sensor,Intake air temp sensor, purge cont. valve,IAC sensor, all this brand new from AC Delco.
4.No i never cleand Throttle but i changed all folowing.
5.3 times i did thru the fuel tank and 1 time thru the intake vacuum line.
6. Yes i change my oil an filter in the tranny.

OK, you sure have done lots of stuff...

The Ignition Control Unit Module is located directly under the 3 ignition coil paks... It's a flat rectangular part the 3 coil paks plug onto...The only reason I mention it is because my son used to be a Chevy mechanic and he's seen them go flaky on rare occassion, causing hard start and driveability issues (I thought I had this problem on my Impala)... It's not a cheap part... I believe the ACDelco price is about $190...

With all the work you have done why haven't you bought a can of throttle body cleaner and sprayed it clean?? It costs about $5... A dirty and gummed up throttle body is very often the source of problems like this...

I've heard of people having troubles with Bosch plugs and wires in the Impala's... They switched back to new OEM AC Delco plugs and wires...

First, how to clean throttle? I am not gonna damage anything?
Second Ac wires and plugs i had before and they was same like Bosch. I think new stuff everywhere same.

I agree with Gems. You need to put the original AC Delco spark plugs and ignition wires back in (new). The Bosch ign. wires are not as efficient as the AC Delco Packard or Premium Silicone 7mm wires. The AC Delco has the lowest resistance per foot. Bosch plugs leave a lot to be desired.

Next what exactly are your current symptoms. I lost track. How are you determining you have a misfire condition. Is the SES/CEL light on? Does it ever blink? Do you see any erratic idle at the tach? If you don' have a tach then put on an aftermarket one. Do you feel any engine vibration at idle? Through the steering? When looking at the engine do you see it shake?

How have you determined you are low on power? How is the acceleration? Can you spin the wheels at a dead stop?

Finally, explain the hard shifting you are getting? What are the conditions? Upshifts? Downshifts? Any specific rpm range? During hard acceleration or moderate, etc?

First, how to clean throttle? I am not gonna damage anything?
Second Ac wires and plugs i had before and they was same like Bosch. I think new stuff everywhere same.

Clean the throttle body using THROTTLE BODY SPRAY CLEANER... Buy a can of it at Autozone, Pep Boys, etc... Basically all you do is remove the flexible air intake tube and the grill that covers the throttle body intake... ALSO REMOVE THE MAF SENSOR BEFORE USING THE SPRAY CLEANER... It can be damaged by the cleaner... Spray the sufff in, stick a rag in and wipe, repeat the process... Open the throttle plate by hand and spray more... Keep doing this until you get it good and clean... The excess spray that runs out should become clear instead of brown when you have things clean... Reassemble everything and start your car... If it's like mine (I have the 3.8L) it will take a couple of cranks to start as the motor clears out the rest of the cleaner... That's it, easy job but very important...

BTW, you mentioned you changed the MAP sensor on your car (in addition to the MAF sensor)... Where is the MAP sensor located on the 3.8L engine?

He doesn't have to worry about the MAF sensor on a 3.4L. It is located on the intake duct way before the throttle body. Whereas on the 3800 it is located on the TB.

The MAP sensor on a 3800 is located above the PCV valve on the right hand side of the UIM. Can't miss it. One electrical connector will be visible.

The MAP sensor on a 3800 is located above the PCV valve on the right hand side of the UIM. Can't miss it. One electrical connector will be visible.

That's the part that needs to be removed (1/4 turn) to get to the PCV valve?

That's the part that needs to be removed (1/4 turn) to get to the PCV valve?

Part of it. You don't need to twist the forked retainer that goes over the PCV valve to remove the MAP sensor. Carefully press in on the two retainer forks pointing up to each side and pull up. And that is the MAP sensor.

I understand... Thanks... Now back to "ysteve" in this thread...

I understand... Thanks... Now back to "ysteve" in this thread...

I agree. Speaking of YSteve where is he?

I guess he must be taking the day off considering how long he has been working on this problem...what has it been over a month or more? :dunno:

No not month, alredy 6. Yes i feel on steering and saw like engine shaking. I dont have any SES exept that stupid P0420. Guys from JUSTANSWER saying hard shifting i have because of missfire. My shops around here is bunch of unskilld morons, cause they saying if no light then no problem. Shifting i have in all position low acceleration or high, just on high little bit smoother. Engine doesnt iddle smooth, even if you gonna put your hand where exhaust pipe you can feel gases is not streight. Yes i can spin the tires but not like i bought it 8 month ago. What else i should change? I have money so go ahead and tell couple more parts. One more thing i have valve ticking noise during acceleration. You think knock sensor under no sircumstanses gonna throw code if damaged? About spark plugs and wires(new) iam gonna change ASAP cause i have them in the trunk, they was before on the engine and no changes. On thing i noticed the little bit longer than my old ones DELPHI, i asked seller two time about maybe they from 3800 not for 3400, he sayid its for 3400. Continuity if fine. Thank you guys looks like only two of you helping me, i apreciate that. About day off, i dont have them, thats why i am responding only evening time. Sorry about alot of mistakes in the words cause iam only 3 year in the US.

No not month, alredy 6. Yes i feel on steering and saw like engine shaking. I dont have any SES exept that stupid P0420. Guys from JUSTANSWER saying hard shifting i have because of missfire. My shops around here is bunch of unskilld morons, cause they saying if no light then no problem. Shifting i have in all position low acceleration or high, just on high little bit smoother. Engine doesnt iddle smooth, even if you gonna put your hand where exhaust pipe you can feel gases is not streight. Yes i can spin the tires but not like i bought it 8 month ago. What else i should change? I have money so go ahead and tell couple more parts. One more thing i have valve ticking noise during acceleration. You think knock sensor under no sircumstanses gonna throw code if damaged? About spark plugs and wires(new) iam gonna change ASAP cause i have them in the trunk, they was before on the engine and no changes. On thing i noticed the little bit longer than my old ones DELPHI, i asked seller two time about maybe they from 3800 not for 3400, he sayid its for 3400. Continuity if fine. Thank you guys looks like only two of you helping me, i apreciate that. About day off, i dont have them, thats why i am responding only evening time. Sorry about alot of mistakes in the words cause iam only 3 year in the US.

So when does the hard shifting occur. What are the conditions? How bad does the shifting feel when it acts up?

On the valve ticking noise is that only under acceleration or does it sound more like detonation similar to when running poor quality gas.

All this stuff is happening on acceleration. And shifting is not so so hard its more like kick back shifting and its really annoing. Sorry i couldn respond yesterday, i was 100 miles form NY(bussines). So i cam back today and missfire is worse. So i still think i have shifting because of missfire. And another thing, i bought that commpression test gage and gonna run it in couple of days. Tommorow iam gonna try to clean my throtle. Tnanks for respond Bob.

Bob Look what i found. This sensors is left, rest of them i changed, remember, satturday. So i wanna put next order. Show wich of them i have to forget?
1.Camshaft pos. sensor

2.Crankshaft pos. sensor( there are two of then)

3.Knock sensor

4.Vehicle speed sensor

5.Thottle position sensor

6.Oxygen sensor (First-before cat)
And plus i find wire collors on injectors connector, after testing will respond.

Bob Look what i found. This sensors is left, rest of them i changed, remember, satturday. So i wanna put next order. Show wich of them i have to forget?
1.Camshaft pos. sensor

2.Crankshaft pos. sensor( there are two of then)

3.Knock sensor

4.Vehicle speed sensor

5.Thottle position sensor

6.Oxygen sensor (First-before cat)
And plus i find wire collors on injectors connector, after testing will respond.

Before wasting money on any more parts why don't you test the fuel injector coil resistance and do the engine compression test first.

Of the above sensors the throttle position sensor (TPS) if flaky could have an effect on the transmission.

If the vehicle speed sensor (VSS) was bad the shifting would be very erratic and the speedometer would probably read zero.

The two crank position sensors and the CAM position sensor are possibilities and may not give any error codes or SES light if flaky.

The front 02 sensor is a possibility if the misfire is when the PCM is in closed loop mode. Engine fully warmed up. When the engine is cold and while in open loop mode the 02 sensor is not used. Also, it is inhibited during acceleration.

On the knock sensor, if bad it should throw a code. Have you tried disconnecting the one by the oil filter and see what it does.

Thank you. Good info. I will respond evening.

Hi Bob. Look on my investigations: you was right about TPS, i disconnect it and my shifting time was long and throw me code P0122. About Knock sensor it was no changes just P0327. And plus i cleand my Throttle body(wasnt so dirty). Still no changes. About injector wires i couldnt able to check cause colors doesnt match. And compression too(can check only satturday dont have second person). I wanna ask you can those folowing sensors give the wrong readings, or they only working or if not working, giving you SES? And another thing do you ever heard about that, resonator or mufler geting cloged? I dont know what else to think. Thanks for your business.

Hi Bob. Look on my investigations: you was right about TPS, i disconnect it and my shifting time was long and throw me code P0122. About Knock sensor it was no changes just P0327. And plus i cleand my Throttle body(wasnt so dirty). Still no changes. About injector wires i couldnt able to check cause colors doesnt match. And compression too(can check only satturday dont have second person). I wanna ask you can those folowing sensors give the wrong readings, or they only working or if not working, giving you SES? And another thing do you ever heard about that, resonator or mufler geting cloged? I dont know what else to think. Thanks for your business.

I didn't say anything about disconnecting the TPS only the knock sensor but thats OK. At least your Powertrain Control Module (PCM) is not brain dead and is detecting faults although induced.

On the TPS the best way to check its operation is with a digital multimeter. At idle you will see around .4 volts on the output pin feeding back to the PCM. WOT will show around 4.0 volts. In between the voltage should be progressive and linear as you take the accelerator up. The reference voltage is around 5 volts from the PCM on the TPS connector.

On the wiring color coding that is a major problem no matter what documentation you use. Even the GM service manuals don't match what is actually installed. That is why most people simply remove the upper intake manifold to test the fuel injectors on a 3.4L. But if you are going to do that you might as well replace them and the o-ring seals. I would not rule out a flaky fuel injector(s).

I doubt the resonator is clogged but see how much pressure you are getting at the tailpipes. The last time I checked on a 3.4L GM car you can feel the exhaust pressure quite well. Try different rpms and rev it up while testing.

It would be nice to see the engine compression test results. Good luck!

Hi Bob. Today was changed TPS and no changes. One more thing i noticed, when my car is cold i can leave in yhe back BMW from stand still, but soon as it gets warm i start having missfire and loss of power and that anoing shifting. Sure you gonna ask me maybe you have tranny slipage, iam saying no. But i saw somewhere that pipes feed and return(tranny cooler) geting cloged and tranny frying. But i saw it ones and cant find it. Do you heard about that people had some simmilar problems. Compression test comming soon, maybe this wekend. Maybe anything else you can add or tell me to try anything. And can it be that fuel pressure regulator geting restricted when hot? Allright, any info apreciated.
Happy 4th of july.
Thank you.

Steve,
Gems said:
“I've heard of people having troubles with Bosch plugs and wires in the Impala's... They switched back to new OEM AC Delco plugs and wires...”

You said:
“Second Ac wires and plugs i had before and they was same like Bosch. I think new stuff everywhere same.”

NO, NO, NO!!!! Not "everywhere same"!!!! Not anymore, like 10 years ago new platinum plugs would improve performance. Now, tight engineering tolerances determined by computer during design phase of engine demand only original equipment parts be used in this area!!!

bnaylor said:
“I agree with Gems. You need to put the original AC Delco spark plugs and ignition wires back in (new). The Bosch ign. wires are not as efficient as the AC Delco Packard or Premium Silicone 7mm wires. The AC Delco has the lowest resistance per foot. Bosch plugs leave a lot to be desired.”

I have not seen you state anywhere since then that you changed back to original equipment plugs and wires.

I would STRONGLY suggest that you do that.

Check out my post here http://www.automotiveforums.com/vbulletin/showthread.php?t=354316 where I had a very similar problem. I didn’t go through as much money or time as you are right now, but my problem was fixed by OEM plugs and wires.

Man, by the number of times that I see people asking about this subject, I almost wish a mod would make the one I referenced above a sticky post.

Steve, try this before spending any more time or money!

Ogre

Hello forum. I check my compression and it showd all of them around 170-180psi. And i put my Acdelco wires and plugs and still the same thing. One thing i cant do, cant find backpressure gage(my local AZ dont cary that). My previos post, i ask about heat issue, when car is cold i still have missfire but i have a lot of power, soon as it gets hot then i can feel shifting and major loss of power, maybe somebody familiar with that. Already i change a lot of stuff and cant think nothing else. About injector its gonna be strange if they cloged( sinse i bought it iam using 93 gas"always" and tried two times cleaner).What functions of resonator? Maybe iam gonna remove it like my cat and plus u bend too. I just dont wanna loud noise. Please help(spend alredy 3400$ for nothing). If somebody new in the post, look at this. This stuff was changed: Air and fuel filter, Maf sensor, Map sensor, purge control valve, IAC snsor, Air intake temp sensor, trothle position sensor, Wires and plugs(ACdelco), PCV, Cat is removed.
Symptoms no power, hard shifting, feels like missfire. No SES light. 2003 impala3.4, 87000. Thank you. Happy 4th of July

Forgot to tell vacuum and fuel pressure was checkt and its fine.

Question to Ogre73. Do you had hard shifting with that? Or only loss of power? If you had then i can take another shot to change them again( maybe i got bad ones, thing is happens you know).

Hello forum. ...And i put my Acdelco wires and plugs and still the same thing. ...If somebody new in the post, look at this. This stuff was changed: ...Wires and plugs(ACdelco), ...
Steve,
So did you put in the old plugs and wires, or did you go and get new ones? If you put in the old ones, I would suggest that you go get new ones.

Hey, you need to start looking at this a little more broadly. Big picture. Engines need three things to run: Fire, Fuel, and Air.

Look at them as systems unto themselves.

Troubleshoot using a "half-split" method. Check the input. If good, check the output. If bad, check half-way in between.

SO,
Fuel: The input seems OK, as you seem to be getting fuel through to the injectors. Testing the fuel pump (input) is essentially the same as testing the output. Check the output by checking the pressure of the fuel injection. This can be done with a gauge you should be able to get at AZ.

Air: Easy enough, check the input tube that goes to the air filter box, and check the filter. Since you have already changed the IAC sensor, you have been all around that area of the system. You probably would have seen any major blockages by now. I don't think you have any problems getting air to the engine.

Fire: It starts in the coil pack. It ends in the spark plugs. The fact that you are getting a more pronounced and worse misfire when warm makes me wonder about the coil pack. Have you had it tested under load? When cool and hot? On my Windstar, I had a nasty crack in the adhesive under the coil pack, that got larger and allowed more arcing when it got hot.

Check the input of the Fire system by having your coil packs tested under load. Just checking the resistance when cold will not always tell you if something is wrong. Also, just remove the two bolts holding each pack down and remove them. Visually inspect them, and make sure to use something to scrape the contacts and clean them. Use dielectric grease to keep the continuity good and protect from corrosion, then re-assemble.

When you can be certain that the input of the Fire system is good, then check the output.

Ogre

Good info. About spark plugs i put my old ones. OK. I am gonna change then this satturday. About coil, resistanse is fine. So for now we gonna stop on sparks and wires.
Question before. What functions of resonator? Cause probably i have restriction too. I just cant find that gage.
Another one. I am in NY brooklyn, do you no any stores open satturday, where i can find ACdelco sparks and wires, and probably iam gonna replace Fuel pressure regulator too.
Look what i think. GM checkt my exhaust back pressure. I think they open first Oxygen sensor and connect thegage. But it shows only restriction of exhaust( cat can be fine). But when you gonna check fron second oxygen sensor you can find it for sure, exhaust or cat. Pressure should be same on bank1 and bank2. I am not talking about 1.25 psi. I am just think they check only exhaust not specialy CAT. So i wanna remove that f$#@%king (thatf$#@%king) thing, i just dont wanna loud noise. Any info would be apreciated.
Most of my testing i was doing on cool engine, so they can be little bit off. Thats why i wanna replace Fuel pressure regulator.
I dont have enought time to order and shipping by this friday, so maybe you know any ACdelco stores where i can get all this. I used to order form Texas, but its gonna take 4-5 buss. days.
Thank you again.

Can you tell me more about fuel input and output. Cause i now only one way (cap near the generator) It was 56 or 57 i dont remember. Forgot to ask do you remove you fuel pressure regulator your self. I mean do i need some special tools for that or its pain in the butt? Can i do my self. 3.4 2003 87000
Steve

Can you tell me more about fuel input and output. Cause i now only one way (cap near the generator) It was 56 or 57 i dont remember. Forgot to ask do you remove you fuel pressure regulator your self. I mean do i need some special tools for that or its pain in the butt? Can i do my self. 3.4 2003 87000
Steve

Don't waste your time and money. The fuel pressure spec. is good. Plus you do not have any symptoms of a bad fuel pressure regulator.

For the spark plugs you can use AC Delco Iridium 41-101 gapped at .060. For ignition wires use AC Delco Premium Silicone 7mm.

I found some data on the 3.4L that may or may not be helpful to you. Some people experienced high and repetitive failures on their CAT convertors due to misfire. The cause was the ignition control module (ICM) and possibility of one or more coils.

Do us a favor stop wasting money and try to stay focused on the good suggestions from everyone that weighed-in, otherwise we may be at this another few months. :uhoh:

OK. Thank you. Let me see what i can do.

Hi guys. I put New ACDELCO wires and plugs and still the same thing. Bob you told me something about ICM. How i can test that, and what is that, plate under the coils or what? Coils resistanse is good. And one more thing i wanna ask 3rd time, if iam gonna remove resonator and U-bend my car gonna run louder or same? Cause i have 1000% CAT symptoms. Local shops (morons) dont have gage. AZ too. Thank you for your time. I wanna pay any money to fix that, maybe somebody closer to NY.

Forgot too ask. My father think its timing problem. BUt i told him that timing cant be ajust. Is there anything that can cause late timing (i not talking about chain) i am talking about crankshaft and camshaft and more i am pointing to that one wich right under the exhaust manifold (on the block, on the rear).

Description and Operation
The CMP sensor signal is a digital ON/OFF pulse, output once per revolution of the camshaft. The CMP sensor does not directly affect the operation of the ignition system. The CMP sensor information is used by the PCM to determine the position of the valve train relative to the crankshaft position. By monitoring the CMP and CKP signals the PCM can accurately time the operation of the fuel injectors. The PCM supplies the sensor with a 12-volt reference, low reference, and signal circuit.