Jimmy acceleration problems

For the first 30 secs its runs great then under normal acceleration it starts running very rough. If I punch it it seems to clear up. If in nuetral it seems ok to just under load. Ive just change the temp sensor thinking the choke was staying on (didnt work) I also changed the O2 sensor(also didnt work) the truck has new wires plugs cap and rotor. The fuel pressure seems to be ok 2. CAN ANYONE HELP PLEASE.

Thanks in advance

BAGEL

what year, engine?

We need all information

its a 1990 model 2 door 4x4 automatic with a 4.3 V6

Check your timing.

Remeber to remove the timing wire from the computer under the dash.

The wire to disconnect is a brown and beige wire running under the carpet under the glove box.

Remove it, time the vehicle to zero with a timing gun and then reattach the wire.

I'll try it and let you know. If anyone has any more suggestions I'll be more than happy to listen...

Timing is dead nutz at 0. fuel pressure is perfect. Someone told me it could be the throttle position sensor? Any know anything else it could be or something else I can check?

Did you disconnect the timing wire while timing the vehicle with a timing gun?

YEs the wire thats under the glove box. I also looked it up on ALLDATA to find out were it was.

Anyone have any suggestions

Fuel Pressure?

Ever changed the fuel filter?

I' am just wondering if you found the problem, if not, is the SES light on?

I had the fuel pressure tested and it was good.
SRS light is not on.

What pressure did it show?

If i recall it was like 14psig. I looked it up on all data to get the tolerance and if im not mistaken it was 13-18 and i know it fell in that range. But remember when i first start it i can drive about 2 or 3 blocks and it runs great. I had another suggestion from a friend who said that Cat could be plugged????? but im not sure how true that is...

Did you check the operation of your EGR valve and the system? An easy way to tell if there is a problem there, is to disconnect the EGR valve. Pull the vaccum line that goes to the valve only, not anything else. See what happens.

I wonder if there are any check engine lights.

Ill check the EGR and let you know.

THERE IS NO CHECK ENGINE LIGHT ON

Checked EGR still does the same thing

Hmmm.....

Still makes me think the fuel pump is weak.

I have similar problem on my 89 Jimmy (4.3L / 145 k miles.) Haven't been able to solve it yet. Last recommendations was to replace engine. If you get yours solve - please let me know so I can try the same solution.

My 93 4.3 Vortec
was behaving very similar - seemed to idle find, but when accelerating it coughed and eventually got so bad that I can only drive 10mph.

I replaced:
fuel filter
Throttle Position Sensor
EGR Valve

ALL FOR NOTHING BECAUSE THE PROBLEM WAS THE SAME!

So I took it to a mechanic and he told me it is my CPI unit.
Cost me $120.
Now I am awaiting my CPI unit from an ebay seller ($180 vs. usual +350).
I don't have the experience to tell you that's your problem but it seems worth looking into. Can't tell ya how to diagnose it though.

Can anyone tell me why I can't find a Throttle Valve Cable near the accelerator/cruise control cables on the same lever?


greg

Can anyone tell me why I can't find a Throttle Valve Cable near the accelerator/cruise control cables on the same lever?


greg

The transmission is electroniclly controlled, there is no TV cable for these transmissions.

My 93 4.3 Vortec
was behaving very similar - seemed to idle find, but when accelerating it coughed and eventually got so bad that I can only drive 10mph.

I replaced:
fuel filter
Throttle Position Sensor
EGR Valve

ALL FOR NOTHING BECAUSE THE PROBLEM WAS THE SAME!

So I took it to a mechanic and he told me it is my CPI unit.
Cost me $120.
Now I am awaiting my CPI unit from an ebay seller ($180 vs. usual +350).
I don't have the experience to tell you that's your problem but it seems worth looking into. Can't tell ya how to diagnose it though.

Can anyone tell me why I can't find a Throttle Valve Cable near the accelerator/cruise control cables on the same lever?


greg

Remember to replace the nut kit as well.

Get it all done in one shot so you won't have problems in the future.

OK IGNORE THE ABOVE POST.
I discovered on another post that I must go to GMC dealer for the nut kit. Problem is the guy wan't very knowledgable, so I am going to attampt to find a # for the "internal line kit" - anyone know that?
I am not sure which clips I need to order. I have a few #'s I need to find a site w/ pictures to verify.

# for the "internal line kit" - anyone know that?

GMC called me back and tried to clarify this w/ me:

the internal line kit for a 93 gmc 4.3 w w/ CPI -
is this referred to as TBI Fuel Feed or TBI nut kit?

I thought TBI had nothing to do w/ CPI, but he says this is what I need, for $80.41. part # 17112705

any tips?

Go to the dealer and ask for the nut kit which is the internal fuel line kit for the CPI or CMFI injection system.

Better yet, walk in there and show them.

Go to the dealer and ask for the nut kit which is the internal fuel line kit for the CPI or CMFI injection system.

Better yet, walk in there and show them.


Do I need to be concerned about resetting my timing - after I put in the CPI and nut kit?

Does "IF IT AIN'T BROKE DON'T FIX IT" applly to my distributer cap & rotor, and plugs? These have not given me trouble but are probably from 1993 or late nineties at best?

gratzi

Do I need to be concerned about resetting my timing - after I put in the CPI and nut kit?

Does "IF IT AIN'T BROKE DON'T FIX IT" applly to my distributer cap & rotor, and plugs? These have not given me trouble but are probably from 1993 or late nineties at best?

gratzi

It would be foolish to fix the CPI and nutkit and have the fresh injection system being hampered by a vehicle that han't been tuned up properly.

Do a complete tuneup with cap, rotor, wires, AC Delco plugs gapped properly, PCV valve, fuel filter, air filter.

Also note, might want to do a cooling system flush with a new Non AC Delco rad cap along with a transmission flush and filter change and to drain your tranfer case and differentials and fill them with fresh fluids.

It might seem like a lot, but you can do most of it yourself and your truck will be completely perfect and performing to its maximum potential and will lengthen the life greatly.

Also, would be best to time the truck now AFTER everything is tuned up by pulling the brown and beige timing wire from the PCM under the dash, timing the veicle with a timing gun to zero, and then reconnecting the wire to the computer.

Be mindful that you might have some carbon coming out of your newly tuned up engine and you will have to clean the EGR valve out a couple of times when the excess carbon is released from the engine.

Might as well buy a couple of EGR gaskets just to make the cleaning easier.

[QUOTE=BlazerLT]...Do a complete tuneup with cap, rotor, wires, AC Delco plugs gapped properly, PCV valve, fuel filter, air filter.

Also note, might want to do a cooling system flush with a new Non AC Delco rad cap along with a transmission flush and filter change and to drain your tranfer case and differentials and fill them with fresh fluids.

Also, would be best to time the truck now AFTER everything is tuned up by pulling the brown and beige timing wire from the PCM under the dash, timing the veicle with a timing gun to zero, and then reconnecting the wire to the computer...

THANKS for the advice man. I purchased the the above parts and cheap AutoLite plugs.

Wanted to take care of that lastnight while I wait for my nut kit, but discovered some crackhead broke my window (probably saw me w/ my tools over the weekend). So I had other things to attend to.

The higherpowers playing a joke on me? The anti-GMC gods raging?

I'll try to get the truck running this weekend then figure out the flushes/fluids.

g

Take the cheap autolite plugs back and do the job properly with GOOD plugs.

AC Delco plugs are really cheap and are the best for our trucks.

Model # for your year is CR43TS gapped at 0.045

Don't go cheap on your truck parts or you will be sorry.

should i return the cheap-arse plastic $16 distro cap too?

All cap and rotors are plastic, no such thing as a metal cap and rotor other than the contacts.

A long days work has been fairly succesful.
Replaced:
CPI unit
Nut Kit
Distributor Cap, rotor, wires & plugs.
Fram Air Filter
Also replaced EGR, TPS, and fuel filter a couple weeks ago.
She sounds clean, BUT

there seems to be a subtle knock, not loud, coming from EGR area, or maybe valve covers. not sure what to make of that. the EGR is mounted onto a thread that snapped, I just put a nut on it - but had to grind part of the EGR base down to get the nut onto the short thread sticking out. when i first put this on the EGR did not want to mount flush. i wonder if the knock is just air seeping from the EGR gasket, or something else.

almost in over my head...
thanks for all input!

Oh god, this is not good.

Who knows but you should change your oil and your filter seeing your oil is probably full of gas from the CPI leaking.

My jimmy was doing the same thing, and it turned out to be the ECM under the distributor. One of the plug socket's was broke inside, sometime's it would run and other time's nuthin. The ECM has to deliver the right voltage to the fuel pump or it doesn't maintain enough pressure to run. The plug's in the back can break (the ECM itself) and cause fluctuation's, slow sluggish, stalls, and not starting.:banghead: It took alot of money and a great mechanic:smokin: to figure that one out.

My jimmy was doing the same thing, and it turned out to be the ECM under the distributor. One of the plug socket's was broke inside, sometime's it would run and other time's nuthin. The ECM has to deliver the right voltage to the fuel pump or it doesn't maintain enough pressure to run. The plug's in the back can break (the ECM itself) and cause fluctuation's, slow sluggish, stalls, and not starting.:banghead: It took alot of money and a great mechanic:smokin: to figure that one out.


How much is this part if I was to replace it myself, I'm having similar problems, random stalling then no start for about an hour, then runs fine for another day...

What was yours doing?


Anything like my problem?


http://www.automotiveforums.com/vbulletin/showthread.php?p=3321896#post3321896

Oh god, this is not good.

Who knows but you should change your oil and your filter seeing your oil is probably full of gas from the CPI leaking.

AFter replacing the CPI - four months later - the Fuel Pressure Regulator side of the intake is washed clean. Damn. I thought the 'new' CPI would take care of this. I'll try putting a new regulator on the allegedly new CPI unit. Could it be anything else I should look into while I have the intake exposed?

My Injector ELectrical Connector does not fit tight onto the top two pins of the CPI...any creative solutions for that besides tape it tight on the outside? Or besides spending ??$$$$ on a new one...

THe reason my EGR was knocking a while back was because it was not on completely tight - slight gap, it was just air rapping out of it. I'll spare the details.\

Thanks and good luck to all!

The grime in the upper plenum will take several thousands of miles to come back.

What you are seeing is the washing from the last CPI blowing.

The grime in the upper plenum will take several thousands of miles to come back.

What you are seeing is the washing from the last CPI blowing.

Sh#t. I mean, that's good, I guess. It's not good I just paid $50 a Fuel Pressure Regulator though...I guess it's a waste of time to put it in.

You're quite helpful I should send you a xmas card or something! In August.

cheers

I looked down my plenum to check a month ago and I thought the same thing until I llooked at the photos I took before I replaced it and the same markings and washed areas were there from the last one.