Service Engine Soon Light

Hello.

Having issues for awhile with my 1992 C1500 5.7L Chevy pickup. It has had a rough idle and "stumbles" below 1500 rpm (inwhich I shift it to D to get it out of overdrive) I did some meter checks (by Haynes manual) and changed out the TPS and the MAP sensors (which metered bad)...It runs a little better but still has the "stumble" at low rpm's in overdrive. My SES (service engine soon light) comes on for 10 to 12 seconds then goes off for 10 to 12 seconds in a cycling mode. I looked at distributor (under cap) and it is nice and dry. Plug wires are good and seated. I have developed a small oil leak that seemed to happen when my truck started running bad. (Thats what had me check under the distributor cap). I am going to AutoZone in the morning to see if they can pull some codes..Any suggestions?

Thanks,Pete

Check for vacuum leaks. Grab a can of carb cleaner and spray around the vacuum lines, TBI base, and breather hoses while the engine is idling. If it stumbles, you found a leak.

Also check the thermostatic air diverter in the air cleaner snorkel. If it's stuck shut it draws in hotter air from the exhaust manifold, which is less dense, creating a rich mixture that the ECM isn't expecting.

Finally, have the ECM scanned for codes anyways. Even if the SES light is off it will store past codes in memory. You can jumper between two OBD terminals to extract the codes...check a repair manual for the correct ones. There's also a sequence to reset the codes, too, to be sure the codes are recent.

Hope this helps!

OK, I went ahead and carried it in to have codes checked at a shop.(Since a '92 is too old to have checked at Advanced Auto or AutoZone)..It came back with:

Code 22 (TPS too low)
Code 32 (EGR System Problem)

I have already replaced the TPS . So they could have read a history alarm. I HAVE NOT replaced the EGR. I did the EGR test (plugging vacuum line to it) and it made no change to rough idle. Mechanic at shop said it would not be that anyway. This leads to yet another possibility..The ECM???...Haynes said it is under dash but mentions nothing about testing it...Has a chip inside so I am assuming you can replace chip or whole ECM.By Haynes code chart it mentions ECM wiring or replace for these issues...Any more thoughts?

Thanks, Pete

OK, I went ahead and carried it in to have codes checked at a shop.(Since a '92 is too old to have checked at Advanced Auto or AutoZone)..It came back with:

Code 22 (TPS too low)
Code 32 (EGR System Problem)

I have already replaced the TPS . So they could have read a history alarm. I HAVE NOT replaced the EGR. I did the EGR test (plugging vacuum line to it) and it made no change to rough idle. Mechanic at shop said it would not be that anyway. This leads to yet another possibility..The ECM???...Haynes said it is under dash but mentions nothing about testing it...Has a chip inside so I am assuming you can replace chip or whole ECM.By Haynes code chart it mentions ECM wiring or replace for these issues...Any more thoughts?

Thanks, Pete

Proper testing.

Always clear codes and see what returns.
Also what transmission you have?
On code 32 if it returns.
And you have a V8 with no 4L80 transmission.
Key on engine off ground pin A to pin B on diagnostic connector and see if egr solenoids activates to allow vacuum threw it to egr valve and egr valve opens and holds vacuum.

Also with egr valve open and engine running it should give a rough idle with egr valve open.

To get egr open you have to apply vacuum to it or reach in it and open by hand.

Run these test and let us know what it does and what codes returns after code clear.

Thanks... I tried before to move the EGR by hand and it was nill to none by movement. (read somewhere that it should be pretty easy to move)..The tranny I have is the 700r4...I am still suspecting the EGR but the ECM is lurking in the background to be the culprit.

Pete

Thanks... I tried before to move the EGR by hand and it was nill to none by movement. (read somewhere that it should be pretty easy to move)..The tranny I have is the 700r4...I am still suspecting the EGR but the ECM is lurking in the background to be the culprit.

Pete

Run the proper test before throwing ECM at it.
Have you cleared codes and checked for what comes back.
Have you done the egr valve solenoid test?
Most egr valves should open by hand.
If not put a good vacuum on it.
When it opens it should almost stall engine or cut idle way down.

I am not saying this is your problem ........

I have alot of experience with these EGR valves and intake EGR passage ways that have issues.

to say a bad or improperly operating EGR cannot cause your problem is not correct..................

the valves can fail many ways , sometimes the intake causes this also.

stumble on acceleration could be a weak EGR spring as just one example .

EGR is calibrated to produce a set amount of exhaust gas into the combustion chamber . too much you get a stumble [not enough oxygen].

Thanks for the replies....The shop I took it to cleared the codes only for the "service engine" to come back...They basically hurried me out of there (5 minutes) but it was free. They told me to come back in a week to re-read the codes again.. I went to Auto Zone and they have an OBD1 analyzer. Not much to it ($35)..Don't even know if it would even clear my codes. I have plugged the EGR vacuum line (going to EGR) and no change in engine idle. (still rough)..I have a vacuum tester and will perform placing vacuum on EGR. I saw an online site that has ECM ($100 and up) that I bookmarked. EGR I looked at around half that price...If the ECM was bad I assuming it would throw a code ?

Thanks, Pete

Thanks for the replies....The shop I took it to cleared the codes only for the "service engine" to come back...They basically hurried me out of there (5 minutes) but it was free. They told me to come back in a week to re-read the codes again.. I went to Auto Zone and they have an OBD1 analyzer. Not much to it ($35)..Don't even know if it would even clear my codes. I have plugged the EGR vacuum line (going to EGR) and no change in engine idle. (still rough)..I have a vacuum tester and will perform placing vacuum on EGR. I saw an online site that has ECM ($100 and up) that I bookmarked. EGR I looked at around half that price...If the ECM was bad I assuming it would throw a code ?

Thanks, Pete

:nono::nono: on bad ECM throwing code.

A 2 bit paper clip will show codes.
Just jumper pin A and B on the diagnoist connector and read flashes on check engine light.
Battery cable disconnect will clear codes.

You need to put vacumn on EGR valve to test it.

Pluging EGR valve does not tell you aything but may set a code.

Do the proper testing before throwing parts at it.

Bad ECM does not usually throw a code saying it is bad.

Thanks for the replies....The shop I took it to cleared the codes only for the "service engine" to come back...They basically hurried me out of there (5 minutes) but it was free. They told me to come back in a week to re-read the codes again.. I went to Auto Zone and they have an OBD1 analyzer. Not much to it ($35)..Don't even know if it would even clear my codes. I have plugged the EGR vacuum line (going to EGR) and no change in engine idle. (still rough)..I have a vacuum tester and will perform placing vacuum on EGR. I saw an online site that has ECM ($100 and up) that I bookmarked. EGR I looked at around half that price...If the ECM was bad I assuming it would throw a code ?

Thanks, Pete

take the EGR off the engine . make a plate to block off the ports. see if the engine idles better.

To add to Jcats pull EGR valve.
Good time to have a good look at the EGR valve.
Check for being stuck open or carbon under plunger keeping in from closing.
Alos a put lips over plunger hole and give it the old nasty suck on it test to see if it is sealing closed.
If you do not have a cover plate for egr valve holes put masking tape over suction hole and leave exhaust hole open.
Start engine and see if idle is better.
Let us know how it goes.

Crazy question...How do you know which one is the exhaust hole and which one is vacuum hole?

Crazy question...How do you know which one is the exhaust hole and which one is vacuum hole?
Very easy to tell when you start engine.
Just Fire it up.
The vacuum hole will have engine vacuum.
And engine will run like crap untill you plug it.
And exhaust hole will spit out ehaust.
Plug vacuum hole and see fhow it runs.
Let us know how it does and be suer to check EGR valve when it is off.

Crazy question...How do you know which one is the exhaust hole and which one is vacuum hole?


that is very funny !

Update:

I checked my EGR and my EGR Solenoid by applying vacuum.Both OK.EGR with applied vacuum made engine idle worse and EGR solenoid held vacuum fine (no leaks) Still suspecting ECM..Any more thoughts? I am going to try and run by shop today to check codes again..They cleared them over a week ago..

Thanks again, Pete

From what you describe, it sounds like the EGR is stuck open, but there's no response post that you checked for other vacuum leaks which can also cause intermittent stumbling and hesitation when accelerating.

[EDIT]
I forgot to mention the possibility of the IAC valve being stuck as well, even though it doesn't show up on your code reader. If it doesn't open at idle like it should or operate correctly it too can cause poor idle and stumbling.

The way I read the initial question is it only runs bad in overdrive, by that I assume when you drive and are coming to a stop it runs bad then switching to drive clears it up. Or is it bad just starting it up and going into OD? If it is only when coming to a stop in overdrive I might suspect the lock up converter sticking, going to drive forces the lockup off. Or did I read the question wrong?

The way I read the initial question is it only runs bad in overdrive, by that I assume when you drive and are coming to a stop it runs bad then switching to drive clears it up. Or is it bad just starting it up and going into OD? If it is only when coming to a stop in overdrive I might suspect the lock up converter sticking, going to drive forces the lockup off. Or did I read the question wrong?




he says on his first post of his issue:
Having issues for awhile with my 1992 C1500 5.7L Chevy pickup. It has had a rough idle and "stumbles" below 1500 rpm .

what he needs is to buy some equipment to properly troubleshoot this. so far he has given no details on HIS findings ..very vague !

if he has a bad vacuum or a failed EGR it will idle like crap and shift erratic.

Update again: Will try to be more specific. It is like jcat said need better diagnostic tools. Here is what I have done so far:

checked EGR (with vacuum gauge-applied vacuum engine went from slight stumble to rough stumble to nearly dieing)

checked EGR solenoid (placed vacuum on intake line (from carb)..It held vacuum fine-NO LEAKS)

looked/poked around vacuum hoses..nothing obvious or loose

I have replaced:
TPS- I went by Haynes manual to check for voltage increase with throttle increase..It had a .06 volt and stayed at that..no voltage increase with throttle..



MAP...same thing..took voltage readings according to Haynes procedure..found nill to no voltage...So I replaced



Looking at now:BUT Haynes say to take it in to shop to check properly

IAC...Check resistance over four terminals on it according to Haynes
ECM...The HEART of everything..No way for me to check...Just replace..$100 and up


Codes I get is:

22...TPS too low
32... EGR System problem

*** Just a note..AutoZone has an OBDI1 tester for $30 to $35 dollars...AutoZone or Advanced Auto cannot diag anything below a 1996 year.***
Thanks again to all replies and help!

Pete

Update again: Will try to be more specific. It is like jcat said need better diagnostic tools. Here is what I have done so far:

checked EGR (with vacuum gauge-applied vacuum engine went from slight stumble to rough stumble to nearly dieing)

checked EGR solenoid (placed vacuum on intake line (from carb)..It held vacuum fine-NO LEAKS)

looked/poked around vacuum hoses..nothing obvious or loose

I have replaced:
TPS- I went by Haynes manual to check for voltage increase with throttle increase..It had a .06 volt and stayed at that..no voltage increase with throttle..



MAP...same thing..took voltage readings according to Haynes procedure..found nill to no voltage...So I replaced



Looking at now:BUT Haynes say to take it in to shop to check properly

IAC...Check resistance over four terminals on it according to Haynes
ECM...The HEART of everything..No way for me to check...Just replace..$100 and up


Codes I get is:

22...TPS too low
32... EGR System problem

*** Just a note..AutoZone has an OBDI1 tester for $30 to $35 dollars...AutoZone or Advanced Auto cannot diag anything below a 1996 year.***
Thanks again to all replies and help!

Pete
Ton start with.
Pitch that haynes manual in the trash can and get some good repair info.

All Data has a good online DIY repair info system.
FOR TEST EQUIPMENT A VACUMN GAUGE AND A GOOD VOLT/OHM METER AND A ALL DATA diy ONLINE SUB.
The all data has repair flow charts for your code.
Go threw them and they will lead you to your problem.

And last thing a old paper clip to jumper pins A and B codes.

Update again:

Took it to a shop today and after 1/2 hour (and $35) they said it was an EGR problem...Mechanic said they just worked on a truck like mine and it ended up being HEAVY DEPOSITS in the throttle body area. He quoted me $600 to clean out throttle body..So, like most of us here I said thanks and went home and started out with a new PVC (it was clogged heavily) and cleaned out vacuum lines to carb from PVC. Tomorrow or better yet this weekend (if weather permits I will pull EGR and clean it and all other vacuum lines that need it) and while I am at it look into throttle body and shop vac it out..Mechanic did say this can be a "can of worms" the more you take it apart meaning SUT...Interesting though I mentioned the oil leak started same time my problem happened and he said "yeah, that happens with everything clogged up" otherwords oil being "pushed" out of seals..no aspiration..You know, funny thing is my oil pressure has been "higher than normal" since this has happened..Maybe he is making since in a way..Will keep you updated.


Pete

Update again:

Took it to a shop today and after 1/2 hour (and $35) they said it was an EGR problem...Mechanic said they just worked on a truck like mine and it ended up being HEAVY DEPOSITS in the throttle body area. He quoted me $600 to clean out throttle body..So, like most of us here I said thanks and went home and started out with a new PVC (it was clogged heavily) and cleaned out vacuum lines to carb from PVC. Tomorrow or better yet this weekend (if weather permits I will pull EGR and clean it and all other vacuum lines that need it) and while I am at it look into throttle body and shop vac it out..Mechanic did say this can be a "can of worms" the more you take it apart meaning SUT...Interesting though I mentioned the oil leak started same time my problem happened and he said "yeah, that happens with everything clogged up" otherwords oil being "pushed" out of seals..no aspiration..You know, funny thing is my oil pressure has been "higher than normal" since this has happened..Maybe he is making since in a way..Will keep you updated.


Pete
He quoted me $600 to clean out throttle body.:jerking:
600$ Was he wearing a mask? Like the masked bandit?
A tooth brush and a can of carb/throttle body cleaner and 15 minutes work will give you that 600$ clean up.
5$ for cleaner and 15 minutes work = 2395$ hr labor there.
Also.
Throttle body deposits will give you a higher tps reading not low.

Get a repair flow chart for the tps sensor code.
And go all of the way threw it.

On the egr valve do some proper testing and inspection of EGR valve passages.
And confirm EGR valve is working right like opening and closing good.

with the shops findings I agree on this can turn into a big mess..

your engine has a poorly maintained engine oil/crankcase system.

the PCV needs checking every year.. replacing this is required every 2 years when the vehicle does stop and go traffic..this valve can wear out or get plugged up by not changing the oil in the proper time/mileage.

vacuum lines need replacing not cleaning..................

Intake manifold could be plugged up ..this would require in some cases removal and acid wash...using a stiff wire and a shop vac you can try to open it up..throttle body will need to be removed to open this passageway..if plugged..


poor idle is PCV #1...then other components..measure engine vacuum WITH A GUAGE , and then start replacing hoses see what you get after ..

with the engine running at idle place a piece of paper over the oil fill hole...it should be sucking in....not blowing out ...blowing out means crankcase pressure and this is a bad PCV/VENT system...

this is why it leaked oil .

I agree..The engine in this truck is not original. I had a "rebuilt" one put in around 200,000 miles..It now has 280,000 miles..Shop man made a point by saying the engine rebuild place SHOULD have cleaned out the intake and throttle body.I change my oil every 5,000 miles..So point being said I will replace the EGR and the EGR solenoid. If no fix , I will be prepared to take apart and clean..( after my old car is ready for the road)This truck is a daily driver 36 miles a day to work...I changed all vacuum lines already. Wish me luck and again thanks to everyone!

Pete

I agree..The engine in this truck is not original. I had a "rebuilt" one put in around 200,000 miles..It now has 280,000 miles..Shop man made a point by saying the engine rebuild place SHOULD have cleaned out the intake and throttle body.I change my oil every 5,000 miles..So point being said I will replace the EGR and the EGR solenoid. If no fix , I will be prepared to take apart and clean..( after my old car is ready for the road)This truck is a daily driver 36 miles a day to work...I changed all vacuum lines already. Wish me luck and again thanks to everyone!

Pete

If you use dino oil , the oil and filter should be replaced at 4000miles max...also don't use fram filters and only drain the engine oil when hot at the normal operating temp. allow time for total oil drain ..with 80,000 on this engine and the PCV being plugged the oil is not being maintained correctly...could also be the thermostat is not allowing the engine to run at the correct temp..too cold will do it...