Service Engine Soon Light

pete44 · #1 03-07-2011, 06:14 PM

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

jdmccright · #2 03-08-2011, 11:58 AM

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!

pete44 · #3 03-09-2011, 11:01 AM

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

MT-2500 · #4 03-09-2011, 12:38 PM

Quote:

Originally Posted by pete44

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.

pete44 · #5 03-09-2011, 03:21 PM

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

MT-2500 · #6 03-09-2011, 04:42 PM

Quote:

Originally Posted by pete44

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.

j cAT · #7 03-09-2011, 08:51 PM

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].

pete44 · #8 03-10-2011, 03:53 PM

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

MT-2500 · #9 03-10-2011, 04:12 PM

Quote:

Originally Posted by pete44

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

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.

j cAT · #10 03-10-2011, 06:52 PM

Quote:

Originally Posted by pete44

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.

MT-2500 · #11 03-11-2011, 06:08 AM

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.

pete44 · #12 03-11-2011, 03:20 PM

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

MT-2500 · #13 03-11-2011, 04:06 PM

Quote:

Originally Posted by pete44

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.

j cAT · #14 03-11-2011, 08:05 PM

Quote:

Originally Posted by pete44

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

that is very funny !

pete44 · #15 03-18-2011, 08:14 AM

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

Thread Thread Starter Forum Replies Last Post

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Service engine soon light. Engine codes	RK4332	Grand Marquis	2	09-20-2006 04:55 PM
Steering wheel locked up, Service Engine Soon light, Flickering head lights	AnimalDrMarshall	Aurora	2	06-01-2006 11:49 AM
89 camaro engine trouble...service engine soon light	Cbballplaya	Camaro Discussions	17	10-24-2004 05:02 PM
service engine soon light	IDHITIT	S-10	7	03-31-2004 07:05 PM
Service Engine Soon Light and Service Light	bowmanslandscaping	SC/SL/SW	3	05-03-2003 03:43 PM

POST REPLY TO THIS THREAD