92 GM sonoma loses power after warm up HELP!

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I have a 92 GMC sonoma with V6, 5-speed manual, 174k miles. everything has worked fine up until now. when the engine is cold, the truck drives perfectly. however, when the engine has had time to warm up and i have driven about 2 or 3 miles, the "service engine soon" comes on and the there is a BIG loss of power. also, when the engine light is on, and the truck has lost power it starts to shake like its trying to stall, but never actually stalls. the problem occurs with the AC on and off. I read that the catalytic converter could be to blame, or possibly the fuel pump. any help would be very appreciated.
THANKS!

posted by  everyone

I don't quite get to Tuscaloosa or Birmingham but I do get over to Muscle Shoals occasionally. Dales is a good steak house near Sheffield/Florence

Need to pull the trouble codes first.

posted by  tbaxleyjr

so im assume that would require me to go to the GM dealer? how much would a code scanner cost?

posted by  everyone

you dont need a scanner for a 92

http://www.autozone.com/servlet/UiBroker?ForwardPage=az/cds/en_us/0900823d/ 80/12/39/d6/0900823d801239d6.jsp

read through this and follow the links to ALDL and trouble codes - all you need is a jumper wire or a paper clip

posted by  tbaxleyjr

Yes the trouble code will tell you exactly whats wrong.

This sounds to me like an EGR problem btw also based on your description.

The error code, then the problem. It could also be the oxygen sensor overheating.... Its almost certainly something in the emmission system.

[edit]Oh yes it could be the catalytic converter also or muffler. Most likely it is EGR valve but sounds like exhaust is plugging up somewhere good luck come back with error code description[edit]

posted by  stamar

Once everyone comes back with his trouble codes (he will have some since the check engine light is on), all of us can help him determine the appropriate testing and diagnosis to determine the root cause of this problem. I would rather us do that instead of throwing parts

posted by  tbaxleyjr

egr comes on the moment the engine does (and you leave idle and are not wot)
and the cat wouldn't be a warmup problem it'd be from the moment the engine is started
if its a warm up issue its:

o2
ignition coils
thermostat
fuel pump is highly possible(replace filter at same time)
(its late I'm tired I'll add more to this list tomorrow sry sleepy time)

posted by  Pieface

or....

spark-plugs not gapped properly, fuel injection system problems, etc...

There will be some codes since the service engine light comes on. You can replace all of the parts on a car or you can pull the trouble codes and determine where to start looking for the problems.

posted by  tbaxleyjr

DEFINITLY need trouble codes first BUT.....Egr does not engage at idle, does not engage upon fairly heavy acceleration and does not engage at WOT. IF this system is electronically controlled by a vacuum switching valve or sensor that is fauled up, you could still have an EGR issue but not likely. The only reason there would be a loss of power and stumbling would be EXCESSIVE EGR flow causing the fuel/air mixure to be too Diluted with air ie) exhaust. If the EGR valve was stuck wide open or TOO much open, the problem would be there from the start-up. I also concur that if there was a cat. conv. issue it would be from the time the engine was started. That is not the issue unless for some strange issue is going on with thermal expansion when it gets REALLY hot.....NOT LIKELY at all....bout the same odds as a snow ball's chance in hell.

Other than that, if the light comes on ALWAYS scan the codes.....till you do you're waisting your time. It could be ANYthing....We'll see what he comes up with!

posted by  cmeseadoin

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