stalling and backfiring

1992 CHEVROLET S-10
155,000 MILES • 4 CYL • 2WD • MANUAL
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MRCROWLEY64
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my 1992 chevy s10 2.5l is stalling at fast stops and backfires when shifting from 1st to 2nd and from 2nd to 3rd. if it doesnt stall when i come to a stop it will idle rough for a few seconds and then start to idle ok.ive done a complete tune up and done a timing check. retarding the timing made it run a little better and stopped it from backfiring as bad. the cat. conv. has been removed so its not a bad cat.
Feb 11, 2011 at 2:45 PM
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KHLOW2008
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Is the Check Engine Light indicating and have you tried to retrieve for trouble codes?

Was any major repairs carried prior to this occurring?
Feb 11, 2011 at 3:49 PM
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MRCROWLEY64
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no check engine light. no major repairs. first generation OBD
Feb 11, 2011 at 6:26 PM
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KHLOW2008
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I would suggest getting the fuel pressure and ignition related components checked.

There could be a fault with the idling circuit as you mentioned stalling during sudden stops. Get the throttle body and

IAC cleaned to see if the stalling goes away.

What is the idling speed after warming up?
Feb 11, 2011 at 6:34 PM
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MRCROWLEY64
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the fuel system is going to be my next check. i cleaned the throttle body and checked for vacuum leaks but i didnt clean the IAC. idle is fine when at operating temp as long as there is no sudden change in idle speed. when i come to a fast stop and disingage the clutch it will start to idle rough and will die unless i down shift. as long as the engine is under a load it idles and runs ok.
Feb 11, 2011 at 6:55 PM
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KHLOW2008
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A dirty IAC would cause erratic idling when there ia a sudden change so you should get it cleaned as well.
Feb 11, 2011 at 7:07 PM
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MRCROWLEY64
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do you like OBD2? it makes finding these kind of problems alot easier. i am going to do a complete fuel system and idle circuit check and clean the throttle body better and pull out the IAC and clean or replace it.i could do a vacuum leak check too couldnt i? what is the best way to check for vacuum leaks?
Feb 11, 2011 at 8:22 PM
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KHLOW2008
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The best way to check for vacuum leaks would be to use an aerosol carb cleaner or gumout spray. With engine running, spray near suspected vacuum leakages area and id the engine idling speed changes, there should be a leak.

OBD-II is more accurate and precises in their diagnostics. Pre OBD-II only tell you something is wrong but is not precise. Most codes would show as one but for OBD-II, it would show you lean or rich if it is anything to do with running conditions.

.
Feb 11, 2011 at 8:36 PM
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MRCROWLEY64
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thanks for all your help and if i need any more advice ill get back with 2carpros and ask for you. thanks again and God be with you.
Feb 11, 2011 at 8:51 PM
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KHLOW2008
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You're welcome.

If you require anything further, just post reply here and I would get back to you once I am online.

Have a nice day.
Feb 12, 2011 at 11:13 AM