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92 chevy: cylinder..blowing..spark plugs, smoke was coming..idling

Customer Question

I have a problem with my 92 chevy s-10 2.5L 4 cylinder... it's blowing fuel backwards through the fuel injection and when i pulled out one of the spark plugs, smoke was coming from the inside... any help or suggestions?
i was driving along the road and it all of a sudden decided to run really crappy, almost like it sounded like a loud harley davidson idling
Submitted: 11 years ago.
Category: Car
Expert:  Davo replied 11 years ago.
 You need to check for compression on all 4 cylinders.You may have a mechanical problem from your description.If 1 cylinder is low you will know where to start looking.
Customer: replied 11 years ago.
Reply to Davo/diablo666's Post: how will i know if it's low? what makes it have low compression?
Expert:  Davo replied 11 years ago.
 You will be looking for about 125-150 psi per cylinder if one is way lower like 80 psi for example you have a problem and a wet compression test needs done to see if its rings or something else.
Customer: replied 11 years ago.
Reply to Davo/diablo666's Post: come to find out, it was the timing. timing's off on it. had a friend look at it and said 100% that it's the timing... gotta replace the timing belt :)
Expert:  Tech501 replied 11 years ago.

 I hope your friend isn't in the automotive business. No chains or belts in that engine






Click image to see an enlarged view
Fig. 1: Pressing the timing gear from the camshaft - 2.5L engine



 


Click image to see an enlarged view
Fig. 2: Use a feeler gauge to check thrust plate clearance once the gear and thrust plate are assembled to the camshaft




Expert:  Davo replied 11 years ago.
  A compression test would come up low if the valve timing is off.If it still runs I suggest you do the compression test before putting in a set of gears.The cam gear is a composite gear with a fiber type material and when they go they generally strip and it won't even start.
Customer: replied 11 years ago.
it BARELY starts takes a while for it to start though. he used to be a diesel mechanic. and he said he changed out the timing in his motor and he had a 91 chevy pick up. and said thats the exact sound it made.
Expert:  Davo replied 11 years ago.
 Its possible you could have an ignition secondary malfunction ie plug,wire,module or coil but I still would check compression first.I just replaced one of these engines for the exact same symptom.It had a golf ball sized hole in #4 piston.Didn't have any compression in #4 either.Its your choice test and eliminate possibilities or buy parts and hope they are the right ones.
Davo, Master technician
Category: Car
Satisfied Customers: 3253
Experience: ASE Master Technician/Advanced Automotive Diagnostic Technician
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Customer: replied 11 years ago.
lol, i guess i'll have someone come over that's a technician that i trust and see what they can say about it.
Expert:  Davo replied 11 years ago.
 If my information has been helpfull please click on the accept button.If you have further questions on this matter let me know I will answer them.
Customer: replied 11 years ago.
they didnt change over from belt to chain in 93?
although that's not really important.. if i had no compression, would their be smoke coming out of my exhaust or fuel blow back through the fuel injection?
Expert:  Davo replied 11 years ago.
 Depends on the type of failure.If you don't have a compression gauge you will be able to tell if you have a cylinder with zero compression by removing 1 plug at a time and firing up engine.If one doesn't make a loud air pop noise it has no compression.If that all passes you will have to get a compression gauge to continue.They are not expensive and can be used on any future vehicles you own.Autozone may even rent you one for a small refundable fee.Keep me posted until the problem is solved.
Customer: replied 11 years ago.
Reply to Davo/diablo666's Post: yeah, i sure will, no doubt, i'll have to get one of the compression tools from autozone.

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