engine messing up

Asked by Apr 29, 2016 at 10:18 AM about the 1996 GMC Sierra 1500 C1500 SL Extended Cab SB

Question type: Maintenance & Repair

Ok i have a 1996 gmc sierra with the 5.7L vortec
and just the beginning of this week it started
misfiring so i took it home til i got paid well i
replace my spark plugs, plug wires, distributor rotor
and distributor cap, i also put some chevron fuel
injector and system cleaner in it and i also pulled
my egr valve off it was still good but i went ahead
and cleaned it up and it still misfires, rough idling,
loss of power, and now its making a sound where it
sounds like its trying to release l. Can any of yall
help me out on trying to figure out why its acting
this way

9 Answers


Possible causes - Faulty spark plug - Clogged or faulty fuel injector - Faulty ignition coil - Fuel injector harness is open or shorted - Fuel injector circuit poor electrical connection - Ignition coil harness is open or shorted - Ignition coil circuit poor electrical connection - Insufficient cylinder compression - Incorrect fuel pressure - Intake air leak

I checked my all the spark plugs i cbecked its not a clogged injector or faulty injector nor the injector harness ill have to check coil and circuit poor but its just been very confusing and annoying atm and i was trying to get it done before today but thats not going to happen ill check everything again and see but hopefully what you told me helps out


Are there any codes? Check engine light on? If so get the code read.

No check engine light and i pulled the codes its saying egr valve but the valve is still good and i also cleaned it up


Ok, in reading your post, you say "its making a sound where it sounds like its trying to release l." So if you could elaborate more on what that sound is. Thinking the cat at this point, which if plugged could throw a EGR valve code.

I work at a dealership and i pulled the codes but the only thing popping up is egr valve but when i replace plugs wire cap and rotor i pulled the egr valve off and it was still good just needed a little cleaning so i cleaned it up but when i start my truck its makes this sound like air is trying to be released out i said something to some of the techs here and they said it could be the throttle body manifolds or something along those lines


Ok, a plugged cat. sounds like it is releasing air, but you would be able to tell where the sound is coming from out of the exhaust. So they must be talking about a vacuum leak. What you could do is when the engine is cool, then have it at an idle and spray some carburetor cleaner along the intake manifold gasket, around the throttle body, anywhere there is vacuum. If the rpm of the engine picks up, then you found a vacuum leak.

Ok sweet thabk

Thank you bud and if i have a vacuum leak and fix it and it doeant fix anything else looks like im going to be ripping my motor apart and fixing everything

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