I've got a 91'5.7L z-28, it slowly started to lope, like a cylinder is not firing. I've cheched the plugs and wires,rotor,cap and the injectors are working,I put in a new O2 sensor,and IAC, checked all the hoses. I'm at a stand still. I think its the head gasket.

 

White smoke out the tail pipe is a good indicator. You can also smell coolant in the exhaust. Plugs that foul quickly is also an indicator.
bsa

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"If they do not run, Then they will die." - Stonewall Jackson
#3
'87 IROC, 355 TPI, Converted to SD, 700R4, B&M Megashifter, 3.42, Trick Flow Twisted Wedge Heads, Edelbrock Intake, Accel Runners, Comp Cam, Crane Gold rockers, Lucas 24# injectors, Edelbrock headers, Flowmaster 3'' exhaust, Mallory Ignition, Transgo Performance Shift Kit, Corvette Servo, 2,000 Stall Torque Converter

 

Plugs would not foul quickly with a broken head gasket, quite the opposite iirc. Look for coolant in your oil and very clean plugs.

 

What about blue smoke? What's that mean? Sorry, I always thought that was for head gaskets, lol.

 

Blue smoke is oil, so most likely valve seals or piston rings.

Or a James Bond car.

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89 iroc-z 305 tbi
k&n filtercharger, open element air filter. nuffin' else

 

Also, bubbles in the radiator at the filler neck with engine idling can indicate compression leaking pass the headgasket into the coolant.

White plugs getting 'steam cleaned' and/or white smoke from the tailpipe.

A compression test (or preferably a leak down test) will show it too.

Jake

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1986 Corvette Coupe, 415 CID, Edelbrock 6073s, ZZ9