1992 Chevy Corvette missfiring above 400 RPM

Tiny
ALANSMOAK
  • MEMBER
  • 1992 CHEVROLET CORVETTE
  • V8
  • 2WD
  • AUTOMATIC
  • 43,000 MILES
Just Replaced; new distributor(AC Delco) new plugs, new wires(AC Delco) new ECM, new fuel filter, new fuel pump with new screen, new coil. Misses when idling at 850 and you pat the gas, pulls strong up to 4,000 in gear then it startes running on 7 cylinders and pops back thru the intake. At 5700 it shifts and will instantly pull strong again until you get to about 4000, 4100 and it starts missiing and poping again. We replaced all the item listed above and even ran a fuel pressure test. Still misses. I'm at a loss. Any help would be greatly appreciated. Thanks Alan
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Tuesday, December 15th, 2009 AT 3:22 PM

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Tiny
RASMATAZ
  • MEMBER
Oxygen sensor
Dirty fuel injectors (cleaning the injectors often fixes this).
Bad MAP (manifold absolute pressure) sensor
Bad TPS (throttle position) sensor
Bad or dirty MAF (mass airflow) sensor
Low fuel pressure (leaky fuel pressure regulator or weak fuel pump)
Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve)
Bad gasoline (fuel contaminated with water or too much alcohol)

Sometimes, what feels like a hesitation is actually ignition misfire rather than lean misfire. The causes of ignition misfire may include:

Dirty or worn spark plugs
Bad plug wires
Weak ignition coil
Wet plug wires
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Tuesday, December 15th, 2009 AT 3:31 PM
Tiny
ERNEST CLARK
  • EXPERT
If you don't mind, I'd like to add a word or two.

First, who replaced all of those components? If this was a shop, then I suggest you never work with them again, as this is an extremely unprofessional practice.

If you've done the work yourself, then I'd like to advise that's it's never a good idea to hunt for problems by replacing parts, because it never works and only costs big bucks.

Now, as for diagnosing a misfire (ignition or lean), rasmataz basically gave you the areas in which to look. But always begin at the simplest and work your way to the more complicated stuff. And when you suspect a faulty part, test it before buying another one and replacing something that wasn't bad to begin with. (Why I recommend not working with the mechanics who replaced your other parts)

Real technicians inspect before replacing. We know there's no pot of gold at the end of a rainbow.
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Friday, January 22nd, 2010 AT 8:58 PM

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