Mechanics

98 ROUGH IDLE

1998 Chevrolet Cavalier • 4 cylinder FWD Automatic • 205,000 miles

1998 cavalier 2.4l engine, at idle speed it is normal, then 20sec at idle it starts to sputter, and idle very rough. However there is no lack of power while the car is moving. Did a compression test, all normal, replaced camshaft and crankshaft position sensors. Changed spark plugs and the tiny wire connectors, still acting crazy, there is no check engine light. Any ideas?
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Ullyceese
March 20, 2011.




Clean the throttle body and iac. I always check for codes, regardless of lite, just habit, I guess. How long since a tune-up?

JDL
Mar 20, 2011.
Tuned up in oct 2010. Changed iac, tps, crank sensor, cam sensor. Checked both o2 sensors, ran injector cleaner through it got better for a day, but not perfect. Now back to same old thing as before rough idle when stopped. But a code did come up as bank1 running rich. Any ideas?

Tiny
Ullyceese
Mar 22, 2011.
Use a fuel pressure gage, see if pressure holds after pump stops. If no schrader valve, some models, you may have to use a special fitting to use gage. I can't remember without looking?

JDL
Mar 22, 2011.
Try this test, start the car, let it run for about 1min then shut it off, remover the vacuum line from the fuel pressure regulator and look for fuel in the vacuum line, there should not be fuel present in the line if you see or smell gas in it, then the regulator is bad. My 2.4l did this to me also, it would rough idle and try to stall sometimes. Dealer wanted to take the engine apart, I said no way and spent 6o bucks on dealer manuals from ebay.

Tiny
Ullyceese
Sep 29, 2011.
Sounds good to me.
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JDL
Nov 16, 2011.

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