98 Cavalier rough idle

Tiny
ULLYCEESE
  • MEMBER
  • 1998 CHEVROLET CAVALIER
  • 4 CYL
  • 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?
Sunday, March 20th, 2011 AT 1:49 PM

5 Replies

Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Clean the throttle body and iac. I always check for codes, regardless of lite, just habit, I guess. How long since a tune-up?
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Sunday, March 20th, 2011 AT 3:23 PM
Tiny
ULLYCEESE
  • MEMBER
  • 4 POSTS
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?
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Tuesday, March 22nd, 2011 AT 1:42 AM
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
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?
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Tuesday, March 22nd, 2011 AT 2:23 PM
Tiny
ULLYCEESE
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  • 4 POSTS
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.
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Thursday, September 29th, 2011 AT 12:11 AM
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Sounds good to me.
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Wednesday, November 16th, 2011 AT 9:13 PM

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