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2001 Chevy Cavalier Rough idle

Tiny
KMAN522
  • MEMBER
  • 2001 CHEVROLET CAVALIER
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 106,000 MILES
Guys hopefully you can help me. I have a 2001 Cavalier 2.4L. I recently had the water pump replaced due to it leaking and now after I picked it up from the repair shop it idles worth a darn. I never had this problem before. Idles very rough almost like it is running on 3 cylinders. When I drive it down the road it seems fine. I have checked for vacuum leaks and found nothing. I even sprayed the area with carb cleaner while running to try to detect the hidden vacuum leaks and still nothing. I changed the plugs which seemed to help a little but not fix the problem. I dont think my car is equipped with a EGR valve? Everything I read points to this but I am thinking my car doesnt have one? I checked the IAC motor and it moves in/out when the key is turned.

I have no codes on. I also cleaned the throttle body which was dirty still rough idle and hesitation once I start moving. I did unplug the mass air flow sensor when it was running thinking it might get worse and it didnt. I am thinking about replacing that for $12.

I am at my wits end with this thing. HELP.
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Sunday, March 29th, 2009 AT 7:19 PM

14 Replies

Tiny
JAMES W.
  • MECHANIC
  • 2,395 POSTS
Well, you've already checked the first few things I would have suggested. With the engine at a warm idle, spray some of that carb cleaner directly into the intake via a vacuum port or any other opening and see if the idle picks up. This will tell us if it's a lean problem or what. Please advise.
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Sunday, March 29th, 2009 AT 8:30 PM
Tiny
KMAN522
  • MEMBER
  • 6 POSTS
I removed the boot from the air filter to the intake. I sprayed in some carb cleaner & it died. Seems to have an odor from the exhaust like it is rich? One thing I did notice is it really races from almost dying to a very fast idle for the 1st minute. It is idleing right now (running about 2 minutes) but I notice my fan for my radiator turns on right away. Never did that before either.

Going to take it for a ride. Will let you know what it does.
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Monday, March 30th, 2009 AT 12:54 PM
Tiny
KMAN522
  • MEMBER
  • 6 POSTS
After taking it for a short run, it still spits & sputters at a stop. Spraying carb cleaner in the intake boot makes the car bog down. You can hear a definte spit/sputter sound coming from the exhaust if you stand behind the car. Sounds like it is running on 3 cylinders.

I also notice the radiator fan is now not on & I think it would be with the water temp up around the 195 mark?

This car has no EGR nor mass flow air valve. Stumped?
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Monday, March 30th, 2009 AT 1:10 PM
Tiny
JAMES W.
  • MECHANIC
  • 2,395 POSTS
OK, good job of testing. From what you've done so far, it's not running lean in fact, it sounds like it's rich. This rules out a vacuum leak. Next thing we have to look at is the IAC. When you checked it earlier, was the seat in the port clean and not carboned up? Try "creating a vacuum leak and see if that helps smoothen it out. I'm still real suspicious of the IAC.
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Monday, March 30th, 2009 AT 8:01 PM
Tiny
KMAN522
  • MEMBER
  • 6 POSTS
I did clean the IAC. Was a little dirty so when I took it out I did clean it. I talked to a well recommended mechanic & he tells me it sounds like the timing is off. Something about retarding the timing by even a tooth will cause the idle to be rough but not typically effect the car while running (higher rpm). Lower power at acceleration, which the car seems to have.

All I know is I dropped it off before the water pump service and ZERO problems with idle and now that the pump is changed idle problems.
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Tuesday, March 31st, 2009 AT 4:48 PM
Tiny
JAMES W.
  • MECHANIC
  • 2,395 POSTS
Let's take a look at what they would have fiddled with when they changed the pump. Check the sensor connections on the thermostat housing. Also, make sure the right connectors are on the right sensors. The statement you made that the fan comes on when you first start the car puzzles me.
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Tuesday, March 31st, 2009 AT 8:52 PM
Tiny
KMAN522
  • MEMBER
  • 6 POSTS
I will check those thoughts & let you know what I find. I really appreciate the help.
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Tuesday, March 31st, 2009 AT 9:25 PM
Tiny
KMAN522
  • MEMBER
  • 6 POSTS
I have found the problem. After bringing it to a recommended auto mechanic, he discovered the timing was retarted by 3 teeth. He put it back together and it runs like a top. Idles just as perfect as before.
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Sunday, April 5th, 2009 AT 6:47 AM
Tiny
JAMES W.
  • MECHANIC
  • 2,395 POSTS
I love it when a good plan comes together. Glad you found it. Anything else, you know where to find us.
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Sunday, April 5th, 2009 AT 12:36 PM
Tiny
MOOMOO
  • MEMBER
  • 4 POSTS
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Friday, April 10th, 2009 AT 12:31 PM
Tiny
MOOMOO
  • MEMBER
  • 4 POSTS
I'd like to know too. Mine does the same thing.(2001 Z24 2.4 156,000 miles) I get a code 300 and 171. 300 is multiple misfires, 171 is lean on #1 bank. I read that a 4 cylinder only has one bank. Hubby says a bad head gasket is allowing antifreeze to pour over spark plugs. And of course we are suspecting an air leak somewhere. We replaced the fuel injector pressure regulator, ran great for about 3 days. Then went back to poop! We are thinking of a new head gasket. Let me know if you figure it out.
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Friday, April 10th, 2009 AT 12:36 PM
Tiny
JAMES W.
  • MECHANIC
  • 2,395 POSTS
Try pulling out the IAC unit and plugging the hole with something that the engine can't suck in and see how the idle behaves. Everything you describe points to the IAC.
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Sunday, April 12th, 2009 AT 5:57 PM
Tiny
MOOMOO
  • MEMBER
  • 4 POSTS
Thanks for the advice, James. We will give that a try. Unfortunately my husband and I purchased a Pacifica today so my cavalier "ugly black Betty" is going to wait for a while. At least they didn't get her on the trade. I still love her, she was my blood sweat and tears (the payments-I bought her new).

Thanks again
MooMoo
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Thursday, April 16th, 2009 AT 9:32 PM
Tiny
JAMES W.
  • MECHANIC
  • 2,395 POSTS
Good to hear. If you have any future problems with either, you know where to find us.
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Thursday, April 16th, 2009 AT 10:51 PM

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