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Idling problem

Tiny
BONEMAN 69
  • MEMBER
  • 1995 PONTIAC FIREBIRD
  • 3.4L
  • 6 CYL
  • RWD
  • AUTOMATIC
  • 125,000 MILES
My car starts and runs great when it is cold. Once it start to warm up the idle will become erratic, it will sputter for thirty seconds or so then rev up to about 1500 rpm's then it levels out at about 950 rpm's, which seems high, this is when the car is in park or neutral. When it is in gear it will do the same, only if I turn the wheel a bit it, the sputtering becomes worse and the car will stall. I have replaced the IACV, TPS, and the coolant sensor. I also have a new catalytic converter. I have searched many times for vacuum leaks, but have found none. The car also has a hesitation when going down the road and seems to become flat at times, only to take off like a rocket. I seems to be using a lot of fuel and the gas mileage is down. The check engine light is on. I am confused at this point! Do you think I may just need a tuneup? The gas filter is new and the air filter is also new.
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Thursday, April 14th, 2016 AT 4:42 PM

9 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
First scan for codes you will need ot fid a pro that can do this one as auto parts cannot clean throttle plate on both sides and iac hole with choke cleaner and check fuel pressure with a gauge 41-47 psi key on only.
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Friday, April 15th, 2016 AT 7:05 AM
Tiny
BONEMAN 69
  • MEMBER
  • 6 POSTS
I forgot what code was, but I was told TPS, when I put a new one on the check engine light goes out, but the car runs even worse with a lot of smoke coming from the engine and it just goes right to a stall unless you keep your foot on the pedal. Did I do something wrong changing it? Seems to be pretty straight forward. So I put the old one back on and the check engine light reappears, the car runs better then it still sputters out. Is cleaning the throttle plate a hard job for a back yard mechanic? Not really sure where to start.
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Friday, April 15th, 2016 AT 6:22 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Anything I have sent you is fairly easy to do, we have an article on this site under how to repair under fuel to check pressure. Your tps may have an adjustment on it if the screw holes are slotted then it is not adjustable, also check for a vacuum leak it may have one and check for hoses that are cracks/broken etc.
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Saturday, April 16th, 2016 AT 6:10 AM
Tiny
BONEMAN 69
  • MEMBER
  • 6 POSTS
Thanks for your help I will let you know how it turns out. I really want this car to run good. It is a gem other than the idling problem.
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Saturday, April 16th, 2016 AT 3:48 PM
Tiny
BONEMAN 69
  • MEMBER
  • 6 POSTS
Found a hose that runs to the MAP sensor that was melted, never even knew it was there. It is made of thin plastic tubing with rubber fittings. Do I need to use the exact type of hose or can I put a regular vacuum hose in it's? I will have to alter the ends a little but will it still work the same?
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Sunday, April 17th, 2016 AT 4:43 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
A regular vacuum hose should last about 4-5 years or so. Replace it and it may run ok if not scan for codes to see if you get a map sensor code.
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Sunday, April 17th, 2016 AT 5:01 PM
Tiny
BONEMAN 69
  • MEMBER
  • 6 POSTS
I want to Thank-You for being so helpful and making me dig deeper. I looked at and wrote down every piece I needed to replace all the vacuum lines on this car. Went got all the parts and installed to find out that this car runs like brand new! Better than the day I got it that is for sure. Now for the front brakes which should be a breeze! Any tips? Gonna do the rotors also.
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Monday, April 18th, 2016 AT 2:52 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Good glad it's fixed. here is a video not of your car but it may help. make sure calipers move easily and replace the hardware it comes in a kit due to age of car.if brakes pull one way or another a caliper may be frozen if they lock up and don't release replace the hoses as they go bad as well.
https://www.2carpros.com/images/external/mqdefault.jpg
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Monday, April 18th, 2016 AT 3:29 PM
Tiny
BONEMAN 69
  • MEMBER
  • 6 POSTS
Thanks! I will check it out.
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Monday, April 18th, 2016 AT 3:52 PM

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