Rough idle
11-09-2012, 06:58 PM
#1
Staging Lane
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Location: Aurora, IL
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Rough idle 98 Trans am with 110k.
Car has a rough idle on start up ONLY when it is cold outside. I am talking 35 degrees or below. During the summer it runs perfectly fine.
I've already done a tune up. Plugs, wires, fuel filter. I also checked the air filter and it's clean. I also cleaned the MAF and IAC. Nothing fixed it.
It will do this until the car fully warms up.
Here is a video I took from my phone.
http://youtu.be/Dw_FjR6P3Xk
Car has a rough idle on start up ONLY when it is cold outside. I am talking 35 degrees or below. During the summer it runs perfectly fine.
I've already done a tune up. Plugs, wires, fuel filter. I also checked the air filter and it's clean. I also cleaned the MAF and IAC. Nothing fixed it.
It will do this until the car fully warms up.
Here is a video I took from my phone.
http://youtu.be/Dw_FjR6P3Xk
11-09-2012, 09:00 PM
#3
ThirdgenTa,
Next time the engine is cold......unplug your MAF and THEN start it up. If it does the exact same thing your MAF is probably failed. And NO...not all PCM's will throw a code for a bad MAF.
What I think is happening is...The MAF runs the engine when its cold, after it warms up to 122*F (I think thats the magic number) the 02 sensors take over to run the engine and it smooths out.
Try that and see what happens.......hopefully thats it. Easy fix.
.
Next time the engine is cold......unplug your MAF and THEN start it up. If it does the exact same thing your MAF is probably failed. And NO...not all PCM's will throw a code for a bad MAF.
What I think is happening is...The MAF runs the engine when its cold, after it warms up to 122*F (I think thats the magic number) the 02 sensors take over to run the engine and it smooths out.
Try that and see what happens.......hopefully thats it. Easy fix.
.
11-24-2012, 08:43 PM
#6
wonder if youve got a bad intake manifold gasket, causing
it to run rough/misfire and when its cold because the gasket
is shrunk and distorted..when its warm it swells and seals.
had this exact same thing on a customers truck with the intake
manifold gasket...fixed it.
it to run rough/misfire and when its cold because the gasket
is shrunk and distorted..when its warm it swells and seals.
had this exact same thing on a customers truck with the intake
manifold gasket...fixed it.
11-24-2012, 09:24 PM
#7
Teching In
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i had new gasket put on and had a smoke machine on it to see if intake was cracked it wasn't. i replace ect sensor all 02 sensors, tps sensor, maf sensor, new spark plugs and wires. and checked with vacumm gauge and that was fine also. also changed the pcv valve, i get a po300 code to
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11-25-2012, 03:53 AM
#8
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Vacuum leak someplace cold...as the engine runs a little and gets warmed up things change ALOT. The PCM starts running off the 02 sensors, engine smooths out. CHECK YOUR FUEL TRIMS...then post back.
