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What's causing misfire at idle?

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my95tsi

20+ Year Contributor
926
0
Dec 6, 2002
Chicago, Illinois
Ok i fixed a butt load of problems on my car recently but i still ahve the same re-occuring problem that i've had for the past 3 months. My car will start up just fine in the morning and drive fine all day but when it start her up after she's already warm the car idles at like 200-300 and tries and stay alive but about 50% of the time it dies. I have to rev it up to keep it from dying, but when it's reved up the car still misfires and pops just at a higher rpm. I don't know if it's a misfire or something else. It does it everytime my car is started when its warmed up. I have no CEL so it makes it even harder to diagnose. I had a problem on the higway just recently that when i gave it wot in 5th the car would cut out like2-3 times really quickly. I checked the plugs and they are fine, i have to bpr7es plugs but the prongs were almost all white b/c they are cold. However my gap was way too much so i fixed the gap and it cured my 5th gear problem. My wires are less than 2 years old and they are fine. They are excel 8mm thundersports. I was told that it sounds like a bad fuel pump problem but i can't check it b/c i can't hear my fuel pump even when it is running. I'm running out of ideas. I drive my car all the time and i drive it to and from school (500 miles) all the time with no problems except for when i need to restart her. If anybody has any suggestions it would be greatly appreciated. :thumb:
 
There are several things that can cause this. Here are some of the obvious things.
Check your spark plugs, take them out look at them.. are the electrodes intact, they melting, seated properly... they may be too hot causing detonation. (hot spots in your head causing the fuel to explode before the plug does) Look at your boots... they worn? cracking pluged in all the way. What kind of plugs are you using? Are they gapped right.
Check your TPS, not sure where it is on a turbo, mine is on my throttle body. go to the auto store get a can of electrical contact cleaner, spray it out plug it in. Also do the same for your idle air control valve. Feel free to PM if you have questions. (I will respond much quicker than on the thread) best of luck
 
Plugs and wires were check thoroughly and are fine. The electrodes are intact, the plugs look perfect except for the white spots. Here's my question, why would it do this only at a warm startup? It doesn't effect anything while driving and the car pulls the same, so if it was plugs and wires wouldn't it effect everything not just random idling issues.
 
Ok just for the hell of it i rechecked the plugs and wires and they all seem good. The plugs are fine and they don't smell like gas so that rules out a bad dinjector, but then again i'm not having a problem starting her while warm only keeping her alive. I have noticed lately however that my vacuum at idle is at 16hg when it used to be a constant 18hg for the life i have owned the car. Is this a sign of a boost leak or somehting else?
 
Spray carburator cleaner on hoses and gaskets around the TB and intake area after car is warmed, if you have a vacuum leak the rpm should change a little if you sprayed at the right place. Perform a complete boost leak test and make sure the biss and TB shaft seals are not leaking. Measure the resistance of TPS, IPS and ISC as per service manual, make sure they are adjusted properly. Good luck.
 
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