intermittent random misfire on 5 cylinders when engine is hot
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1st Gear
Joined: Jun 2011
Posts: 2
intermittent random misfire on 5 cylinders when engine is hot
please help i have a 2005 audi a6 4.2 with 85000 miles. car is fine when first started in the am, full power runs great but rpm meter flucuates when under low acceleration (bounces up and down, u can feel the car surging). after car has been driven 5 to 10 miles and has reached normal operating temperature it misfires pretty bad everytime i stop. my cel flashes and goes solid. power loss and poor acceleration, new oem plugs and coil packs. Had car scanned and came back p300, p301, p302, p305, p306, p307. after car cools down and sits for a few hours it runs fine. had new coolant temp sensor installed too. clueless audi suggested fuel injectors but was not 100% sure (why would 5 injectors malfunction at the exact same time everytime). any ideas anyone,
3rd Gear
Joined: Dec 2008
Posts: 1,941
From: IL
So all the codes are related to cyl misfiring... and you ruled out spark plugs, coils and CTS.
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* First thing to check (and even replace) is the fuel regulator's vacuum hose. Forget the "clothed" type - it is the worst type of hose you can waste your money on.
I would assume the car is not that old to be in need of a new a fuel filter, but you never know. And since you're at it, check every single little vacuum hose and if not sure of its condition, just replace it. Can always pry one end out and look at the core rubber's condition. You don't want to see any cracks or tears in the rubber. Believe me, the clothed type doesn't last. It's like instead of rubber they just wrapped in clothing a tube of paper...
- (Try also adding some fuel injector cleaner in your next tank -Techron, etc)
* If the vacuum's not the root cause, then the second step I would take is to check the timing, just to make sure that's not the problem.
* Did they rule out the Catalytic converters?
----
* First thing to check (and even replace) is the fuel regulator's vacuum hose. Forget the "clothed" type - it is the worst type of hose you can waste your money on.
I would assume the car is not that old to be in need of a new a fuel filter, but you never know. And since you're at it, check every single little vacuum hose and if not sure of its condition, just replace it. Can always pry one end out and look at the core rubber's condition. You don't want to see any cracks or tears in the rubber. Believe me, the clothed type doesn't last. It's like instead of rubber they just wrapped in clothing a tube of paper...
- (Try also adding some fuel injector cleaner in your next tank -Techron, etc)
* If the vacuum's not the root cause, then the second step I would take is to check the timing, just to make sure that's not the problem.
* Did they rule out the Catalytic converters?
Thread Starter
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1st Gear
Joined: Jun 2011
Posts: 2
audi checked the timing and said it was fine. its crazy because it only misfires when car is hot or has been driven for a while. cylinders 12567 misfire at the same time, u can physically feel the car shake. cat was fine i needto check my vacuum lines. could it be a fuel pressure regulator problem or icm because it only happens when car is hot.
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