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Discussion Starter #1
I've been sorting through a host of issues associated with a used 05 V8. So far I've done everything from timing belt to new transmission valve body. I think I'm finally getting the major stuff out of the way, but I'm still struggling with a hesitation and idle issue...

When I first start the car (05 V8 with about 111,000 miles, air suspension), it idles rough. Once it's warmed up, it seems to settle down a bit, though you can still feel the tremor at lights and when stopped. When you accelerate, there is a distinct hesitation. If you mash the pedal, it goes like hell. If you push on it easy, it all but dies until you give it enough to go. I recently cleared up some vacuum problems, and the VCDS now shows no engine faults. So my question is, are these symptoms of needing a tune-up (plugs, coils, etc)? Could it be a programming reset issue, where I need to re-program the throttle body (I've already don't he throttle reset with key on, push pedal, etc)? Or am I way off target and it could be something altogether different?

Any suggestions?

Thanks
 

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I wonder if this is MAF related. Full throttle uses less MAF data as I understand it, it will run rich and pour in the fuel. I ask because I don't know (anyone???) can you clean the MAF sensor?? When truck is cold, motor will need different mixture of fuel than when warm, so this too seems to fit dirty or failing MAF sensor.

Plugs also stand out like a sore thumb, especially if never changed, might make the above more sensitive.
 

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Discussion Starter #5
No bookmark here. Ordered it this afternoon. For $12 it's worth a shot, given that it says it helps with hesitation and rough idling. I'll update after the use. Though if anyone has any other suggestions, I'm open to multiple services while I'm under the hood.

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Discussion Starter #6
I removed the MAF sensors and cleaned them over the weekend. They looked very clean to begin with. I guess I didn't know what I was expecting, but I cleaned them anyway. The wires all looked good, etc. After reinstalling, I cleared any fault codes and started it up. Unfortunately, it still idled rough and had a throttle lag when starting out. It didn't initially throw another CEL, but I don't have high hopes that this will remain the case.

I'm open to any other suggestions on the problem. Throttle body reset via VAGCOM?
 

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Sounds like a vacuum leak to me. I'd spray carb and choke cleaner on the areas surrounding the intake manifold and all of the vacuum lines when the engine is running. If the idle goes up, a leak is in the area.

I doubt it's the coils and plugs as they would most likely exhibit issues at wide open throttle.

Entirely possible that a TPS is going. I may have missed it, but any faults with VCDS scan?
 

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Discussion Starter #8
I cleared the faults when I cleaned the MAF sensors, but I was getting System Too Lean in both banks 1 and 2. There were a total of 4 faults, but all dealt with the lean system. I forget the codes off the top of my head. I'm guessing they'll come back once I drive more than just around the block. I'll try the carb cleaner trick to check for leaks. All the hoses and fittings "look" good, but it's entirely possible that there's a leak there somewhere. Thanks.
 

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Def if it's running lean, I'd bet on an intake leak somewhere. I doubt that the O2 sensor is going bad, but a possibility.
 

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Discussion Starter #10
Could an intake leak cause the throttle lag and rough idle, or just the system lean codes? Just wondering if I have 2 distinctly different problems or if they are related.
 
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