Out of ideas - Lean Mix
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AudiWorld Member
Joined: Sep 2007
Posts: 21
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Out of ideas - Lean Mix
Ok, I've run out of ideas, and I'm hoping you guys can help.
I keep getting the p1128 code for lean mixture/MAF/O2/Vacuum leak. I checked the plugs, and yup, its lean - white.
I have already replaced the MAF (twice), and running without it plugged in doesnt change the performance. I replaced both O2 sensors, and checked fuel pressure. I get 45psi @ idle, and about 55 @ 4000 revs. Seems right to me. I pulled the whole fuel rail out, and activated each injector, and they all seem to spray a nice even fan pattern, and seem equal. I also replaced the fuel filter. I have gone through and replaced all the small vacuum lines that were even a little suspect.
Under slow driving conditions, the car is ok, but at full throttle, it is awful. If I try and do a WOT run in 2nd gear, I cant get above about 5k revs before it starts missing badly. If I back off to about 1/4 throttle, it seems to richen up, and will pull better than at full throttle. Basically to pass another car, I have to feather the throttle to get any decent power out of it.
Does anyone have any ideas up their sleeve for me? (I dont have a VAG).
I keep getting the p1128 code for lean mixture/MAF/O2/Vacuum leak. I checked the plugs, and yup, its lean - white.
I have already replaced the MAF (twice), and running without it plugged in doesnt change the performance. I replaced both O2 sensors, and checked fuel pressure. I get 45psi @ idle, and about 55 @ 4000 revs. Seems right to me. I pulled the whole fuel rail out, and activated each injector, and they all seem to spray a nice even fan pattern, and seem equal. I also replaced the fuel filter. I have gone through and replaced all the small vacuum lines that were even a little suspect.
Under slow driving conditions, the car is ok, but at full throttle, it is awful. If I try and do a WOT run in 2nd gear, I cant get above about 5k revs before it starts missing badly. If I back off to about 1/4 throttle, it seems to richen up, and will pull better than at full throttle. Basically to pass another car, I have to feather the throttle to get any decent power out of it.
Does anyone have any ideas up their sleeve for me? (I dont have a VAG).
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Joined: Dec 2000
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Related to Johns suggestion..>>
Do a fuel pressure check. With a gauge on the lower Fuel rail nipple it should be 45-50psi, rising under boost. Trace fuel delivery back. Filter, fuel pump etc could all be culprits. We're assuming you replaced the 2 braided hoses to the FPR and the Combi valve as these are failure prone and break under the braid so it cannot be easily seen. Breaks here commonly cause lean conditions. Make sure all those hoses are attached UNDER the manifold and haven't come off any of the nipples. Another hose to check is the one at the far (passenger) side of the manifold. Often the rubber "S" shaped piece will fracture out of site and allow a direct vacuum leak...
Thread Starter
AudiWorld Member
Joined: Sep 2007
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Re: Related to Johns suggestion..>>
Yep,
So far I have done all of these things. New hoses, and fuel pressure checks out to what you said John. All of the lines underneath were cracked and leaking before I began searching for the problem, and each time I think I have it fixed, I find a new one. Still searching though.
Keep the ideas coming!
Thanks so far...
So far I have done all of these things. New hoses, and fuel pressure checks out to what you said John. All of the lines underneath were cracked and leaking before I began searching for the problem, and each time I think I have it fixed, I find a new one. Still searching though.
Keep the ideas coming!
Thanks so far...
AudiWorld Super User
Joined: May 2000
Posts: 21,112
Likes: 1
Ross-tech.com
I think <a href="http://www.ross-tech.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=VCKU0&Catego ry_Code=VAGCOM">this </a> is the least expensive option, and if you do your own maintenance will easily pay for itself.
That interface won't work for the mk2 TT if you're planning to upgrade to one anytime soon, you'd need the hex-usb which is another $100.
That interface won't work for the mk2 TT if you're planning to upgrade to one anytime soon, you'd need the hex-usb which is another $100.
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