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Discussion Starter · #1 ·
My wife's stock '02 AWP has been thowing missfire and lean codes. 6 times in 5000 miles, 3 times in the last 1000. We've taken it to the stealership since day one and the last few times we've taken it in for the cel, they've replaced the front O2 sensor, reprogrammed the ECU at the 60,000 mile service ( cel was on), then this last time they replace the coolant temp sensor and cleaned and decarbed the injectors and valves. And the light came on 150 miles later

The car has a total of 61787 miles. I think it's about time to invest in a vag-com and Bentley CD and charge it to the dealer
 

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Re: Multiple missfire & lean code- ideas? (Hybrid VW)

There may be a reflash disk available for that car, also has it had a MAF sensor yet? Have they pressurized the intake system to check for air leaks? How about coils, are they all "L" coils? Any, or all of these things could cause those faults, almost certainly not an o2 sensor or coolant temp sender.
 

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Re: Multiple missfire & lean code- ideas? (90LX)

Coil packs??? have they looked at the coil packs??? as previously mentioned, do a fuel pressure test. maybe the fuel filter is clogged (this should have been changed at the 40k service. let's hope they did it), or a fuel line is blocked. the fuel pump could be bad, or the fuel pump sock inside the tank could be clogged. Reprogram the ECU!!!!???? there are plenty of things to check before doing that. people at the stealerships....That would have been the last thing id try.




Modified by stirfriedx9 at 7:00 PM 9-10-2005
 

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Discussion Starter · #6 ·
Re: Multiple missfire & lean code- ideas? (stirfriedx9)

They repalced the coil packs a while ago, I'll check which ones they are when she gets home. I don't have a way to check the fuel pressure, but I do have another 3 bar fpr laying around, and can probably hunt down a guage to borrow. I really hate to stereotype mechanics, but some of the ones at this place are pretty incredible- they tried lifing the car once without having the lift positioned properly, gouging the rocker panels and at the 60,000 mile service they did the seat heater recall and didn't bolt the drivers' seat back in properly!!
And 90LX, hurry up and get your tin can fixed and go back to your Rustang forums
I don't care if you DO turn an 8 sekkond 1320
 

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Re: Multiple missfire & lean code- ideas? (Hybrid VW)

Check injectors or injector wiring harness, not a common failure but this does happen and will cause lean mis fires. Intermitant fuel pump/pressure issues could cause the same problems.
 

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Re: Multiple missfire & lean code- ideas? (4thvw)

Take it back to the stealership and tell those dumbasses to do a fuel pressure test. Any mechanic should be able to do this basic service for you. It is not hard. if they can't do it, go somewhere else, or tell them to give you a new car!!! And, I agree with the above comment.
 

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Re: Multiple missfire & lean code- ideas? (stirfriedx9)

Also check the suction-jet pump, if that thing gets clogged (which they do ALL the time), it can cause all kinds of issues. I highly doubt it's a fuel pressure issue. A car with 60k miles on it probably has at least a couple of air leaks in the crankcase breather system. Probably needs a MAF sensor as well.
 

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Re: Multiple missfire & lean code- ideas? (Hybrid VW)

yes, but not if it is dirty. i dirty MAf sensor typically won't throw a code. you can get a dirty MAF when tiny particles of water or oil (from an over oiled KNN filter) coat the MAF.
 

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Discussion Starter · #12 ·
Re: Multiple missfire & lean code- ideas? (Hugh Gordon)

Well, it does have the "L" coils, and the MAF looked clean (paper filter), but I didn't have time to pull the screens off to get a closer look. Plugs had a little "powder" on the electrodes, but other than that looked fine. Also cleaned the IAT sensor. Anything else, as far as I can think, will require a vag-com or other equipment that I don't have at my disposal right now.
 

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Re: Multiple missfire & lean code- ideas? (Hybrid VW)

Quote, originally posted by Hybrid VW »
And 90LX, hurry up and get your tin can fixed and go back to your Rustang forums
I don't care if you DO turn an 8 sekkond 1320

Watch it, I'll keep your drive flange tool for another 2 years!
 

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Re: Multiple missfire & lean code- ideas? (dtm337)

Quote, originally posted by dtm337 »
mass air...

yeah... you could try giving it an alcohol bath. aren't some mafs covered under some recall too?
 

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Re: Multiple missfire & lean code- ideas? (ReverendHorton)

Most MAF sensors have an extended warranty now up to 70k. I say most because I know for sure that it applies to the older cars (99-02?), but I was informed recently that it didn't apply to newer ones. I'm really not sure on the split in years on that. I can't believe the dealer hasn't put a MAF sensor on a car with a too lean code......
 

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Discussion Starter · #18 ·
Re: Multiple missfire & lean code- ideas? (Hugh Gordon)

I talked to the service manager yesterday, and he pulled the "run lower octane fuel" bit on me. He tried to say that with day to day driving, if you don't drive the car hard, the slower burning fuel (91 octane) leaves carbon deposits in the combustion chamber that cause misfires
Of course, after sending him the following email, I just realized how much more assinine that theory is since if anything, higher octane would leave more deposits at high rpm since it doesn't have as much time to burn..... Anyway, here's the email that I sent him, we'll see what his response is:
After thinking about the codes our car had when we had a friend scan it (misfires on all four cylinders and a lean condition), I don't believe that fuel octane is the issue. I don't know for certain that the most recent CEL is for the same issue, but the same issue has popped up a few times in the past, so I'm assuming that it's the same one right now. My reasons are as follows:
1) The factory designed the engine to take advantage of fuel with an octane rating of at least 91. This is shown by the rather high (9.3:1) compression ratio when used with some form of forced induction. I sure this was done to improve off boost drivability.
2) I don't think it is even possible to build an engine that is so sensitive to octane that you need low octane for day to day driving in traffic to keep the combustion chambers clean, and can't benefit from higher octane fuel.
3) Misfires won't cause a lean condition, but a lean condition can contribute to misfires. If there are carbon deposits creating hot spots in the combustion chambers, thereby causing pre-ignition, it can't cause the O2 sensors to read lean. They will either read read rich (due to improperly burned or unburned fuel), or have a reading consistant with the mixture that the ECU asked for. In order for the O2 sensors to read lean, there has to be more air or less fuel in the cylinder than the ECU requested. Carbon deposits can't introduce more air into the cylinder and can't reject fuel (I suppose deposits on the injector side of the valve could stop fuel from making it into the CC, but I would certainly be disappointed in your attempt at cleaning the valves if that was the case since the CEL came on so soon afterward).
4) This leads me to believe that the root of the problem is either in the air measuring sensors (MAF of MAP sensors), in the fuel system (fuel pressure regulator or something impeding the flow), or in the ECU tuning (since the problem has been more frequent since the ECU was re-flashed at or around the 60,000 mile service).
5) It is also possible, I believe, that the parameters for the CEL may simply be too stringent. These are misfires unnoticable to the driver, and there's no doubt that many cars in the past have had these issues, we just weren't aware of them.

I believe that VW did a god job designing this engine, but may have come up short on the electronics side of things, as evidenced by faulty MAF's and coil packs. The engine itself has been proven numerous times to be capable of making in excess of 500 hp without changing anything inside the longblock, so I would hope it's able to run properly for more than 62,000 miles in stock form.

Thanks for your attention and consideration on this matter.
Kelly Farrington

BTW, my friend's website is http://www.EFI101.com, and I believe he is holding a class in Renton in October.
 

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Re: Multiple missfire & lean code- ideas? (Hybrid VW)

Good luck man... you are on the right track with some of those theories but I think if you saw some logs of what the mass air sensor was actually reading it might change some of your ideas.
Most likely, the car is not actually running lean. The MAF, going bad, is reading more air than is actually coming in. The ECU looks at that figure and thinks you are lean when really you probably have extra fuel getting dumped in to accomodate the extra air that isn't actually there in the first place

That is the point where I usually unplug the MAF and run without it until I can afford a new one... because you are probably getting horrible mileage from those screwy readings (I have seen a 5mpg gain just from unplugging a bad MAF)
 

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Discussion Starter · #20 ·
Re: Multiple missfire & lean code- ideas? (ReverendHorton)

Quote, originally posted by ReverendHorton »
Most likely, the car is not actually running lean. The MAF, going bad, is reading more air than is actually coming in. The ECU looks at that figure and thinks you are lean when really you probably have extra fuel getting dumped in to accomodate the extra air that isn't actually there in the first place


But AFAIK (which isn't a while lot about the factory ecu), the ecu uses the O2 sensors to read if the car is running rich or lean, and in the example you gave, that would make the car run rich, as evidenced by your milage
 
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