I have a 2000 Audi A6 with a 2.7 (150,000 miles) which has recently began to run pretty rough (enough that car shakes at idle). It does not kill and only smokes a little at startup after sitting for hours although the exhaust does have a rich smell to it all the time. It only bringing up one code. P0300 Random Multiple misfire. It was brought to a import mechanic which did test the ignition and said it was good. He also checked the fuel system and replaced an injector and filter which has not fixed the problem. I have been doing a little research on this site. Seems as though the MAF is a common problem on these cars but don't see them causing the problem that I have. I also want to do a pressure check on the intake but am not sure how to go about doing this.
Any ideas on where to start with this one?
< Message edited by WowA6Cool -- 1/11/2008 7:53:47 AM >
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Joined: 9/8/2006 From: Holland MI Status: offline
Misfires tells me it could be bad plugs or coils. The mechanic should have picked up on that. I suppose the MAF could make it run rich. Let us know what you find out.
Are you on your OEM turbos? That's a lot of miles if you are, and good to know for the rest of us 2.7T owners.
It's a random misfire though. If it were specific coils wouldn't it specify a specific cylinder misfiring? I recently purchased the car so have no idea if it's the original turbos or not as well as any other maintenance done to the car.
You need to do a cylinder balance test to see if its really on multiple cylinder or not. This can be accomplished by checking value blocks 14,15,16 for misfires or unpluging injectors with the engine running to see if it misfires worse or no change. That will help identify what cylinders are misfiring to isolate the cause. You can unplug the maf to see if it is causing the rough idle. If the idle smooths out with the maf unplugged then its a maf issue. Also check for vacuum leaks.
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Joined: 4/25/2006 From: Tacoma, WA Status: offline
Unplug the MAF & see if it runs better, if so, then it's the MAF.
If not, I would replace the CTS.
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It can also be the ignition control modules. Had the same thing happening to me and ended up replacing those since I had just changed the coil packs and sparkplugs.
We had it happen (running rough at startup, cylinder missfire) on our A6 2.8. The dealer did and injector cleaning (perhaps the MAF got cleaned too, but I doubt it) and it has been fine since.
I unpluged the MAF and it actually ran a little worse so I gurss that rules that out.
I checked all over for vacuumn leaks and found none even while spraying carb cleaner all over.
By disconnecting ignition coils I determined cylinders 2 and 5 (center cylinders 1 each bank) to be missing. I tried swapping coils and spark plugs with a "good" cylinder but found the miss to remain at 2 and 5.
I then checked the injectors which also ssem to have a good pulse and identical ohm readings.
A little bit of oil seems to be building up in the cylinders but I have never seen a little oil keep a car from running on those cylinders. Plus like I said earlier in the forum, there is no blue smoke but it does have a rich raw fuel smell.
oh, compression on these two cylinders measures 130.
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Joined: 4/25/2006 From: Tacoma, WA Status: offline
Read & follow post #7......
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I am not particularily sure whether this is the case for 2.7T, but when I used to work on my old V8s, intake runner for a cylinder is usually coupled with another cylinder on the opposite site. So if you develop a leak on one side, it also fouls up the other side as well. Since you are misfiring on 2 and 5, I suggest you dig a bit more into vacuum leak possibility. It could be the intake gasket to the head, and it is letting air into both no.2 and no.5 cylinders.
As for the oil, if the car misfires, it tends to build up black tar like substance. It is basically semi-combusted gas residue. Are you sure that what you are seeing is oil build up, not just uncombusted gas residue? If it is oil, you might have a bigger problem on hand.
Are the ignition control modules located on the air box? Are these available from most car part stores?
Yes they are on the airbox. Usually you can get them at parts stores but theyll be like 100 bucks each. I wanna say swap them from side to side but im not sure if that will help with diagnois at all. What was the compression on the other cylinders? The balance is what really matters. If you want you can leave the coil connected with the spark plug out. Make sure its laying on the valvecover so its grounded. If you have spark, that pretty much rules out the ignition control module. Just for the hell of it I would try swapping injectors, but itd be odd for two to go out at the same time.
tried that with the injectors already. Actually replased one of them. no change. I did not check compression to the other cylinders. That may be my next objective.
just had the same thing happen to me ... 550$ at the dealer to replace ignition control module ?? the codes came up missfire and i replaced all the plugs and coilpacks no change so i gave up bc of lack of time and the dealer replaced the ICM and now she runs fine
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2002 a6 2.7t / GIAC / REMUS / AWE-Tuning s-flo intake / bailey's DVs / vast stage 3 tip chip /vast piggies / obx manifolds / k04's and rs4 ecu platform to come soon!
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