Engine Misfire Diagnosis Help Needed
#1
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Engine Misfire Diagnosis Help Needed
Dear All,
Thanks for the recent help with issues with my new $6500 A8L. I wish for help with the following please.
Misfire: With more regularity when I start my car from cold engine at about 30-40F it will run rough and clearly misfire and shake, especially at idle in gear. On some ocurrances it seems(does) cleanup and smooth out immediately after the high idle is over, this take about 10-30 seconds. Sometimes it will be rough on start, then better after was restarted within minutes of shutdown. At other times the missfire persists the entire drive and fuel economy drops off a lot.
I have chased the problems of coils and poweroutputs on other models and cars, and started out by checking the connection to al the coils and harnesses and adding diaelectric grease to the injector and plug connections as well as the coil connections.
It would seem that the variables of this problem are not a coil, but a sensor that may affect mixture and the mixture is too rich. I will purchase a few coils (unless recall covers?) and start swapping them. I will also disconnect one coil at a time and check fore differences and repeat for injectors.
Disclaimer: NO VAG/BENTLEY or O2 sensor YET
If you have any suggestions please reply.
Thanks,
RG
PS I am in Southern WY, and when or if we ever get snow I am going to run this car wide open up more snowpacked road with the ESP on, it seems like an F1 car when you do it and I suggest everyone try!
Thanks for the recent help with issues with my new $6500 A8L. I wish for help with the following please.
Misfire: With more regularity when I start my car from cold engine at about 30-40F it will run rough and clearly misfire and shake, especially at idle in gear. On some ocurrances it seems(does) cleanup and smooth out immediately after the high idle is over, this take about 10-30 seconds. Sometimes it will be rough on start, then better after was restarted within minutes of shutdown. At other times the missfire persists the entire drive and fuel economy drops off a lot.
I have chased the problems of coils and poweroutputs on other models and cars, and started out by checking the connection to al the coils and harnesses and adding diaelectric grease to the injector and plug connections as well as the coil connections.
It would seem that the variables of this problem are not a coil, but a sensor that may affect mixture and the mixture is too rich. I will purchase a few coils (unless recall covers?) and start swapping them. I will also disconnect one coil at a time and check fore differences and repeat for injectors.
Disclaimer: NO VAG/BENTLEY or O2 sensor YET
If you have any suggestions please reply.
Thanks,
RG
PS I am in Southern WY, and when or if we ever get snow I am going to run this car wide open up more snowpacked road with the ESP on, it seems like an F1 car when you do it and I suggest everyone try!
#2
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Clarification: It is a 2004 A8L that had 140K for $6500 and I was rebated $1000 from the dealer cause they were a toyota dearler and Audi was in LA, 400 miles away.
I am looking to unload this car for about $9150.00. This is after a lot of work, and the car is or will be solid. Let me know if anyone has REAL interest.
I am looking to unload this car for about $9150.00. This is after a lot of work, and the car is or will be solid. Let me know if anyone has REAL interest.
#4
AudiWorld Super User
You really need to run diagnostics. If you are not going to purchase the interface, let us know what part of the Southern edge of the big cattle ranch you're located near (Rock Springs, Rawlins or Cheyenne etc). Maybe one of us is nearby and can meet up with you.
I have had a similar problem when the airbox (air filter element box) was not properly sealed between halves. Also, you can look for a air leak in the large hose/tube/plenum between the air box and intake manifold. Heck, the Mass Airflow Sensor could be the culprit. Again, diagnostic software and interface would really help you here.
I have had a similar problem when the airbox (air filter element box) was not properly sealed between halves. Also, you can look for a air leak in the large hose/tube/plenum between the air box and intake manifold. Heck, the Mass Airflow Sensor could be the culprit. Again, diagnostic software and interface would really help you here.
#5
AudiWorld Super User
Additionally you should check for any outstanding Campaigns and Recalls by Audi with the VIN number at
http://www.audiusa.com/us/brand/en/o...in_lookup.html
When I bought mine it needed the new coil packs and Audi happily applied the TSB for free even though it was well out of warranty.
http://www.audiusa.com/us/brand/en/o...in_lookup.html
When I bought mine it needed the new coil packs and Audi happily applied the TSB for free even though it was well out of warranty.
#6
AudiWorld Super User
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#8
AudiWorld Super User
Additionally you should check for any outstanding Campaigns and Recalls by Audi with the VIN number at
http://www.audiusa.com/us/brand/en/o...in_lookup.html
When I bought mine it needed the new coil packs and Audi happily applied the TSB for free even though it was well out of warranty.
http://www.audiusa.com/us/brand/en/o...in_lookup.html
When I bought mine it needed the new coil packs and Audi happily applied the TSB for free even though it was well out of warranty.
#9
Replace your spark plugs. DO NOT USE ANYTHING ELSE, BUT NGK plugs. There is a huge difference between NGK vs other vendors for Audi.
I replaced mine and the problem went away.
I replaced mine and the problem went away.
#10
Don't think it's coil packs...
I'm not an expert, but I'd expect coil packs to give the symptoms under load, not at idle (our TT and A6 gave those symptoms). I'd go with fouled plugs to start with.
K9
K9