Hey, all. My AAN is experiencing fuel cutoff, trying to track down the culprit. Fairly certain it's an ECU fuel cutoff- the car will be pulling hard under boost just fine and then quit and throw you forward like it hit a wall. After a second or so it will start puilling really hard again as if nothing happened, and then hit the wall again.
It doesn't feel like the spark is blowing out- I've expereiced that as well and that is a much softer failure mode. WIth a spark problem the car will start sputtering and lose power under boost, but this is this really sharp, sudden failure that almost feels like you hit something.
On my mitsubishi we call it "fuel cut" and it usually happens because the airflow signal from the MAF is going over some "danger limit" in the computer so the ECU shuts off the fuel to save the motor. Sometimes that's because there's a big boost leak, sometimes it's because there's a problem in the MAF, sometimes it's just a turbo upgrade that has the system worried. So that's what I think is going on here on my 1995 S6.
I used to have a huge boost leak in the Audi and the fuel would cut off at around 5000 rpm, but now I've fixed that, and it *was* running much better until one of the coils went bad. (This car has the coil-on-plug mod that removes the POS circuits)
I replaced the offending coil, and now I'm getting random fuel cutoff at seemingly random high and low RPMs to the point where I can't use the car. I can't for the life of me figure out what the coil would have to do with it, but I tried swapping in a different new coil and the problem persisted. Coincidence, maybe?
I also noticed that it runs better when it first starts. The problems with the fuel cutoff don't really start before I've taken the car a few miles and it's warmed up.
I also cleaned the MAF thoroughly with MAF spray cleaner, and that seemed to help, but it's still not really drivable.
So what do you guys say is failing here? And how can I verify the broken part before spending a bunch of money on a replacement?
Thanks!
It doesn't feel like the spark is blowing out- I've expereiced that as well and that is a much softer failure mode. WIth a spark problem the car will start sputtering and lose power under boost, but this is this really sharp, sudden failure that almost feels like you hit something.
On my mitsubishi we call it "fuel cut" and it usually happens because the airflow signal from the MAF is going over some "danger limit" in the computer so the ECU shuts off the fuel to save the motor. Sometimes that's because there's a big boost leak, sometimes it's because there's a problem in the MAF, sometimes it's just a turbo upgrade that has the system worried. So that's what I think is going on here on my 1995 S6.
I used to have a huge boost leak in the Audi and the fuel would cut off at around 5000 rpm, but now I've fixed that, and it *was* running much better until one of the coils went bad. (This car has the coil-on-plug mod that removes the POS circuits)
I replaced the offending coil, and now I'm getting random fuel cutoff at seemingly random high and low RPMs to the point where I can't use the car. I can't for the life of me figure out what the coil would have to do with it, but I tried swapping in a different new coil and the problem persisted. Coincidence, maybe?
I also noticed that it runs better when it first starts. The problems with the fuel cutoff don't really start before I've taken the car a few miles and it's warmed up.
I also cleaned the MAF thoroughly with MAF spray cleaner, and that seemed to help, but it's still not really drivable.
So what do you guys say is failing here? And how can I verify the broken part before spending a bunch of money on a replacement?
Thanks!
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