shwndh

I just bought this car cheap because of the miles and the car runs fine but when you look at it through the VAG, you can see misfires just rolling in. I go as many as 40 at idle in one frame across all cylinders randomly. Here are the codes:

16684 Random/Multiple Cylinder Misfire Detected
16685 Cyl.1 Misfire Detected
16686 Cyl.2 Misfire Detected
16687 Cyl.3 Misfire Detected
16688 Cyl.4 Misfire Detected
16690 Cyl.6 Misfire Detected
19989 Cyl.5 Misfire Detected

The only thing that makes the misfires go away is switching from 93 octane gas to 89. With 89 I only get like 1 misfire per 3 to 4 min monitor but performance is not as good.

Even with all the misfires there's no way to detect they're happening while driving or at idle - car feels the exact same. The only way I knew they were there is because of a CEL that triggered once. I cleared to codes and switched to 89, clear (?) Makes no sense.

Before switching to 89 I fixed a vac leak to the MAF, had all plugs changed (OEM NGK's) by an indy shop, and I got all new Coil Packs (the latest version "L") installed and it was the exact same until switching to mid grade gas.

I would just stick with the 89 but I notice the performance difference and I'm not convenced that this is my problem. No one else on the B6 forum with a 3.0 is having the problem with me. Any ideas? The main things to check is Vac leaks, EGR (dont think this car has one), plugs and coils. I'm lost. Any ideas?

Bracketracer

can you cut and paste an autoscan for us to look at?

shwndh

ran it on the VAG again after I mixed the 93 with some 87 to try to get it around 91. I ended up with about 90 and the misfires were reduced to about 5 to 7per monitor. As it stayed longer on the test the reduced even more to about 3. So there's a direct corralation between the octane level and the misfires: high octane=high misfires, low octane=lower to no misfires.

Uwe@Ross-Tech.com

Measuring block 032..

These get reset to 0 when you clear fault codes, so you need to drive it some after clearing fault codes before you'll have meaningful numbers there.

-Uwe-

shwndh

with the registered software. I'm at work right now. I'll try to pull this when I get home.

But what does it look like? Is it the Lambda reading? The only other time I've seen fuel trim is in a fault code (lean or rich).

Bracketracer

<ul><li><a href="http://www.ross-tech.com/vag-com/cars/fuel-trim.html">http://www.ross-tech.com/vag-com/cars/fuel-trim.html</a</li></ul>

shwndh

Can someone tell me what kind of pressure I should be looking for at the fuel pressure regulator?