cparke

My multiplicative fuel trims (A4 V6 30V) seem to always be on the rise these days! Using VAG-COM/VCDS measuring block 32, my idle/additive trims remain consistently at low normal levels, multiplicative just keep increasing negative! Bank 1 is always much worse than bank 2 also, although everything is always on the negative side. Currently, I have -15.6% on bank 1 and -7.8% on bank 2 (both are multiplicative).

Here's a summary of everything I've now done with the car so far to try to address this problem, each unsuccessful:

1) Full tune-up: fuel filter, coil, wires, spark plugs.
2) New OEM Gas cap changed
3) MAF changed
4) Vacuum lines changed
5) Engine coolant temp. sensor changed
6) Fuel injectors swapped between banks, and 1 new fuel injector installed on the more troubled bank (bank 1) too. No change in the pattern.

My short-list of remaining things which might resolve this too rich problem (oh joy!), not sure what order to go next:
- Fuel pressure regulator
- Camshaft position sensor G40
- Spark plug gap (shouldn't be bad because it is new & professionally installled)
- Spark plug wires (shouldn't be bad because it is new & professionally installled)
- Compression test & possibly valve/valve gaskets
- Oxygen sensor.
- Something else?

The basic symptoms are, following a computer reset, multiplicative fuel trims continually become more rich each day, while additive trims remain normal. Bank 1 is always more rich than bank 2, usually by a factor of 3:1 to 2:1. Both trims do rise however. Fault codes are thrown eventually.

Please help me find this problem! This has been going on for much too long already (3-4 months), and I really need to put this problem behind me!

Nate (ETKA+Scumbag)

FPR would have been one of the first parts I replaced along with the vac lines.

cparke

MAF was the first part to change without knowing the future.

The fact that the idle trims are normal, and the fact that bank 1 is the only bank actually out of spec. is what doesn't make sense to me for FPR to be the culprit. Any thoughts on that? (the only weak explanation I have is that fuel travels through the rail first across bank 1 and then to bank 2, maybe the excess pressure on bank 2 is less as a result).

Ok, I appreciate your opinion very much, I think FPR is what should do next. I know the current FPR doesn't leak fuel with the engine running and its vacuum line disconnected (and I know there is vacuum in the vacuum line), but it still could be bad, right?

Nate (ETKA+Scumbag)

..... If the vac line isn't hooked up, how do you expect the FPR to work correctly?

cparke

If fuel comes out of the FPR where the vac line goes, you know FPR's diaphram is blown.

I didn't get any fuel coming out, though of course I didn't run the car like that for more than a few seconds.

Nate (ETKA+Scumbag)

Ah, okay. That makes sense now.

Hillbilly

I've seen wierder things happen.

cparke

and wouldn't the fuel pressure regulator pressurize for the cleared bank?