AKS4

OK, I STFA and from what I gather it sounds like it could be my fuel pump going out based on my symptoms, but would like to know if these also point to anything else.

A run down of whats happened, I have been having a periodic rough idle at start, that would go away once warmed up. Friday evening while tooling around town, I noticed a weird vibration/hesitation upon giving it gas. it happened once, shut off then restarted after a while (shopping) drove fine till about an hour or so later and yet again same thing, I eased off the throttle and eased back on and it was fine. Scanned the car when I got home and the only codes were: 16826 - EVAP Emission control; Small leak | 16805 - Warm up Catalyst; Bank one; Below threshold | 17539 - Oxygen Sensor B2 S1; Internal resistance too high, intermittent.

I knew of the EVAP (part on order) and didnt think a bad O2 would cause the bucking I was experiencing (very similar to a bad MAF) No smoke, no burning, no smells. I Decided to clear them and see what popped back up and being intermittant might be a fluke. Drove into town yesterday fine, then on the way home every stop light was acting the same.. bucking, pretty badly. Bad enough I went back to my bros whom I am house sitting and took his car. Will scan over lunch today for any new codes.

Does this sound like a bad fuel pump? with the bucking under more than half throttle. Or could the warm up on the cat be a portion? Bad 02? anything else to consider?

TIA for any info.

S4AVT

mileage is high enough to fail near the future..

I've ordered mine already...

AKS4

Wanna come by and check it out? its sitting over at my brothers place. Second set of Audi ears would be helpful.

S4AVT

what we can do is, we can log it with my ecu-x and check te injector duty cycle...

it will mostly tell..

AKS4

If nothing else the logging will tell me if its Fuel related.

AKS4

Any other things one might run down with these symptoms?

stickyS4

2nd on the fuel filter...I'd try that first

AKS4

Soooo, I scanned the car again when I got home. Multiple misfires detected, cylinders 3 and 6. Park came over, he told me to log blocks 15 & 16, sure enough cylinder 6 was misfiring , 3 not so much. even at idle it was "OK" (~15 per vag sample cycle) Took it around the block and HOLY MOLY, ~250 misfires during a VAG sample cycle...... within a couple blocks... went back home, per Parks recommendation I started to swap cyl 4-6 plugs and cyl 5-6 coils. I didnt need to go too far however, upon removing coilpac on cyl 6 the chamber had a "soot" look to it so knew something was up. As I began removing the spark plug found it was LESS than HAND tightened.. W teee Eff? After checking the plug to make sure not damaged, I tightened it back down, cleared the codes and started her up. Vag was reporting NO misfires. Buttoned up the engine and took around the block, VAG was reporting no misfires yet again... Problem solved.

However at my mileage I should still invest in fuel filter. And now need to fix/short the coolant level sensor seeing as one wire broke off and the coolant warning is blinking at me.

Anyway, just an update. Thanks again Park.