00 S4 Cyl 1 Misfire At Idle Only

[B5-S4 Bi Turbo]

Hey everyone,

New to the forum and first time posting, but to start I am a Expert Level Audi Certified Tech at a dealer so no need to worry about misleading or confusing statements but I'm at a loss of options.
I have a 2000 S4 that only misfires in Cylinder 1 ONLY at idle, P0301 Cyl 1 Misfire Detected Intermittent ONLY CODE, on average 20-40 misfires per min at idle, but when cruising, WOT, or off idle all goes to 0 misfires. I have swapped in new coil packs, new OEM "pink top" fuel injectors, new intake manifold gaskets, swapped ICM's, swapped ECM's, checked mechanical timing, checked cam adjusters/tensioners, checked timing gear to cam (sometimes the "D" profile of the camshaft to cam gear can get rounded but it is flush), compression tested all cylinders 205-215 PSI, cylinder leakage test 5%, running compression test 60 psi all cylinders, vacuum gauge at idle for entire engine 20" hg and steady with no fluctuations, checked every vacuum line/hoses/check valves for leaks, fuel pressure at idle is 50PSI (specs something like 40-60 or so don't remember exact but I know its ok), swapped in new fuel pressure regulator, checked ECM harness for any chafing on bulkhead studs, checked resistance of coil connectors and fuel injector connectors, used boroscope to check for carbon - none anywhere, checked cams for worn lobes, checked lifters and valve springs. The f hose is silicone and new, the crankcase breather system is new (spider hose assembly new), tried a capacitive discharge but still no change. Car is 100% stock. I've completely run out of options, my thoughts are an extremely small burnt area of a valve or extremely slight bent valve or a sticky/notchy valve guide? Any other input/sugguestions appreciated.

[DiscoPotato]

Does the car have a ecu that was tuned by Marc at any point and time?

On a side note have you tried unplugging your maf and running in closed loop?

[S4James]

lol i got the same thing with 1 and to a lesser degree 4... load issue/poorly tuned injectors for me.

[B5-S4 Bi Turbo]

Yes I have also tried unplugging my MAF and it has no effect and no the car is 100% stock both ECU's swapped in were 100% stock as well as another tech I work with has a 00 Negaro Blue S4. Anything you can think of at this point will be checked lol

[protocol_droid]

Since you've replaced icms, coil packs, plugs..... it sounds like a bad injector with crappy spray. Happened to my stage 3 as well. Swapped in new injectors (Dave from EPL recommended this) from an EPL kit and vois la, no more problems.

[DiscoPotato]

Injector most likely.. Have you tried ATF in the oil system to rule out a sticky/clogged lifter?

[B5-S4 Bi Turbo]

All 6 injectors are brand new less than 100 miles ago with OEM "pink top" injectors. I did add a can of BG MOA Oil additive and have driven it every day to work and back about 60 miles a day probably 4-500 miles so far and still no improvement.

[evounder]

Does it eel like there's a miss or is it just the diagnostics telling you?

[S4James]

there have been cases where the misfire was actually occurring on the opposite bank. might want to check out cylinder 4

[protocol_droid]

even though you can "check" the check valves, they can still leak and cause issues as well.

[B5-S4 Bi Turbo]

I've clamped off and checked, re checked, and re checked everything again I promise even both of my shop foremans went through the entire process and are stumped. Yes you can actually feel the misfire occuring it's not just telling me that it's missing it actually is stumbling/bouncing around at idle but still just in cyl 1. I've decided since all other options have been exhausted (no pun intended), I'm gonna yank the head off and take it apart. Hopefully I find something that will make sense but if not I'll at least be able to clean everything up and lap all the valves. What exactly did you mean "S4 James" by your statement?

[goohead]

Valve guides or seals maybe

I had same issue rebuild heads problem gone. May or may not be your issue

[goohead]

Also 205-215 comp test seems high but could be your gauge or you do have some carbon build up that you didnt see, did ur 5% leak down come from the rings?

[B5-S4 Bi Turbo]

I pulled the head off tonight after work. Everything looks beautiful and very clean for 108K miles, virtually no carbon on the pistons. I checked the passengers side turbo since it's just hanging out in the engine bay still bolted up - no back and forth play but it does move around in all the other directions. Most likely Monday I'm gonna take apart the head on my bench and see what I find or don't find. I'll keep all posted.

[vagra4nt]

Update?

[JETSPEED333]

your compression results seem high to me no? ...i thought spec was aprx 180..... ounds like youve covered most the bases though...how about checking for wiring shorts to the engine sensors?...maybe even a new engine overlay is nessesary....sorry to hear about all this, lol

[jasman19]

Doing the leak down test is the better way to determine if you have a burnt valve, head gasket issue, or the rings are shot. I personally prefer doing this test to a compression test because the leak down test rules out any of the above being a problem. I think you've pretty much covered all the items that would cause a misfire on the one cylinder. Only thing I can think of is a cracked head or leaking head gasket that is allowing coolant into the cylinder. My first thought, based on your first post, was an injector issue, but you said you replaced it already right?

[JackalS4]

First thing, I don't think you actually mentioned changing your spark plugs - or gapping them - unless I missed it or you just forgot to mention? I would assume you did this a long time ago though by the sounds of it...

Reason I bring this up is I had this issue and it ended up being one plug from NGK not having been gapped correctly (they're supposed to come pre-gapped apparently and this was the first time my mechanic had seen one not gapped correctly from the factory).

Just wanted to make sure you covered that base.