jseklund

Ok, Here's a recap:

1. Compression on cylinder 4 is 175 PSI.
2. I have swapped the coil packs 2X with different cylinders and the misfire stays on cylinder 4.
3. I have installed a brand new spark plug on cylinder #6
4. I have swapped the wiring on the power output stages. I didn't remove the stages, just re-routed the wires so that I could plug them into the oppostie POS.
5. I have swapped the fuel injectors on #4 & #5.
6. I have checked for vacuum leaks and did find 1, but the problem didn't go away.

The idle is very rough, shakes the car, and is consistent. The RPMS don't hunt really, but they do seem to settle in a little low. I've seen as low as 680 RPM while idling after maybe 16-20 minutes.

I have tried the idle adjustment in Vag-Com and it really doesn't help.

Last night I swapped the two O2 sensors before the cat. I was going to pull one out of my car, but Audi changed the electrical connectors. In swapping the O2's, I got a sort of strange result. At first, the car seemed better. It still shook, but the misfires went down dramatically. After about 20 minutes of idling, it misfired on cylinder #4 one time. Car idles like **** though, and is still misfiring.

Before the O2 swap, bank 1 O2 Control read 3% or so and Bank 2 read 13-14% or so. After, both were constantly hunting between -4% and +4%. I didn't expect this change????

Didn't have time yet for an ECM swap.

jseklund

Alright, another update...any ideas are greatly appreciated.

I was going to pull the ECU from my car and put it in my mom's tonight - but I didn't have a 8 mm socket, so the last screw that's behind the box to open the top was inaccessable for the time being - I am thinking of trying this.

I idled the car forever, ran through vag-com on almost everything and was just looking for clues. Then I took it for a spin and tested for fault codes.

When the car is idling, it's rough as hell. When I give it gas, it is as smooth as butter. Seems to get smooth around 950-1000 RPM.

The only thing, for the moment, that stood out to me was the V readings on the individual cylinders - bank 1 had V all below 6V, say 3.8-5.X. Bank 2 had V all above 6V - say 8.X-9.X on each cylinder. Checked this vs. my car and EVERY cylinder on my car is around 3.85 give or take. In other words, for some reason, the V to each coil is high. I think this is an effect rather than a cause, but not sure.....

Checking for codes - I now have 2 codes.

18265 - Load Signal Error Message from ECU

18256 - Please Check DTC memory of engine controller

The engine controller doesn't have any fault codes and these two messages are in the transmission and ABS modules.

I just did a quick search, and it seems that at least the first code points to the MAF???

I installed my MAF on the car and nothing really changed....so I'm wondering if I should check the wiring...

Oh yeah, and the Vag-Com shows the MAF reading about 7-8 g/s while warming up, but then it steadily drops to about 5.6 g/s at idle. This seems to be within spec to me...but I don't know much about this...

Any other thoughts or ideas would be greatly appreciated....thanks.

audinutt

Have you tried starting and running with the maf unplugged? If the idle is smooth it's either a vacuum leak or a maf issue.

jseklund

Ok,
Tried some stuff again - retested some things.

I unplugged the MAF, made no real difference. I put my MAF on my mom's car, no difference. It seems that the MAF is reading 5.5-6.5 g/s at idle and this is the same with both MAFs.

I made a boost pressure tester using the directions from AWE's website. I put the tester on the Y-pipe and tried to regulate to 7.5 PSI. My regulator sucks and doesn't do too well at such low pressure, so the thing kept blowing off the Y-Pipe. I heard NO air going anywhere. If I put my ear to the Y-pipe I heard the noise of liquid bubbling. This was more pronunced if I got under the car and it seems that the oil pan was getting pressure??? Not sure what this means, if it's bad, or if it's normal - so I just stopped. But I am pretty certain there are no boost leaks.

I held propane up to every hose, gasket, etc. I could and nothing changed in the idle.

I am pretty certain there is no air leak at this point...don't know how else to look other than a smoke machine, which I'm not sure how to connect to the car???

I disconnected both O2 sensors. When I did this, none of the cylinders misfired except for the one giving me a problem. Cylinder 4 shot up to 48 misfires and none of the others gave a single misfire.

I have to believe that if it was a vacuum leak, I'd at least get SOME kind of misfire on the entire bank, right?

With such a consistent misfire on just one cylinder, can it really be anything other than something related to that cylinder only???

My thoughts at this point are - I've eliminated the spark plug possibility, and the coil packs, and the POS. I swapped the injector with #5, but I'm wondering if I screwed that up - I pulled the 2 injectors, and decided I should replace all the lower o-rings while I was there - so I ordered them and the injectors sat for a day. I'm wondering if I thought I swapped them and didn't...I will retest tomorrow to be sure.

I also unplugged the battery to reset the ECU...and upon restarting, I believe the bank went from running lean to running rich...but it looks like it returned back to running lean. I'm not good with the lambda values, etc. - so I hope I'm not misreading them. At one point I was getting something like -20% on bank 2.

This car idles at about 680, while mine idles around 720.

My thinking is, it has to be something just on that cylinder. So, what's left? Camshaft, stuck lifters, possibly the injector. This is a new head...so I don't see how the camshaft would have a problem that I wouldn't have noticed when putting it on. I also got 175 PSI on this cylinder for compression...so I don't think it's valves or lifters...

Oh, and one last thing - when I did the boost pressure test, after I stopped and put the car back together, I started it and got a TON of white/very lightly blue smoke outta the exhause.

Any thoughts are appreciated here guys....I thought this would be a simple fix and it's been weeks and I can't figure it out....

jseklund

OK,
So this is still driving me bonkers. I am confident that it is not plugs, coil packs, or injectors - as they've all been swapped from cylinder 4 at least 2X each at this point. I am also confident that the vacuum hoses, intake manifold, boost lines, etc. are not leaking as I've checked them all thoroughly, used about a full can of propane looking for leaks, and pressurized the boost system with fair success.

I checked the resistance on each fuel injector while I had the rail out and they were all 14.5-14.6.

I tested the combi valves and they are working.

I am working on trying to get a fuel pressure tester and vacuum tester to test the lines some more, but I feel this is most likely a waste at this point.

So, I'm looking for possibilities, running the engine and listening, trying to think up something. I take the car for a spin and notice water all over the driveway. Not coolant, just water. It's most likely from the A/C, but not 100% sure.

I then start paying attention to a tapping noise that I thought was the fuel pump, which got louder after I pulled the car back in the driveway from my spin, and a bulb went off...could I be looking at the wrong side of the engine?

Could this be an exhaust leak? The tapping sounds like it is coming from the passenger's side, while the misfire is on the driver's side - so I'm not sure what to think there.

What do you gentleman think? Could an exhaust leak cause rough idle, a tapping noise, and a slight misfire on just 1 cylinder?

If the answer is yes, I sure hope it's not the intake manifold. I torqued the nuts to the head, and got the turbo bolts on pretty good...but if it's not right it is a nightmare....I'm hoping it's past the turbo and before the cat..maybe the flex pipe?

Also, the car is definately running rich on the LTFT. Both banks are slightly rich, but Bank 1 is reading -1.8 and 0.8 and bank 2 is reading -2.8 and -2.3. This is MUCH more stable than what I had previously, and the lambda sensors are showing a similar trend that is much closer to what it should be.

Mackiemd3

Probably sounds dumb my dipstick had a bad seal due to the plastic piece being broken and having a bad seal leaking in air. Fixed that and the idle smoothed out and no more issues.

Matti M

Hi,
Did you ever find out what was wrong in that Audi? I have exactly same problem with my 2005 A6 C5 2,4 V6.