Well, so short of changing the ECM and reflashing, I read that if you disconnect the two harnesses connecting it all the adaptation values are erased (though not the DTC's). I'm thinking maybe because the change over valve broke the adaptation values got way out of whack and because it was driven that way for so long it will be hard to get back on the straight and narrow.

So I did that. The ECM is unfortunately under a security bracket so you have to dremel out a slot to torque open with a flathead. Took 3 arms (1 to hold the screwdriver down and turn it, one to hold the ECM, and one to clamp a vice grip on the head of the screwdriver for added torque. They loctite that thing pretty severely). Thank you a4mods.com (http://www.a4mods.com/index.php?page...tml&category=1)

I'm gonna sew her back up and drive around for a bit tonight and see if there's any change at all. Hopefully I didn't hose myself somehow.

Still open to other suggestions. But good luck Stephen with the heads. It's a brave job and try to remember any gotcha's in case I have to delve there myself!

BTW what is the OFFICIAL audi repair manual? ElsaWin? Bentley Publishers? Something different?

Thanks!

1940: ECM under the security bracket with the two sealed bolts toward the top.
1943: One of the dremeled bolts.
1945: ECM freed!

 

The piston being shiny could be an indicator of coolant getting in there. Water creates steam when burned which breaks off carbon, which is why you see honda guys spraying water into thier vacuum lines. It does work, but its a dangerous method.

Flashing the ECM with a Revo tune (or whoever) won't fix anything. (at least to my knowledge) You can try swapping it without another member's ECM if you can get someone to lend you theirs, or you can get a used one from a junk yard if the numbers match. However if the ECM is the problem and this is becoming a common problem, a used ECM might not work either.

 

Oh and the official audi repair manual is ELSA WEB, you can't access it. The closest thing to ELSA is Bentley publishers.

 

My thoughts.

Seems to be temp related..I believe you mentioned startup is rough? (Coolant system under pressure could cause seepage into cylinder when the car is off cooling down.)

Happens during low fuel consumption 5 - 6th gear...ie highway driving (fuel / air ratio at optimum...add a small H2O leak...bad combustiom...missfire)

Shinny piston. this points H2O as well..

You also had a recent valve replacement? Did this missfire happen before the work?

my thoughts

I'm guessing you have a small coolant leak.

 

auditech79: Well, coolant being in there would be a very bad thing. How can I confirm this? How do I diagnosis this? I didn't see any puddling as you can see from the pic. And I never really noticed coolant dissappearing though I did add coolant once back in November. The low coolant light didn't come on, but I saw it a little low and so added it. The severe cylinder 4 misfiring didn't happen until about a month later December time frame. Before that it was very intermittent where as now it is far far more consistent.

I do have ElsaWin actually, it must be a cracked version or something as I got it on ebay. It's not linked into the main system, all the data is held locally so I won't get any updates. I think I'm going to get the Bentley manual though as I think I'm missing some crucial stuff with my version of Elsa...we'll see.

mlwaterbug: Hope the head removal went well. As far as symptoms here are the patterns I've been able to recognize.

1) On a cold start the misfiring is worse and more prevelant in different gears and can /sometimes/ be seen at idle.

2) During the first 5 min of driving or so, misfiring can be seen in 3rd and 4th gear during acceleration uphills. After the first 5 min it usually NEVER misfires in those gears ever again.

3) After the first 5 min of driving I am generally on the highway at this point in 5th and 6th gear. The distribution of misfires seems to center around 2200-2800rpms. Above that and below that they are much much less. So for instance, I can drive 90mph up hill in 6th gear and no misfires. Drop it to 65mph in 6th gear up hill and almost guaranteed to see them. Drop it down even lower to 40mph in 6th gear and they again become reduced.

4) If it's misfiring accelerating uphill in 6th gear at 65mph, I can down shift to 5th gear and it generally stops misfiring.

All this said, believe it or not the misfiring is getting much reduced. I don't quite understand it, but I think i can now positively confirm that the misfires are reducing. I would usually get misfires on flats and hills on the upside of 300misfires by the time of the top of the hill. Now it only gets maybe 20 or so and sometimes only 3-6...It /seems/ like it's improving so I'm going to keep driving it and see what happens. Maybe it's burning something off with the improved airflow from the changeover? I have no idea. Very frustrating and I don't know where to look next. I.e. how to even check for a coolant leak other than VERY accurately marking the level of the coolant while cold in the over flow tank.

I also checked the injectors to see if they were spitting and put them all in little beakers and video taped it and low and behold each was injecting normally. Little timed squirts from each one and the quantities seem to be consistent.

Should I do a leakdown test? How does one do a smoke test? Either of those worth doing?

Maybe, just maybe if I take the heads off, and stick a piece of dynamite in cylinder 4 and connect it to the coil ... maybe it will fire correctly. Or perhaps the whole car would make a good addition to the shooting range...but my guess, no one would be able to shoot cylinder 4...the gun would jam and misfire if aiming for cylinder 4.

 

Oh, and the valves weren't replaced best I know. The whole heads were sent out for rework in Dec of '08. The same time the engine short block was rebuilt. The misfires didn't start happening severely for at least a year. The coils were changed after that under the recall and then it was fine for another 6 mo or so and then it was like 2 episodes of a blinking CEL months a part. then in Dec of '10 it was happening WAY too much and then wouldn't stop.

 

Elsa Win is nothing like Elsa Web, the bentley is the closest thing.

This is what i would recommend, if its leaking into the chamber over time when the engine is turned off then we need to re-create/verify that. I would install a coolant pressure tester on the expansion tank (need an adapter for VW/Audi) and pump it up. Let it sit overnight and see if the pressure drops. If it loses a few PSI pull the plug on #4 and look inside to see if there is any coolant. If no coolant, its an ECM problem.

 

Ok, so I got the coolant pressure tester. I am wondering how long to wait after driving the car home to test the coolant. I don't want to do it at temperature because it will surely lose psi as it cools. What's a good time to wait?

I also called Audi of America and they did a VIN check and cannot find any ECM related anything with my car. No flashes, no bugs, no updates... I'm really nervous that if it's the ECM I'm up the creek with out a paddle.

I don't understand why it would work and then stop working. I'm wondering if possibly I have multiple bad coils and should replace them all with new ones instead of just focusing on cylinder 4? Could bad coils elsewhere cause issues?

Rob

 

Fascinating thread! I was just logging in to update my own thread with misfire problems in cylinders 4,5,6 when I saw this. I also had a lot of misfires especially in cylinder 5, especially in cold weather, and especially at engine startup. I was also losing coolant over time very gradually, although it got worse over time, too.

Long story short, and $3600 later, I had my cylinder head 4,5,6 replaced due to it being warped. Had it xrayed and no crack. It was top side leakage, the water was getting on the top side somehow.

I hope very much that my CEL stays off, because it was virtualy always on for years.

I would be very interested in joining a class action lawsuit, because clearly this head was misshapen from the factory and it's only over time that the metal fatigued enough that the warp was big enough to cause water getting into the cylinder.

Thank you Auditek for the confirmation. Glad to know I am not the only one.

This 3.0L has been a lemon. Mine is a 2005.

 

Been super busy, sorry bout that. Did you check it with the pressure tester yet?

If you had multiple bad coils it would barely run and there would be misfires all over the board. It either coolant getting in the cylinder or an ECM issue. Remember, shiny piston bad.

P.S. Im actually doing a set of headgaskets on my buddies old 89 4runner 3.0L which are known for warped heads and the same problem. Took both heads off and two of the pistons were shiny on the passenger's side, head was warped by .06" (a lot) He was going thru a half gallon of coolant a month though LOL!
Why is it always a 3.0L? Chit should be banned to use that size engine hahaha.