Audi A4, AEB, misfire.... out of ideas, looking for opinions what to do next

NYSpeed Automotive
1

Was coming home from the dump this am in the wife’s Audi. Shift to 5th, it starts studdering bad, like a misfire. So I let off, it goes away, as soon as I get back on it misfiring again, and now the CEL starts flasing at me. I coast home a mile and now it wont start.

Code is a cyl 1 misfire.

Im immediately thinking coil pack since I think they are original and the car has like 155k. Cyl 1 coil pack is cracked, who knows if thats the real issue. So I pull the plugs and cyl 1 plug the fn center electrode is GONE. The plugs look to all be in really bad shape (guess I should have checked/replaced them sooner).

So I ran down and got new plugs and it started right up , but soon after started knocking pretty bad, and the misfire came back.

Cyl 1 is very wet, it looks like oil (im guessing fuel would have evap’d by now).

I pressure tested the coolant system and it seems to hold 20psi just fine.

Could this be a combination of a bad coil, maybee the electrode still in the cyl (I dont have a bore scope handy), and possibly a bad head gasket, causing oil to leak into cyl 1?

THoughts?

Dan

2

AEB should have the external ICM on the airbox? rotate coils and see if the missfire follows it. if not, i’d suspect the ignition control module. they’re as problematic as coils. if you have oil on the plug, i would also do a leakdown and see if something isn’t broke as far as hard parts.

3

Yes, it has the ICM on the airbox. As far as I can tell, from a couple online sources the ICM is ok when I check it with a DMM (diode check).

I did do a compression check ( I dont have a leakdown tester) and the oily cylinder was the best at 180psi. They were 180 / 130 / 150 / 160. I should double check #2.

The odd thing is after I put new plugs in the motor idled normal and quiet for a few secs, then it started stubling/misfiring and knocking really loud. Im assuming that the knocking Im hearing is from the misfire, but its so scarry loud that it sounds like something mechanical.

I also drained the oil and didnt find any glitter.

Dan

4

the oily part could be from a leaky valve cover gasket… it loves to well up in the plug holes, that is until you remove the plug, letting the oil fall into the cylinder.

Other than that, replacing the cracked coilpack on cyl 1 sounds like what you need to do…

5

swap coils cyl to cyl, and see if the missfire follows the #1 coil. and the ICM’s can come and go… they bench test/static test “okay” but under load they fail. if you do replace the ICM, put some heat transfer grease between it and the heat sink on the airbox so it’s got a fighting chance.

6

I would still be guessing the coilpack has gone on cyl 1.
doing the plugs wouldnt save that

7

Ya, I need to find some good parts to swap to see if its just ignition related or if that horrid knock is mechanical.

Searching around now.

EDIT: I dont recall ever hearing a horrid knock like this from just one cyl misfiring. My old VR GTI used to misfire all the time, and I dont recall the rediculous knock (but it has been a couple years).

Dan

8

keep the bad part in the mix, see if you can reproduce the missfire in another cylinder to verify a faulty component.

9

so after a bunch of Fn around, and more or less just putting it all back together, it finally started again. It was idiling super rough, but managed to idle long enough for the cel to start flashing again, with multiple misfires. I reved it up a couple of times, and after a min or so it ran perfect. I shut it off and started it right back up… idles mint, no misfires, no horrid knocking. In fact it idles better than it did before (used to idle a couple hundred rpm high). I let it warm up and rechecked the compression for fun and got 190/193/197/205.

So im wondering if that piece of the #1 plug electrode was causing preignition and hence the misfire and knock and now its “gone”.

The scary part here is where did it go? I estimate it was a pretty long piece. It seems to have broken pretty far up into the plug, almost 3/4".

I need a bore scope yesterday.

Dan

10

http://nyspeed.com/forums/showthread.php?t=72939

11

ya… little far from Macedon to Jason’s shop.

I bought a cheap fiber optic one, will be here wed.

Dan

12

Got the bore scope today. I couldnt see any damage from the plug electrode in the cylinder, nor any pieces of it. It looked no different than any of the other cyls.

I also pulled the O2 sensor out and took a look at the turbine blades. They too look perfect.

Drove it around for about 45 min. I had one misfire in cyl 4 at about the 3min mark. From then on it ran mint. I drove it as varied as I could also. WOT in every gear under different loads and rpms etc. Was perfect, nothing odd. Makes full boost etc.

Its like nothing ever happened.

13

i know there were clearly other problems… but maybe you just had some bad gas working through, on top of the other stuff?

or… it’s an Audi; it was just menstruating, and now you’re good for another 25 days.

14

well it def had one problem with the cyl 1 plug completely losing its electrode.

Im still freaked out I cant find any evidience of it falling out … anywhere.

15

Well, it lasted 3 days. On my way home from the store today (man i gota stop driving this thing home from stores on sundays) I got the flashing CEL and cyls 3 and 4 misfire this time. I was able to limp it home after a few mins of fn around, but now its knocking at idle witout any codes since clearing them.

I think the spark is still an issue. The spark seems super weak watching it while turning hte motor over. Its just a super tiny blue spark.

Im wondering if I should just replace everything, coils and ICM with new AEB stuff, or swap to the ATW coils and bypass the ICM. Its about 200 bux cheaper to do the swap, but then the car wont be stock (not that I really care I guess).

I need to make a decision here soon… carpooling blows.

Dan

16

Got the new coils and plugs today. Put them in… its still knocking, shit.

So I let it warm up, same, go for like a 2mile drive… no more knock, but I get one misfire in cyl 4 (I should mention I also changed the oil. I had put some “heavier” than normal oil in last week when I checked the oil as it was all I had that day. Im guessing that was the source of the knock).

Clear the cyl4 misfire, drive again… few mins later get two misfires in 2 and 4. So may as well check the MAF… as Im cleaning it ever so carefully with a qtip and some alcohol part of the filiment at the outlet side (that has the little dark line on it, maybee 3/32" wide) basically breaks free. UGH. Its just hanging on for dear life at the sensor side. Sweet.

17

I have a brand new-never used MAF for an AEB… pm me if you’re interested, i’ll let it go for $125

18

Ok, so new MAF didnt fix anything either. I wasnt sure it would, but I had to replace it since it was broken anyway. Here is waht I have done so far…

Two sunday’s ago I lose a complete electrode from CYL1 spark plug (like completely, right back to the resistor) and CYL1 code is set (duh). This happened while running WOT shifting between 4th and 5th. Car is not chipped, completely stock.

I can never find the missing electrode, my only guess is it somehow got thru the valves and out through the wastegate.

Compression on all cyls is still good, something like 193/196/200/200.

I bore scope all the cyls I cant find any damage or remnants of the missing electrode. Also looked at the turbine blades through the O2 sensor hole, no damage there or sign of the electrode there or on top of the cat.

Put 4 new plugs in it runs for a few sec then starts knocking real bad, running rough etc.

I pull all of the coils off and check all of the electrical connections, and then spark while cranking the motor over. I have spark on all 4. Everything thing seems to test ok so far.

So I say F it put it all back together, get it started…sorta. After a few mins it starts to idle ok again and the knock goes away. Go for a drive, no misfires. I drove it every which way I could. Different loads, different gears, rpms etc etc. No misfires. I should note at this time that I had drained the oil to see if it was full of glitter and I only had straight 30wt to put back in ( ya I know I should have went to the store to get the right oil). There was no glitter.

This lasts 3 days until once again I am driving it and it starts to misfire.

I limp it home and its back to its old crap again. Misfires ahoy etc and now its knocking… sorta bad.
I order 4 new coil packs and a new ignition module and 4 new Bosch plugs (the parts store didnt have the right ones). I also get the right 0W40 oil and a new filter.

Get those all in. Car fires right up and idles no issues, except the knock. I let the car warm up and go for a like 4mi drive. I get back to the house, the knock is gone. Must have been a lifter issue. I take it back out and get a misfire. Clear it. Drive about 5 more mins, get two more misfires. ugh.

I pull the MAF out to clean it, since Im running out of ideas. As Im cleaning it with a Q tip and some alcohol a little piece of the filament fn falls off… ya, broken. UGH. I just hardly touched it… I used to clean other MAFs all the time, never had this issue.

So I take the car back out with the MAF unplugged, running in limp mode. Drive it around like this for a while, no misfires. So maybee it was the MAF all along.

Pick up a new MAF from the dealer , get it in. Its no better. Still misfiring etc. The knock is still gone, luckily. Its like nothing has changed.

Im running out of ideas. I havent checked the fuel pressure yet. Otherwise any thoughts on what to do/check next??

Also, what besides MAF and O2 does the car ignore in limp mode? Im guessing if I go back out tonight with the MAF unplugged it wont misfire anymore.

THoughts?

Thanks!

Dan

19

ICM. do it.

http://www.ecstuning.com/Audi-B5_A4-Quattro-1.8T/Engine/Ignition/ES1723/

I think this because a failing ICM could cause sporadic misfiring, and occasionally work fine without you really changing anything… with no definitive pattern.

I think a fuel pressure problem would be more consistent.

OT.
looks like ECS tuning has wheel bearing kits for b5’s for $45 each now, nice. :slight_smile:

20

Ya, I replaced the ICM when I did the coils and plugs. I did some more work last night. I forgot to update this post… here:

I unplugged the MAF and drove around in limp mode. For a while it was fine. Then I did some long pulls in third… from low rpm and got it to miss. It wasnt enough to throw any new codes, but enough that it bogged for a mile or so until it finally would go hard again.

Ok. So I got a fuel press gauge jimmied up on the windshield so I can watch while driving. The idle pressure with and without the vac line is right on spec. The pressure tracks boost perfectly too. So Im wondering if the stumbling I was having in limp mode was just from being in limp mode, since the map might not be perfect.

I then took a couple hour break and then hooked the new MAF back up and cleared the code before I started the car. (last night I put the new MAF in but didnt clear the code, and just started driving and had the misfires right away).

So with the MAF back in, no CEL and full boost I drove around for over an hour. I did all sorts of different gear pulls, boost levels, rpms etc. THis time not a single misfire, stumble anything. The fuel pressure tracked the 8psi just as well as 4psi. Its perfect. Of course this is the same thing I thought a week ago.

I also drove the car to work and home today with no issues as well.

So Im cautiously optomistic that its fixed now. Only time will tell I guess.

EDIT: I ordered a new O2 sensor too for kicks. The one in there looks to be original, just like everything else on this car… well before recently.

Dan