Rough Idle/Misfire

[belinko]

Ok, don't go flaming off, because I've done my search.

Car is an 01.5 AWM 1.8T 107K on the clock.

To begin with the car was running fine. During my last oil change I noticed a cracked hose for the Secondary air system (emissions). It was the 90 elbow which sits just to the left of the Coil packs and then it turns downward towards the Cat. This hose was brittle as shit. I had to crack it off to replace it. I stuck a rag in the hose to prevent any small parts falling down the pipe.

As soon as I replaced this hose, I started to get the rough idle at 800rpm.

While I was in there, I also noticed a the Air Pump hose was broken so I replaced that too (weird plastic hose with a quick connector on each side). I wasn't expecting it to fix the rough idle.

I checked the codes and I was getting a misfire on Cyl. #2 and I had two evap codes, which got dealt with.

Last night I swapped in 4 new hitachi bolt down coils and new spark plugs. F***ing thing is stil misfiring. Checked all of the hoses and pressure and everything looks good.

I'm stumped.

[kextyn]

What codes are you getting?

I had a misfire a while back on one cylinder. I replaced the spark plugs, coils, etc. The code I had was something to do with the circuit for the coil I believe. It turned out to be a broken wire just before the connector to the coil. It was idling a little rough before that and I suspected it might be missing. So I was disconnecting the coils one at a time to make sure it wasn't missing. After plugging that one back in I had a 3 cyl engine. The wire was apparently already damaged and it just completely broke when I unplugged it.

[belinko]

I have a feeling its going to be related to wiring, which sucks for me.

Could be a bad injector wire as well??????

Code was a basic misfire on Cyl. #2

[belinko]

Oh yeah!

No CEL's what so ever.

Car is running great except for the idle at 800rpm.

[belinko]

Got some Throttle Body Cleaner, took off the TB and cleaned the hell out of it. I disconnected the negative side of the battery, reset the ecu and did the throttle body adaptation.

Also picked up some injector cleaner and poured it in the tank.

Car is running considerably smoother, but a slight vibration/misfire/rough idle persists. Everything feels good at WOT and everywhere else besides 800rpm. So far I've put on roughly 35miles on the car this weekend and I'm hoping the rough idle will sort it self out.

I just got a CEL, I'll check it tomorrow. I think it might be related to the injector cleaner. If not it might help me determine the cause of the rough idle.

[a4syth]

My a4 had a very similar problem last year.. diagnosed as a third cylinder misfire.. i was told that it might be my ignition control module so i ordered one online made by bosch for 85ish and installed it real easily myself.. just 2 screws and a few minutes and it was easy to get at it as well.. car was immediately running back to normal once i put it in.. let me know if you need further help.. good luck!

P.S. the part number was 0 227 100 211 so if you google that, you should be able to find it

[Squarrl]

2001.5 don't have ignition control modules

[belinko]

Just checked the codes.

P0300 - random/multiple misfires
P0302 - misfire on Cyl #2

[belinko]

2001.5 don't have ignition control modules

^^^^^^^ Got any suggestions?

[Squarrl]

I would think a leak somewhere, since you checked everything else I would.

even though your coil packs are new try swapping them around still, you never know

[belinko]

Misfire was on cyl #2 on the old and new Coilpacks.

Since the misfire keeps occuring on Cyl. #2 I'm going to pull the injectors and swap them around. While they're out, I'll clean them with the ultrasonic cleaner as well.

It still could be a leak in a vacuum line.

[drunknmunky408]

Try your n75 valve or your MAF... I had the same issue last year.

[belinko]

^^^^^ What fixed it for you?

Already replaced the MAF.

Any way to test the N75?

[belinko]

Well,

I was looking over some things and I noticed an excess amount of dirt around the injectors, even more so around injector #2.

I'm also hearing a very high pitch leaking sound at startup. I think the injector seals are leaking.

I ordered 8 new o-rings and 4 retaining clips today. I'll probably do the install tomorrow and post back later.

I'm crossing my fingers and hoping this does the trick. If not I'll keep, keep'n on.

[maxspeed]

what makes you think a faulty n75 will cause a rough idle?

[drunknmunky408]

^^^^^ What fixed it for you?

Already replaced the MAF.

Any way to test the N75?

I first replaced the n75 first but that didnt do anything. then i went to the MAF and it was good. I literally changed everything... sparks and coils.

[belinko]

Alright, pulled the injectors tonight, they were dirty as hell. Replaced the o-rings, retaining clips and cleaned the snot out of the entire area.

Nonetheless, rough idle at 800 rpm persists.

I'm kind of thinking fuel pump now.

It seems like the car is starving itself of fuel at idle.

[matt719]

I really don't have any experienced input on the matter, but just looking at it logically, if it's the fuel pump, why would it be rough at idle and run fine at WOT? Seems like it would be just the opposite.

Sounds like it might be a disagreement between your MAF and oxygen sensors.. aka one or the other are bad or the system isn't sealed. My father has a 2001 and the only time I've seen those symptoms was when I was cleaning the throttle body and left a hose off. Maybe you could describe the symptoms more in depth? How often does it misfire? Does it do it all the time or only when cold? Etc..

[belinko]

Yeah, the fuel pump thing was a brain fart, it was late at night when I made that post.

I'm thinking its related to the PCV system.

As far as symptoms are considered: Rough idle at only 800rpm, its a slight shutter/hesitation to move forward, with a hint of misfire. Once again no CEL's. On a cold start up I have been hearing a high pitch whine/leak from the air box compartment area. In general the car is running great under WOT and everywhere else besides the low rpm band.

Attached is a picture with a valve that is circled. What is it? I think this is where the noise is coming from. I also hear and feel this valve pulsating/knocking when I hold.

I looked over my check valves; some have been recently replaced and others have not. I've been doing some reading on the PCV system and it seems that the culprit could be in there somewhere.

Any help is appreciated

[eurotecknik]

I can't say much. But logically trace the problem back to the 90 hose that you've changed because that's when you started to see problems. Check if everything is installed properly and all fluids like coolant and engine oil aren't low. Just a thought.

[errol]

i know this is an old thread.. but what was your fix?

[belinko]

Combination Valve

http://www.audigeeks.com/forums/index.php?topic=3052.0