98 a4 b5 2.8Q.

At idle or with RPM held constant, the needle appears to fluctuate by up to 150RPM from its assumed position. It doesn't matter if I'm in gear or not, the needle won't stay put. In hopes of getting the issue resolved, I've performed the following,

1. Cleaned MAF w/ MAF cleaner
2. Replaced air filter
3. Added Seafoam to fuel tank, vacuum line (smoke show), and crank. Drove for about 130mi and changed the oil.
3. Replaced spark plugs w/ NGK iridiums (didn't know jack about gaps so I just threw them in as is. The plugs end with part# QUP, instead of the usual KUB.
4. Cleaned throttle body (Major PITA... had carbon built-up inside, managed to get it 90% cleaned)
5. Replaced coil-pack (bought it used)

Unfortunately my efforts were in vain since none of the above resolved the issue. I'm now starting to question if I have a vacuum leak, if so, how do I check for it. May be a faulty MAF or coil-pack?

Please advise. Thanks

 

Well the NGK's come preg gaped so you do not have to worry. but i had the same problem on mine and what solved it for me was i cleaned the tube on the back of valve coverers that go into the intake be carful they are fragile and can break easy.

 

I don't know where it's at as there are quite a few hoses in the back. Can you post a picture?

 

are the plugs single node? if not i'd take them out and check them. you might need to run seafoam through the vacuum system

 

im guessing if you were around your vacuum lines, you would have checked for leaks as well. i was gonna say to replace it...

 

I put in all new vacuum lines on my 30v a few weeks ago and the fluctuating idle was one of three fixes I got from the job.

 

I'd replace the vacuum lines if I knew which one's were it. Firstly, there's the thin tubes on top of the vacuum plate. I don't know what they do but do seem old and torn-ish. Then below the plate are the thicker tubes, one of which I know is the vacuum line (7-shaped). I ran seafoam through it already.

My plugs have 4 nodes. The old plugs had 1. Nothing changed as far as idle is concerned. Can someone elaborate which lines I need to replace (a pix maybe)?

 

Replace all the lines to/from the solenoid panel. Do them one at a time so you don't mix up any connections. Www.siliconehose.com has the 3.5mm ID hose you need for $.60/ft.

 

CCA4 did this. here's his thread
https://www.audiforums.com/forum/sho...d.php?t=148482

 

Nice pix. Thanks. Some of the hoses above are in different locations to mine, or at least there are less of them. I'll give this mod a shot and report back.

P.S: Another day another Seafoam-through-vacuum-line treatment. I also re-cleaned the throttle body so it's now super clean. The darn CEL is back, but I'm hoping it would go away soon.