Digit@lex

My car (1999.5 1.8T) has been unstable at idle lately. I managed to get the car to stall at least 5 out of 10 times driving around today when I clutched in at a stop light. The only codes that the car logged were 16684, 16686, 16888 (basically Random misfires in certain cylinders).

I know that the car was running rough before it even logged those codes and began stalling. I could tell that the rpms began dipping more and more randomly.

I swapped back to stock plugs and the car still seemed rough. The CEL only went on once the entire time. When I'm driving, everything is fine. I am still getting the expected boost so I don't believe there is a vacuum leak.

One thing I did observe:

I unplugged the MAF connector as a final test and started the car (saw this from an older post). The idle was still rough. Do you guys think my MAF has bitten the dust since there was no difference in ? I haven't seen any codes related to it though.

Thanks for any help.

JAFO

do a search on "ignition amp".

Digit@lex

Thanks but I already swapped out the ignition amp. No success there.

Audi R4R

Not that it makes a huge difference by any means, but maybe try unplugging the ECU for 10 min. How many miles on the car? performance mods?

Idle is most likely a electrical issue if the car runs fine except for idle issues. The MAF is a good place to start, but I've blown the MAF a few times and I noticed I had more boost issues than idle issues.

I have a brand new A4 1998 1.8T MAF if you're interested. Just send me an e-mail with an offer.

Cheers!,

Steve

Digit@lex

I have a T-28. :-)

I did some more debugging and it seemed to be the 1.5 bar chip. I popped in the 1.3 bar chip again and the idle became rock solid. I'll try the 1.5 chip again in a few weeks and see if it reappears.

For the MAF do you know if the 98 and 99.5 MAFs are the same? I could always use a spare. ;-)

See you in a few weeks!

StevenH

I was having terrible idle on cold startups until recently. The only way I could keep the car running on cold startup was to hold the car at 2k rpms until the motor warmed up a bit. The ecu had tons of misfire codes and it showed there was a bad 02 sensor. This morning I finally changed the 02 sensor and the first time I started it up cold it didn't idel perfectly but the car would hold itself at 1.2krpm until it warmed up, it no longer fluctuated and sputtered between 400 and 1k rpm and misfired everywhere. Our symptoms sound pretty different but maybe its a sign that your 02 sensor is about to go... I would try borrowing someone elses before spending $150 on a new one but it may be worth a try.

StevenH

Check your bpv. Out of boredom one time I ran my BPV as a BOV and while the car would run like crap whenever I was off throttle or idling it would run perfectly and hold full boost as long as I was on the gas and some pressure was keeping the thing closed. The car stalled about 4 times when I drove my car to the end of the block and turned around.

Audi R4R

Sorry 'bout that! If you're running a T-28 properly,... you won't have use for an OEM MAF anyways. That's how I blew things up as a temporary fix. If you try to max the power on the T-28, the MAF (OEM) is destined to fail. I don't want to sell you the MAF, but if you really want it, I've held on to it for too long now. I bought 2 and blew one and my mechanic found a solution. But now with the stand alone ems, I don't need a MAF anymore. YEAH! I have a chance to idle.

His solution was a Ford MAF from a Mustang. It is great for the high end and maximizing performance. But drivability really suffers. It never idled consistently.

You'll have to check up regarding the MAF for the 98 versus the 99.5 difference if any. I don't know the parts except for the 97 & 98 similarities,... I can bring the MAF with me on the plane if you want it! So you can see it in person and we can save shipping, etc.

Btw,... mind telling me what else is in the A4?

Cheers!

Steve

Digit@lex

APR snub
AWE DTS
Neuspeed Bilsteins / Neuspeed Sport Springs
Milltek Exhaust
19mm Neuspeed Rear Sway
Neuspeed Short Shifter
EVO FMIC

I still need to upgrade the brakes and will most likely switch to H&R coilovers next year. I also have an EFK waiting to go in. I'll wait until I'm in the mood to rip my front end off again.

That's pretty much it. I'm really trying to hold off on the modding. :-)

Digit@lex

With the 1.3 bar chip back in the car, the idle is relatively smooth again. However, I still think something doesn't feel right. I could be just overly sensitive but the car seems to vibrate a bit more than normal. My initial thought is the 1.5 bar is exposing something degrading in the car.

Since I have almost 75k, I'm thinking about changing some components. The things I have in mind are:

MAF
02 sensors

I think I will order a new MAF today. I will look into the cost of 02 sensors as well. I don't mind stocking up on those parts since they need to be replaced eventually.

I really think I need to change my fuel filter too. I am looking into the Motorvac carbon cleaning solution as well. I'm keeping the car for the long haul so I will change things, even if it's a little premature.

Hmmm, I guess I'll get back underneath the car and do some more inspecting. I guess I'll start with the BPV.