Rick Snyder

OK,

Here's the deal. My S4 is in the shop with an unknow misfire problem. The mechanics are baffled and have no idea what the problem is. Maybe you can help me/then.

A week and a half ago, right after my close call on Rabbit Ears pass in CO, I noticed that my check engine light was on. I quickly pulled over and checked a few things. Everything seemed fine, so I read the owners manual. It described a few possible problems, and then stated that if the car seemed to be ok, to just drive at "reduced speeds" and bring it in as soon as possible. I did, and the VAG tool said it was a single misfire in a single cylinder. The Audi tech said everything else checked out, so drive normal. So I did.

Well, this weekend, coming through Eisenhower tunnel on the way home from skiing, the check engine light came on again. Well, twice in a week is a little unusual...it never came on in my Avant in almost two years. So, I brough it in yesterday morning, and they found the same cylinder had misfired again. This time I told them to keep it and figure out what was wrong.

So, they still have the car, and now they can get it to misfire regularly. With the VAG tool attached, they can drive down the road, and after accelerating to 3500-4000 RPM and then letting off the gas, as the car coasts below 3000 RPM, the tool registers misfires that now chain through all the cylinders. They have no idea what is causing it or why. AND, after calling Audi in Michigan, the one guy who knows these engines the best in NA, is snowmobiling in the UP for the next 14 days. D'ough!!!

OK, so has ANYONE else experienced anything like this? At first I though it might be the O2 sensor or engine management software being effected at altitude, but now that they can get it to happen regularly, I'm not sure. They've given me a loaner to use in the meantime...a 97' A4 1.8T automatic...which makes me miss the S4 even more....and to top it all off, now I'm waiting for the S4 Avant.... UGH, what a week.

Oh well, just thought I would throw this out and see if anyone else has had this happen.

Thanks in advance,
Rick
Sick 00' S4
Awaiting 01' S4 Avant......still waiting.....

mm

Bad gas?

Silver

Did you remap the ecu?

MattS4

I live at 9000 ft and haven't noticed any misfires or had the MI light come on after the first week of having the car. During the first week, I did have an O2 sensor go bad but since it was replaced, I haven't had any problems at all. I'll try to replicate the accelerating and coasting and post results.

matt

Rick Snyder

nt

Mike

Just a thought .... aren't you the 2nd owner?.... could this be why the 1st owner didn't keep it?

MattS4

However, on the gas thread...I have had a couple bad tanks of gas since moving up here a year ago. Had to have our Cherokee and Toyota's tank drained. Turns out it's a well known problem at this station, and the locals (including us now) all avoid it like the plague.

matt

ErikR

Coastdown makes the injectors cut off. In fact any lift throttle with the clutch engaged will do this. So it shouldn't actually even be firing when it is coasting. Some designs do a dry cyl. fire to clean the plugs, but Audi has never mentioned this. Even if they did, there should be no gas to burn.

You may have a clogged/broken open injectors. That would be one reason you get the mil. light. The fuel just gets dumped out the exhaust and the second 02 sensor picks up the Hc's.

Rick Snyder

nt