RossD Reader
July 28, 2009 8:44 a.m.

I think I've figured out my own Check Engine Light coming on and off seemingly at random. I did have it check and my indy Audi mech, and he said there was nothing wrong with my O2 sensor or the cats. The CEL stayed off for a while and I realized I was only going to BP gas stations. I was also only getting the highest octane available and it didnt have ethanol in it. I am not sure if its BP gas or if its the lack of ethanol or the combination but since I've been staying away from MotoMart gas stations and sticking to BP and non-ethanol high octane gasoline the CEL hasn't come back yet. Anyone else notice this at all? Any other crappy gas stations or any other good gas stations? (This is for my '00 Audi A6 2.7T Quattro.)

Rusty_Rabbit84 HalfDork
July 28, 2009 8:51 a.m.

what codes is it thowing on?

Paul_VR6 Reader
July 28, 2009 9:05 a.m.

2.7t's throw cels for a small cross breeze. Scan it, but don't be surprised when it comes back with all sorts of random stuff that doesn't make sense. I had a similar situation with by B5 S4 which started like this (random cel for misfires) and it eventually turned into a larger problem (massive misfires) that was one of the ignition modules going bad.

RossD Reader
July 28, 2009 10:15 a.m.

I believe it was the O2 sensor(s), but my mech said that the O2 and cats were fine when he tested it and just cleared it for me. Then it came and went seemingly at random. It was off for weeks until I went to MotoMart for some gas and it came back on. I noticed that I was only going to BP gas stations so I've stopped going anywhere else and it hasnt been back since (another couple of weeks). Maybe the ethanol or crappy gas mixed with good gas would throw a code at the O2 sensors and would trip and clear when the crap would be under a certain mixture with the good gas. Just seeing if anyone else noticed this happening too?

Paul_VR6 Reader
July 28, 2009 10:17 a.m.

You'll get O2 bank efficiency codes until the misfires are bad enough to cause a cel. Never had it happen with different kinds of gas, but entirely possible. You can check it with a vag-com watching the blocks for misfires and see if its all banks or just one.

RossD Reader
July 28, 2009 11:32 a.m.

Thats some good to know info, thanks Paul.

Rusty_Rabbit84 HalfDork
July 28, 2009 11:36 a.m.

i have a stupid "Cat Effiency" code that keeps being thrown on, its the stupid Hi-Flo cat the last owner put on. I clear it out, hoping to drive atleast 1 drive cycle without the CEL popping back on, so i can get it smogged. No such luck. I even put an anti-fouling cap on it, like the caps for old V8 70's cars, trying to trick the o2 sensor... no such luck again...

RossD Reader
July 28, 2009 12:10 p.m.

Rabbit: Try running BP high octane w/out ethanol. That cat effiency code sounds fimilar. I cant remember for sure what the code was... Maybe it'll work...

m4ff3w Dork
July 28, 2009 12:11 p.m.

I thought a CEL was SOP for a VW?

Rusty_Rabbit84 HalfDork
July 28, 2009 12:30 p.m.

ya im thinking the cat is problem and i will need to get a stock one welded back on, unless my company could write some code to be flashed on my car to turn it off...

you could also get a VAG COM code reader for a laptop - like 5 bucks on ebay...

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=140335611254

Paul_VR6 Reader
July 28, 2009 2:58 p.m.

Make sure you're not logging little misfires causing that code. It will throw that code first when the ignition amps are bad with the 3pin coils and when the coils are going with the 4pin ones.

You'll need to log in to post.

Also on Grassroots Motorsports

Tonight on Grassroots Motorsports LIVE! Lee Grimes of Koni Shocks

11 hours ago in News

This may shock you, but suspension is arguably the most important part of going fast.

Classic Motorsports Monterey Welcome Party Welcomes 2000-Plus Gearheads

18 hours ago in Articles

Last night we threw a party, and more than 2000 people came to celebrate.

We're Back In Monterey for Car Week

1 day ago in News

And so it begins, another trip to Monterey Car Week.

Deal of the Month: Free Trackside Companion!

1 day ago in News

Ever wished you had a handy guide on how to dial in your alignment or adjust your dampers?

This Tuesday: Join Us at Track Night in America

2 days ago in News

This Tuesday we'll be running at Palm Beach International Raceway

Experience Monterey With Us

2 days ago in News

We're on our way out to Monterey, California, for car week.

Concours d’Lemons to Ruin Monterey Car Week Yet Again

2 days ago in News

What started as the anti-concours has transformed into a major event on the Monterey Car Week schedule.

Tomorrow, August 15: Join our Monterey Kickoff Cruise-In

2 days ago in News

Our Monterey welcome party is taking over all of downtown Pacific Grove.

Vintage Views: Classic Mini

5 days ago in Articles

Turn heads, have jolly good fun.

You Need This: Toyota With Rally Pedigree

5 days ago in News

Who can say no to a turbocharger and all-wheel drive?

Join Our Monterey Kickoff Cruise-In at Pacific Grove on Tuesday, August 15

5 days ago in News

Our Monterey welcome party is taking over all of downtown Pacific Grove.

You Need This: J. Geils's Maserati Sebring, Some Assembly Required

6 days ago in News

A rock star project will be auctioned off in Monterey next week.

OUR SPONSORS

Grassroots Motorsports Magazine

Subscribe Today

Also get your instant access to the digital edition of Grassroots Motorsports Magazine!

Learn More
xOTYstkNLTN48FHA7nPxvFo5uxvpfV3W