Hello Audiacs -

My 2003 A4 just started doing something really ugly tonight. (Its a 1.8t front wheel drive 5-speed. I think it has an AMB motor)

I possibly gave it a little too much gas in second, at a fairly low rpm - nothing ridiculous, but the engine bogged down, almost stalled, and immediately started running VERY rough, flashed the yellow check engine light, etc. SO, I babied it back home. It sure felt like I was down to 2 cylinders..! VERY rough and very little power, too.

I've got a generic OBD2 scanner. I'm not sure if a better scanner/software would give more precise info, but this is what I got:

Stored DTC (S)

P0300 Random/multiple cylinder misfire detected
P0304 cylinder 4 misfire detected
P0303 cylinder 3 misfire detected

Pending DTC (S) Detected During Current or Last Completed Driving Cycle

P0140 Oxygen Sensor Circuit No Activity Detected (Bank 1 Sensor 2)

I searched around for the codes in the forum, but wasn't very clear on what these all meant, especially together. They all happened at once, FWIW

Any guesses where to start? Any help would be appreciated.

Thanks!

ALSO - I don't know if this might be related, BUT the car has been running fine for a few months, but I've had the little blinking red gas icon flashing for a while now. (NOT the big "low fuel" warning...) Supposedly, that has to do with the gas cap seal, but I bought a new cap - but it made no difference. I've also heard that it might be a vacuum leak somewhere causing that light to go off. I HAVE noticed that my MPGs seem a bit low. I do a lot of freeway driving, at reasonable speeds, and I am averaging about 25 MPG, which seems a BIT low (but tell me if I'm wrong about the MPGs). Another Audi guy told me that a vacuum leak of some sort might cause the computer to run the motor a bit more rich than normal, possibly affecting the MPGs. Any guesses?

 

i would lean towards a vac leak. But my first question is have you replaced your coils ever?

 

No, I haven't replaced the coils. I've had the car about 6 months, and when I first got it I did the timing belt, etc., and I think changed the plugs (the old ones seemed fine) but NOT the coils. I will take a look.

Your guess of something like a big vacuum leak is pretty likely, based on how this problem suddenly started. I will look for that, and maybe try to find/check oxygen sensors too. And price coils...

Thanks.

 

coils are farily cheap. U might even have luck if u go to the stealership and see if the recall has been done on the car. As for the vac leak inspect the check valves for corrision. The heat cycle these cars go thru with all those plastic valves is just such a pain. Also make sure all the lines under the manifold and behind the block are tight with no leaks. :: a4mods.com :: - The Premiere Audi A4 Modification Guide and Pictures Library

 

Thanks guys,

The verdict? One bad ignition coil. I checked them all (and the plugs) and swapped them all around. The computer picked up the location of the bad coil more than once. Swapped it with a new one, and everything is happy again.

Thanks for the link on vacuum leak test. I will have to give it a try, when looking to solve that remaining blinking "gas" light. I should check for possible recall items too. I had heard that the whole headlight assembly for this year qualified for a recall. Thanks again for the help!