Audi A4- Check engine lean burn

Before starting I should preface this by saying yes, yes i should have written this car off a long time ago. I have spent much more than it is worth but now it’s serious and I am not giving in. Beside my wife likes it and call the car “Helmut”.

The car is a '97 A4 with 110K and has a check engine (engine burning too lean) The garage I was using, used a VAG COM scanner and they followed the instructions after showing a “too lean” error. So, the garage recomnended and changed O2 sensors(both) , mass airflow meter (changed twice), vacuum lines checked and rechecked. The last thing he was going to but unable to do was to check was the fuel pump.

My question is after having all of these parts changed how can I know if any of the changed parts needed to be changed? It was VAG COM that recommended changing them. It seems that they just followed the recommended list with no regard to whether thy were broken or not. To me it seems a terrible way to go about fixing an engine.

It cost me an arm and a leg too

I say this because when the sun roof began opening(a bit) spontaneously in warmer weather the garage said "to replace that’s going to cost you $800. I went online

and found a fix - the switch relay contacts need to be bent upwards a hair. That was all…

Thanks to everyone for your comments and advice.


New York City

PS During this the oil cooler sprung a leak and the CAT died and had to be replaced.

PPS Happily I am booked into a Car talk recommended place this Friday and all this will be history.

PPSS The car does and always has driven as smoothly as the first day I got it.

Think of the O2 sensor as a messenger & then think of the old saying “dont shoot the messenger”

PO171 is probably the code that came up

From the factory shop manual for my 02 Hyundai Sonata.

Trouble shooting flow chart for trouble code PO171 Too lean bank 1.

  1. Faulty ignition system.

2.Faulty fuel delivery system. Low fuel pressure

3.Clogged fuel injector

4.Faulty fuel injector.

5.Vacuum leak in intake system.

6.Leak in exhaust system.

7.Faulty MAF sensor.

Number 1 makes no sense to me for a lean condition, but I did’nt right the book, the engineers at Hyundai did.

The flow chart for your Audi should read similiar, have the mechanic show it to you.

Is this a 4 or 6 cylinder & do you know the trouble code or codes?

John, you need a new shop - no question about it.

Be skeptical of the CarTalk mechanics files - they’re not as handy as those who suggest it imply. I’m not saying not to go to the new shop - just don’t assume you can let down your guard. You need to ask around among people that know for a new shop - of course, in NYC that might be hard.

Thanks for that. The latest is, they did a smoke test and found a missing clamp and a leaky hose. So maybe and it’s a big maybe it was vacuum line. Fingers crossed.

I’ll let you know when I get it back.

First thing I thought of when I read this post was a vacuum leak. Too bad more mechanics don’t use a vacuum gauge. Vacuum gauges are cheap, install quickly, and can reveal in a few seconds if a vacuum leak or other problems exist.

I also agree that you should not put all of your faith into a shop simply because it’s recommended here and also agree that shop was guessing; especially based on replacing the MAF twice incident.

I hope that’s it… on my A4 I have run lean due to vacuum hoses in the past. Also, the MAF air sensor does tend to go on the fritz. The latter is something you can test yourself if you are somewhat handy. If you search online there are lots of good tutorials on how to remove this sensor, and it can be cleaned with rubbing alcohol.