robertl

My wife was driving my 2002 A4 1.8T when it decided that it no longer wanted to respond to the gas pedal. Since then, the car will start, but then immediately stall. I listened for the fuel pump to come on when I took the ignition to the on position, and it sounded pretty normal. I don't have a vag-com, and my scan tool showed no codes or faults. Since it isn't throwing a misfire code I feel I can throw out anything with the coil packs. My current thoughts are fuel pump or fuel filter, but I'm not sure and wouldn't know how to test for this. Any ideas?

lyleswk

One vote ESS (Engine Speeed Sensor). I think the generic OBD tool won't see this as this is an VAG specific error.

edit: Link for DIY if interested.

http://www.a4mods.com/index.php?page...eedsensor.html

AudiCO

Not sure if it's the cause of your problem, but I would change the fuel filter if it has not been changed before. I have an '02 also and I was experiencing some strange issue until I changed the fuel filter within the past year; hasn't returned since.

robertl

In the article for the engine speed sensor, he states that he had an EPC light on, but I don't. Does that necessarily mean anything? I was able to do on test for fuel pressure by depressing the valve on the fuel rail while the engine was cranked and I had plenty of fuel spray. So now I'm not thinking fuel pump or filter; although I'm probably going to replace the filter anyway just cause it seems like it's about time. So the only lead I have is the engine speed sensor. Does anyone know if that would throw a code or not for sure? I'd hate to spend about $100 for nothing.

juttin

Hmm u probly did if not did u look to see if any hoses came apart? or maybe a wire to throttle or some other cable somewhere. Does your wife remember any noises or anything that she noticed about car before this happened?

lyleswk

Maybe s4master can jump in here, but I don't think that the EPC will necessarily come on with a flaky ESS. I thought about fuel supply also, but my thoughts were that a weak pump / clogged filter result in misfires since the engine is not getting the fuel the ECU is asking for.

s4master?

Tom in Seattle

It could be a problem with the key immobilizer system. Our car will randomly exibit this symptom. It starts and the rpm comes up to 1000 and then immediately dies. Up restarting it's fine. It's done this maybe half a dozen times over the last few years and so far we've not found a solution.

bboissonneault

You can test the immobilizer, by simply turning the key to ON (not running) If the illumintated key symbol on the guages goes out (no longer illuminated) then the immobilizer is fine.

Another place to check would be the throttle body adaptation. If you have a vag com cable and vcds software, it is easy. There are a million posts on the internet, including this site on how to do so. If you have an automatic, you will need to adapt the kickdown settings as well.

It could be the crank position sensor (engine speed sensor) as well. You should have stored codes if it is. EPC light is not a necessary symptom of this problem.

Finally, I would check the voltage of the battery, both running and not. You need to have 11.5 volts, not running, for everything to work right. You should have just over 14 volts, running on a decent battery. Low voltage can cause all kinds of weird stuff.

robertl

OK, I disconnected the MAF sensor electronically and started the car. It ran kinda rough, but it ran. Does this mean that it is definately the MAF sensor? And can/should the car be driven like that? I swear I could almost smell the gas from it running lean.

teamdaraptor

No, dont run the car without the MAF. They're expensive to replace, ~200 IIRC.