80, 2.0., 4 cyl., 1994 - Need HELP

[Arje]

Hey guys, I’ve owned a ’94 80 2.0 litre manual, for about 6 months and it’s developed an infuriating fault and I’m needing any help and/or advice I can find. So here goes….

Symptoms:

It starts up fine and runs sweetly for any given amount of time, until engine suddenly dies without warning. I’ve been travelling at speeds between 20-70 kmh when the revs suddenly drop to nothing and the engine stops. Sometimes it restarts right away and may not do the fault for a few minutes, other times it starts but higher revs can only be maintained by constant accelerator pressure, etc. At times you can drive it for a week and its sweet – till it once again dies. A couple of times just as you start the engine the revs drop below normal idle range and revs are ‘roughly’ kicked back up to about 800 rpm - this doesn’t always happen and I’m not sure if there is a connection between this and the fault.

What I know:

1) The ECU reports no error codes.
2) The fuel pump is new and was replaced less than 2000 km ago.
3) Coil pack unit is new - it was installed in the hope that it was a weak spark problem, but the fault occurred within minutes of this.
4) Fuel pressure in the system has been tested and is fine.

We’ve been thinking it has to be an electrical issue, possibly a loose wire or connection. We’re in the process of removing all connections, cleaning and reconnecting all plugs, but still nothing.

Any ideas or has anyone had a similar problem with theirs? Could it be due to a faulty relay in the system? Oxy/lambda sensors? We bought the car from a dealer and I’ve heard that sometimes they have the engine steam-cleaned and this can cause probs- could this be related?

As you can image it is an absolute pain in the a*** and I’m pretty desperate at the moment.

Any advice ideas will be most appreciated. I love this model and it’s a fantastic car to drive – except when it does this sort of thing.

Thanks!

 

[scotty33]

Does it only do this when warmed up? If so it could be damaged/shorted wiring from the lambda probe. The car would also run normally at wide open throttle.

 

[Arje]

Does it only do this when warmed up? If so it could be damaged/shorted wiring from the lambda probe. The car would also run normally at wide open throttle.

It's occurred both shortly after starting (in the morning) and also after the engine has been running for approx. 1/2 hour.

I think it's occurring primarily during low rpm, such as when idling or when coming out of a gear change when clutch is in. I've heard the lambda probe can cause similar probs, but the lack of error codes and the fact that once the engine is running it runs smoothly across the rev range, made me think it could be something else.

Thanks for the tip - at the moment i'm not ruling ANYTHING out, so I'll try to check the wiring around the probe also.

Cheers.

 

[scotty33]

If it does this cold, then I doubt the lambda is the problem. It's signals are not used by the ECU until the engine is warmed up. Sorry I can't think of anything else that fits your symptoms, good luck with it.

 

[Rev-head]

Just an idea.........., problem happens when the car is hot?.......sounds like it might be drawing in air from some were .sound like something is expanding with heat and letting in air then contracting when cold would check all pipes that connect to inlet manifold...manifold gasket........when the car is hot spray WD40 over the pipes ..inlet connection and see if the engine running changes

 

[enda1]

is the car a single point carburettor type fuel injection or multipoint injection. What is the engine code?
Try running the engine at about 3000 rpm in neutral and see if the revs hold steady or if the revs hunt up and down.

 

[Arje]

Just an idea.........., problem happens when the car is hot?.......sounds like it might be drawing in air from some were .sound like something is expanding with heat and letting in air then contracting when cold would check all pipes that connect to inlet manifold...manifold gasket........when the car is hot spray WD40 over the pipes ..inlet connection and see if the engine running changes

Sounds like a good tip. I'd looked at all the pipes for obvious cracks, etc. and having seen none, I assumed they were ok. I'll try the WD40 thing and see.

is the car a single point carburettor type fuel injection or multipoint injection. What is the engine code?
Try running the engine at about 3000 rpm in neutral and see if the revs hold steady or if the revs hunt up and down.

I don't have the engine code with me at work, but i think its a single point style EFI (?). I tried the rpm thing you suggested and revs are holding steady. The times that it's played up the revs dropped rapidly and to avoid stalling the engine you have to maintain high revs and even then the rpm fluctuates.

Thanks guys for taking the time. I'll keep you posted on developments.....hopefully good ones!

 

[audi5e]

I am not sure which fuel system your model is using, however most models use a dedicated idle circuit, if something goes faulty in there then...

Try checking the idle switch, normally somewhere near the throttle body. If your model uses one, then try cleaning out the idle stabiliser.

Also as Rev-head has pointed out, check for vacuum leaks. These are infriatingly common in an older car. In fact it is worthwhile changing all vacuum hoses.

Hope some of this helps.
Gordon

 

[enda1]

I had a problem with my single point injector system where the car wouldn't hold at idle and at higher revs the engine was constantly hunting up and down, and the problem was intermittent. Turned out it was the throttle position sensor on the side of the throttle body. This unit monitors the position of the thottle and controls the idle so this might be your problem. Its a small black plastic unit held in with 2 allen screws and has an electrical connector on it. Once I changed it everything was fine.

Arje. If you can send me an email address by PM then I can send your the fault diagnosis and repair procedures, from elsawin, for this single point injection module

 

[Arje]

Just thought I'd post a quick update on the 80.

After running out of ideas and doing everything we could to it, we finally took it to and Audi enthusiast who had it for nearly 3 weeks. During the first week and a half it did not fail and just as I was about to go and collect it, it failed on him!

He noticed a slight backfire just as it failed and thought it was probably caused by a faulty heat sensor in the air flow/mass meter. He replaced it with a semi-new one and whoalla!, the car has been runny faultlessly for the last month!

I hope that's the last of the dramas for now.

A big thank-you to everyone who posted with suggestions.

Cheers,

Arje