Audi 100 2.0 AAD tickover VERY high

[tallpaulselfrid]

Hi all,

Have had a few probs with the fueling on my '91 100 (c4) 2.0E. It's an AAD engine.

It was really gutless, so I replaced the distributor and airflow meter.

This cured that problem fine.

Now I have a new problem. When I start the thing, it revs way up the scale on idle. Like 2500 - 3000 rpm! It'll keep this up for about 10 minutes, so it's not the thermo time switch.

I've checked for air leaks, and can't find any obvious ones.

Also when I boot it, there's a couple of seconds of stumble.

I replaced the pump and accumulator about a year back, all be it with second hand items. Could it be these have gone again?

Any ideas would be warmly welcomed! Thanks!

[Crasher]

How did you set the ignition timing? It would be worth getting a fault code read even though the fault code abilities are very limited. I would replace the coolant temperature sensor for the ECU.

[tallpaulselfrid]

Thanks for the reply Crasher!

Set with strobe to marks on timing belt cover.

Was just running that thought through my mind actually. It's always the same, about a dozen different causes running through my head. Like coke build up in the head, air/vacuum leak.

I'll try the temp sensor tomorrow after work, hopefully it'll be that simple.

[Crasher]

It should be set through the bell housing hole on the flywheel and with the ECU in Basic Settings 04, Main Group 000. When you set it on the timing belt cover, did you dial in 6 degrees or set it mark to mark at zero?

Forget coke build up, a vacuum leak is a good possibility. I would personally still start with a fault code read, I hate guessing.

[tallpaulselfrid]

Thanks again for the info. I tried looking for the mark on the bell housing hole. And couldn't find one. Prob my fault, but this car seems to have a few oddities. It may be one of those transition dogs or something. But it's an 8 valve running a 16v ISV, and also has a different water temp/thermo switch to what VAGCAt seems to suggest. Did dial in 6 degrees though, and the car has run fine for a few thousand k before this problem.

There's a guy here that claims to have the diagnostics tools. So i'll take a run up and see what he can do.

Thanks again for all your help, just trying to keep this shed going until I get the A8 in September!

[Crasher]

The ISV should be 034 133 455 B, what number are you using?

[tallpaulselfrid]

Ah well, my theory of the ISV is wrong then, cos that's the one I've got.

I tried different things while the car was revving today. I unplugged the isv and it dropped the revs to normal. However, I reckoned it wasn't the cause but was just doing as it was told. So I unplugged the Thermo time switch. This dropped the revs again. Could this be the problem item.

As you suggested, I will get it on the diagnostics tool. But I also like to try and figure out stuff myself.

[Crasher]

Well you will have two fault codes on there now, for the two items you have disconnected with the ignition on. You will need to do a fault code read, print and clear then run it (say a week) and then read the codes again