Please help!!!

[IanEndurer]

Hello all,

I'm hoping you can help me with my 1982 audi coupe 1.9 gt.

When warm/hot the engine idles very low...it does not pick up when I apply the accelerator and stalls...strangely if I turn the headlights on it does allow me to rev the car and it idles ok.

For your info the alternator is fine, coil, dizzy cap, rotor arm, leads and plugs are new.

I believe it to be electrical as when switching the headlights on the rev counter drops to zero and Visa versa. Today the rev counter only worked with lights on. I am surprised this would cause an engine misfire. I have checked grounds on battery and coil and seem good. Any help would be greatly appreciated. When the engine is cold it runs smoothly. Oh and fuse box is new also.

Forgot to mention with multimeter the battery registers at 13.8v and drops to 12.1v when I turn the headlights on.

Many thanks, Ian.

[Steve Q]

Welcome to the forum Ian, you'll find the members on here are a friendly and helpful bunch 🙂 

Is it worth checking the earthing points? 

Or could it be an idle control valve? I know they're prone to failing on the Audi 80 of this era with the 2.0 engine. Also I found this method online: 

"Just pull the fuse(s) for the ECU/ignition timing, wait a few mins then replace them. Next turn the ignition on for 10 seconds, but DO NOT start the engine or move the throttle, then switch off restart the engine (still without moving the throttle). the idle rest to normal and everything was back to normal"

Or my final suggestion is a failing/sticking throttle body. 

Cheers

Steve

[IanEndurer]

Hi Steve,

 

Many thanks for your reply, my car has a carburettor...does this have an idle control valve? I'm a bit miffed why it only does this when hot. The coolant temp sender was corroded so I cleaned that up and cleaned all earthing points. 

Thanks 

Ian.

[Steve Q]

33 minutes ago, IanEndurer said:

Hi Steve,

 

Many thanks for your reply, my car has a carburettor...does this have an idle control valve? I'm a bit miffed why it only does this when hot. The coolant temp sender was corroded so I cleaned that up and cleaned all earthing points. 

Thanks 

Ian.

You're welcome 😊 hmm good question. I'm wondering if it could be the throttle body or carb? 

[IanEndurer]

I've given the carb a good clean out, with it only running with headlights on I think it's an electrical issue. I will keep trying to solve...fast running out of ideas!! Cheers.

[Trevor]

You mention that when you turn the headlights on the voltage drops to 12.1 volts.....is this with the engine running?

 

[IanEndurer]

That's right with the engine running its 12.1v, I'm ordering an alternator for it as the last one I fitted was defective!! Ian.

[IanEndurer]

Do you think the alternator is at fault or the wiring for headlights?? If I put on the rear screen heater the volts do not drop. It only affects the headlights.