Ignition/Rev Loss Problem

Greetings to all readers,

My next door neighbour has asked me to pass on a question, in the hope of a solution to an issue, which has been haunting her for a good while now.

She has a VW Corrado 2.0 16 valve
United Kingdom N reg, 1995.

She bought it second hand, whose previous owner was a member of a VW Corrado owners club.

It was working fine when she bought it, the problem has arose since.

Basically she says, when she fires the ignition, the revs jump as per usual, then quickly drop to nothing.

If she retries the ignition, nothing happens at all.

She can retry after a good while and it will restart with the initial rev jump.

If she tries the ignition with her foot on the accelerator, it seems to be all good, but once she released the accelerator, the revs drop and it dies again.

I'm quite certain she also stated that some days it is totally fine!

The biggest mystery is, that she's had it in for inspection into our local VW garage, who have run through all their computer tests etc, but all the mechanics are stumped as to where the problem lies - so obvious causes must have been investigated.

Does this ring a bell with anybody? Has anyone had experience with this, or could offer some ideas?

Thank you very much for taking the time to read my post :D

IDLE OR BUCKING PROBLEMS ON 16V CARS:
If your motronic 2.0 16V car starts to idle funny, first thing you should do is go to the dealership, and make sure all the recalls have been fixed. Some cars did have recalls on computer wiring harnesses. Next, It seems that corrosion at the electrical connectors around the engine are to blame for the majority of these idling problems. Go to a good electronics store/warehouse, and get a can of Deoxit contact enhancer spray. It's about $14. Spray the inside of every electrical connector under the hood. The most important ones are the ones around the fuel distributor, one next to the firewall (potentiometer), one on the engine side (differential pressure regulator), and two under the intake boot (emmissions related).

Things that cause erratic idling on all CIS-E or Motronic 16Vs are:

1. the A/C hoses that run along the passenger side fender, next to the fuel distributor. There is an electrical connector on the side of the fuel distributor and the A/C hoses usually end up resting on it. This is not good. Get zip ties and zip tie the hoses so they do not rest on this connector.
2. Check for a small tear underneath the intake boot. Remove it completely to inspect it. This is a very common occurence. Any sort of vacuum leak can cause idling problems.
3. A failing fuel pre-pump. They're $60 bucks and take 20 minutes to replace.
4. A bad idle switch. The idle switch is located on the throttle body, and will cause idling problems if it doesn't engage and/or if it fails.
5. A bad oxygen sensor.

IDLE OR BUCKING PROBLEMS ON 16V CARS:
If your motronic 2.0 16V car starts to idle funny, first thing you should do is go to the dealership, and make sure all the recalls have been fixed. Some cars did have recalls on computer wiring harnesses. Next, It seems that corrosion at the electrical connectors around the engine are to blame for the majority of these idling problems. Go to a good electronics store/warehouse, and get a can of Deoxit contact enhancer spray. It's about $14. Spray the inside of every electrical connector under the hood. The most important ones are the ones around the fuel distributor, one next to the firewall (potentiometer), one on the engine side (differential pressure regulator), and two under the intake boot (emmissions related).

Things that cause erratic idling on all CIS-E or Motronic 16Vs are:

1. the A/C hoses that run along the passenger side fender, next to the fuel distributor. There is an electrical connector on the side of the fuel distributor and the A/C hoses usually end up resting on it. This is not good. Get zip ties and zip tie the hoses so they do not rest on this connector.
2. Check for a small tear underneath the intake boot. Remove it completely to inspect it. This is a very common occurence. Any sort of vacuum leak can cause idling problems.
3. A failing fuel pre-pump. They're $60 bucks and take 20 minutes to replace.
4. A bad idle switch. The idle switch is located on the throttle body, and will cause idling problems if it doesn't engage and/or if it fails.
5. A bad oxygen sensor.

Thank you for this information, you are a wonderful person!

I will pass this onto my friend and see how she gets on.

Kindest regards.