Scirocco Register

Anyone out there know what causes over run?

The cars a '92 GTII with a pierburg carb. Pretty much every time I turn the ignition off, the engine will carry on like putt putt putt putt putt putt putt putt, then rev up on its own and stop.

Afterwards theres a strong smell of oil, which might explain why the air filter was oily last time I changed it. I'm really needing to get this sorted before I put my K&N filter in there.

Help!?

In return, if anyone needs any advice on plumbing/heating? giza shout

Nick.

Hi Nick

Normally with a pierburg carb'd vehicle it's caused by a too high idle speed/choke sticking on.

Other causes include engine overheated / excessive carbon build up in the combustion chamber caused by overheating/mileage/fuel etc

What's your cars tickover speed?

Spot on man.
Nobodys mentioned thoses two things yet.
The engine idles really high, about 2000/1800 rpm.
And... I did kinda overheat it a couple of months ago. If i dont have the heating on full, it overheats in stationary traffic. Dont think the fans coming on.
Think I just need to adjust the idle then? And obviously get the thermostat or something fixed.

Cheers,

Nick.

If there's no coolant in the system, then there's nothing to run against the waxstat to turn the choke off.

I suggest you get the overheating problem looked at first - imperative to protect the engine itself from prolonged damage.

What ever is the cause of the overheating, can I also recommend changing the thermostat anyway. An excessive engine temp can cause the was in the stat to evapourate and then cause the stat to fail closed.

Then I'd look at the carb (if it's still sticking on) although it the coolant has been excessively hot, then the wax in the waxstat could had evapourated away and a new carb waxstat may be needed as well.

It could be a bit of a minefield but I wouldn't suggest driving round in it until it stops overheating.

I Change the wax stat first. Its black and from memory sits just in front of the carb. It has two black hoses coming from it. It solved my run onnnnnnnnnnnnnn. Also, check the distributor is not dirty and warn. Clean the carb by spraying some carb cleaner down it - not too much. Wipe all the rubbish away as well. Have the plugs been changed? I Had the issue of over heating as well and resolved this by changing the waterpump and thermostat and flushing the system - thats if you have not done this. The cars are old and need bits need replacing together rather than piece meal - some may disagree.

Get a garage to check/turn the distributor to see if the timing is ok.

If all fails, do what i did and get weber - far better. Saves loads on fuel. Runs really well too and will save all the agro in finding the problem. let us know how you get on.

good luck

Cheers guys, starting to make sense now.
I'll let you know how I'm getting on with it.
Better advice than my mates. They suggested taking it out and thrashing the life out of it! Reckon I drive too slow.

kagero wrote:They suggested taking it out and thrashing the life out of it! Reckon I drive too slow.

They've possibly hit the nail on the head. You are unlikely to get running on from the idle speed being too high. It's caused by carbon build up in the combustion chamber and the engine running hot. Give it a damn good thrashing, change the plugs and make sure the mixture settings are just right - you'll possibly find it's running a bit lean if it's running hot. This damages your mpg too.

Also, there is a trick you can have a go at with a couple of pints of water. Get the engine warm, remove a small vac hose and stick it in the water. Keep the idle high until all the water's been sucked up. Repeat as much as you feel necessary.

I had the same problem with mine for a few years- tried everything to get it sorted. Eventually I gave in and fitted a Weber carb and now it runs perfectly. I know it's an expensive solution but nothing else worked, and the difference was amazing.

Brunty wrote: Also, there is a trick you can have a go at with a couple of pints of water. Get the engine warm, remove a small vac hose and stick it in the water. Keep the idle high until all the water's been sucked up. Repeat as much as you feel necessary.

Can you explain this brunty? what will it do, why etc?

Thread resurrection!

The water vaporises in the combustion chamber and lifts away carbon deposits. If you've seen the cylinder that has suffered a head gasket failure you'll know that it is much cleaner than the other cylinders, the idea probably came from there. I read about it years ago and tried it out a couple of times.

Also, have a look at the rubber grommet in the inlet manifold. I found on mine that it had degraded so much that it was blocking water from the waxstat. It's only a pound or so from vw but you'll also need to replace the manifold gasket too.

This didn't cure mine however. I did what rosie did and went with the webber. Best £250 quid I ever spent. The pierburg has too many things to go wrong and troubleshoot. Sometimes just cheaper to fit the webber. Relatively easy too.