munro

Hi peeps, hope someone can help I am new to the world of Porsche and have bought a big pig of ebay. I have fixed everything electrical and the head gaskets, but the bloody thing is still not quite right. it will tick over perfect and smooth cold or hot and revs up nice but cuts out after revving when cold so it stalls at every junction for 15 mins until it gets up to temperature has anyone had this before ??

SQLGuy

A bit more detail would help. First of all, what model of '83 (Euro, US, etc)?

Second, does it start and idle OK when cold, or does it need a bit of gas pedal to start or not to stall after starting?

Third, once warmed up, does it idle OK and does it return to idle correctly after revving? Does the A/C work? If so, turn on the A/C once it's warmed up and see whether the idle rises a little bit, stays the same, or drops.

I'm trying to isolate whether the idle stabilizer is OK. My first guess for a vehicle that stalls when cold but idles OK when warm is that it's too rich. Overrich gets better with temperature, so it could be always overrich, or could be too rich when cold due to a bad warm up regulator.

Try starting it cold, let it idle for two minutes or so, and check the plugs. Also check the plugs after warming up and running for a while. Let us know what you find from there.

Cheers,
Paul

Hilton

Welcome Munro, you've come to the right place to get help with your 928

First order of business.. pics of the car!

Also - is it a US-delivered car, or a RoW (Rest of World)? In '83 model year, the RoW cars had different fuel injection to US cars (Bosch K-jet vs. L-jet), which will make a big difference.

munro

Sorry folks it’s a Euro with the bosh mechanical injection a bit like the old ford XR3s. and yes its starts and idols fine when cold, its only when you rev from cold it feels like the revs drop fast and below tick over and cuts out and can take 10 seconds or so to restart. When it is up to working temperature a can hear something catching the revs as they fall and seams to put them down gently on tick over ?

SQLGuy

Sounds like the idle stabilizer is OK. Probably too rich, at least when cold. Do the after-cold, and after-hot plug checks as I described above and let us know the results.

GlenL

This car has CIS fuel injection. There is no "idle stabilizer."

I would first look for a vacuum leak.

docmirror

It does have an idle bypass valve which does the job. Vac leaks are legendary. Then, remove the air bypass valve up near the front of the spider body and clean it. Also, look for broken bits letting air in somewhere.

If that fails, you'll need to take the CIS head off and have it cleaned well. They don't like to sit without driving.

munro

Ok thanks folks I will post some pics tomorrow, and will look for air leaks and check the mixture.
Thanks Munro

SQLGuy

Sorry, my bad. Didn't realize it was still using the older setup. My '86 CIS Golf GTI had an idle stabilizer, but my '78 CIS BMW 320i had an auxillary air valve instead.

blown 87

It is hard to have a engine that runs well hot be to rich when cold.

SQLGuy

Well is a relative term.

In general, effects of overrich mixtures are more obvious on cold engines (stalling when let off of throttle), and effects of overlean mixtures are more obvious on hot engines (hanging high when let off throttle).

And, again, if the base mixture is correct, but the WUR is providing too much fuel during warm-up, it could well be too rich only when cold.

The plugs will tell.