AO

I have a problem that's been bugging me for a while. My car is a 82 US spec (non-S).

Here's what's happening. On cold start, the car barely idles (~100 rpms). In fact it will sometimes die. But after about 5 to 10 seconds of this it's like someone flipped a switch and everything runs puurrfect.

Again this is only on cold startups. There are no vacum leaks (that I can find).

Thoughts and ideas?

Randy V

Sounds like either a balky WUR (warm up regulator), a sticking cold start injector, or a failing thermo-time switch.

Or a combination of those.

Sean79 5spd

Mine car is K-jetronic, not sure how startup air & fuel supply are handled on later models but could be a problem with cold control pressure or bypass air valve.

Dennis Wilson

The K jetronic uses an auxillary air regulator to up the idle on cold starts. The extra air mixes with the extra fuel from the cold start valve. The valve is at the right front of the engine. It opens a gate at lower temperatures. Power is supplied from the thermotime switch to close the cold start valve until warmup occurs. Power is supplied to the aux air vave as long as the ignition switch is on. If it is not opening at lower temps the auxillary air valve is probably stuck or broken. You should be able to check it with a light and dental mirror. The amount of opening is dependant upon temperature so in warmer climates you may only be able to see a narrow cresent shaped opening.

Dennis

AO

Where is the thermotime switch? I couldn't find reference to it in the manuals or in PET.

Dennis Wilson

Andrew,

The thermotime switch is located at the front of the engine under the control pressure regulator (WUR). If it was bad the the cold start injector would continue to inject fuel even after warm up. I should have been more explicit in my earlier post. The auxillary air regulator gets continuous power from the ignition and the cold start valve gets power from the thermotime switch.

Dennis

AO

Thanks. Found it. The manual calls it the Temperature Time switch. Sounds like that could be part of my problem. I'll let you know what I find, when I find it.

karl ruiter

I have had loads of experience with EFI problems on 914s. Fortunatly no trouble yet with my '82 (at 150K miles). I have probably chased down more than 100 EFI problems and never once seen a bad injector, although sometimes adding some cleaner to your fuel can make for smoother feel(much more so on 4cyl cars). Most EFI problems are either air leaks or wiring problems. The next biggest thing I have seen are damaged air flow meters or throttle switches. The throttle switches on the early EFI 928 seem much more bullit proof than other porsche models I have worked on. The biggest problems with Air flow meters are wear on the internal electrical contacts and bending of the flapper valve inside. If the car back fires if can bend the flapper valve and then it will stick in some positions at some temperatures. You can find this problem by just moving the valve with your fingers and feeling for any sticking. Regarding the cold start circuit....how cold are you talking about? In southern california you can usually completely disconnect the cold start circuits and not see any effect. If you are living somewhere colder then there might be an issue with your supplimentary air valve. The thing to remember about this valve is that it is be open by default and heat from the motor and an internal electrial heater cause it to close. If there was a wiring problem with it it would simply close more slowly. These are the same technology used on 914s and I have never seen any trouble with the valves themselves, but if it did fail there are two possiblities I can think of here..it could be stuck open or stuck closed. If it was stuck open the idle should be too high once the car warms up, but perhaps the idle speed has been adjusted to compensate for that. If it were stuck closed and it is really cold where you are then perhaps you might see the symptoms you are seeing. They are easy to test. Just blow through the thing with the car cold, the start it and warm it up and blow through it again. Here is one more possiblity...I think I remember noticing on my '79 that if I pulled off the hose on the inlet side of the cold start air valve the engine would die until the cold start valve closed. I'm not really clear on that, but perhaps you have an air leak on the inlet side of your cold start air valve. I don't think the cold start fuel valve has much effect at all except when it is really really cold and you are actually cranking the starter.