About 9 mths ago, when starting the car, it would burst into life immediately. Within less than a second, it would start, revs would jump to about 1600rpm, then settle to 850rpm approx.

All seemed perfect on starting, but I had the common idle dipping. To try to resolve the idle dipping (I may or may not have a LWF), I have tried:
- new ISV
- Steve Wong chip
- new coils
- new fuel filler neck & cap
- checked for vacuum leaks
- new air filter
- cleaned AFM
- fuel injector cleaner fuel additive
- new oxygen sensor

I still have the idle dipping but fortunately it never stalls.

However in the last month, the car has been slightly harder to start. It doesn't seem to catch & burst into life on the first attempt. It takes an extra second of starting, then maybe 1 or 2 cylinders fire, but it doesn't catch & start. Then on the second attempt, it is a quick start, but when it does start it does not rev to 1600rpm and settle, it just starts up at 850rpm. This only happens when cold and hot starts are normal. But the starts are definitely different to 9 mths ago.

There is also a very slight hesitation when taking off when cold. Just a slight variation in power when holding the throttle in the same position and accelerating from 2,000 to 4,000rpm.

Any ideas guys?

 

Have you checked for DME error codes? Something seems off, maybe the DME can give you a hint of where to look.

 

The last hammer test was about 4 mths ago. The only faults were apparently very common faults in the HVAC system and the mechanic said it was nothing to worry about. At that time, it had the idle dipping but it didn't have the slightly harder starting.

When you start your car, does it shoot-up to 1600rpm approx rpm and settle to idle, or does it just start at 850rpm straight away?

New distributor caps about 2 years ago and 10,000 miles.

Unsure about leads but they look quite new.

I have a new fuel filter but tried to install on the weekend and couldn't crack open the connection due to the difficult position of arms.

 

When my car starts, it doesn't shoot up to 1600. I haven't watched specifically, but I would say that it goes directly to 850 rpm. No high idle.

 

Mine never had a high idle, it just jumped into life at 1600rpm then quickly dropped and settled at idle.

 

My idle raises a bit above 1000rpm at start up; particularly when it's cold out. Not 1600rpm, but, perhaps, 1200, or 1300rpm. I've even seen it remain about 1000rpm for a few seconds when it's really cold.

I'll take closer notice, but it's getting warm around here (70's yesterday, 50's today) so I don't expect to see it.

I've often wondered about similar conditions to yours. I occasionally get difficult cold starts, but generally the car starts quickly.

I've speculated that the temperature sensor is getting flaky; if that's even possible? It will effect cold starts as it has an affect on mixture.

I've tested mine with the Hammer and it seems to work fine; thus my intermittent speculation.

You can test the temperature sensor with a simple electric meter. Might be worth a try?

Here's a link to test values

 

Thanks.

When you say test at terminals 45 & 30, does this mean that I pull off the plug to the DME and then find those terminals in the DME plug? How do you check the temperature? Do you start the car, read oil temp, turn off, pull out dme plug, test readings, put plug back, restart car, keep warming up, turn off, retest etc. Or maybe start full hot, then check as it cools down?

I think I can google & search to find the terminal diagrams.

Do you have any recommended links to using a multimeter. I have one but I have never learnt how to use it!

Looking at old receipts, my temp sensor was replaced about 3 yrs ago, but it could still a problem I guess.

 

DME pintout diagram can be found in this thread; interestingly, that is a cht thread.

As for reading the values, I happen to have a Hammer so I can read the values live. In your case I'd say that heating the car up, then watching the value fall is the easiest way.

Starting at the connector in the engine bay seems appropriate, too. Then move on to the DME connector.

 

Make sure that the idle switch is closed (throttle cable is adjusted to allow for a bit of slack).

 

Some of the symptoms sound very much air flow related to me. Check that the electrical plug to the back of the air flow meter is pushed home properly and that the thin plastic vacuum line is attached to the back of the air box.

 

What are your thoughts on Bill's suggestion below ...

http://forums.pelicanparts.com/porsc...-gremlins.html

Looking at the parts list, it seems the 964 non-turbo does not have a check valve. maybe not then.

 

just to close out this thread .... the idle problem was finally resolved with a bosch hammer adaptation.

 

So that fixed the starting issue too? I'm starting to have similar problems to you when its below 45* or so out. I can keep it from stalling by giving it a little throttle, but that is quite annoying...

 

opps .. sorry .. i didnt close out the thread very well!

so it was a few months ago now, but i think the idle issue was solved first, but then an intermittent start issue developed. so for start-up it just required a second try and it would burst to life. not too serious but not ideal .... the mechanic suggested gummed-up injectors, and he slipped in some fuel injector cleaner and after a tank or so, it gradually resolved itself and was perfect. he may have also changed the fuel filter at the same time.

 

I too have a harder time on cold start, I am going to clean the ISV and replace the fuel filter today to see if it helps. This winter I will send out the injectors and clean all the intake parts.