The_Phantom

I had the same problem. A good european mechanic fixed it when I lived in San Diego. He set the DME to make the fuel mixture richer and it has never happened since no matter what the temperature. When I was reading the 944 FAQs, I came across the instructions for making the adjustment.

http://www.connact.com/~kgross/FAQ/944faq12.html

I love porsche

i have a similar problem with my 924S, in the cold, when i start it, it idles really really rough, and does NOT want to rev at all, after 15 mins its ok, but if i just turn it on and drive, i have a really hard time driving

Porsche-O-Phile

Appreciate all the interest in/contributions to this. I never expected it to be such a common problem! I'm hoping to be able to get my stock chips back in later this week. I'll post results when I do it. I may tinker with the FQS as well - good thought.

my84-944

No kidding, this is a lot more common than I would have thought.
The "when cold" thing does have me a little worried, as mine will do this even when warm. Maybe it is that mine is a little more progressed.
Jeff, I would maybe hold off on the chip swap. I was thinking that this would likely be more vac. or mechanical than a chip issue. You see mine has the stock chip, I think. Hold on I have never looked at it, but I would say it is stock anyway. Remember this all happened a week or so after I replaced the head, due to a t-belt issue. Ran good for a week then just like that, no idle. Something must have let go, cracked or slipped off. I hate electrical, but I think most of the time if it is electrical it will effect several components. I will be looking into this over the weekend or on Monday. I will find this damn thing of go mad trying, and post what if anything I do find on Tuesday.

PeteL

I am going to take a good hard look at the AFM. Seems to me that the car is not getting enough air at cold start, and then once warm it "pops" into a smoother idle. Makes sense to me.

smoemt

Ok this might be really off but its just a thought. When you have colder air, it allows more air to come in (the reason a lot of people want cold air intake). So could this mean we are getting too much air at idle and as we give it throttle we even out the air fuel ratio? meaning we need the air to warm up around the intake to help even out the a/f ratio. Its a long shot but let me know what you guys think.

DLarsen

If you haven't replaced your DME II Sensor (Engine Temp Sensor 944-606-125-00) and the Throttle Valve Switch (944-606-113-01); this may have an affect on cold engine idle performance.
The Engine Temperature Sensor measures engine temperature and converts it into an electrical signal for the control unit. A cold engine signal to the control unit will change the fuel delivery and ignition timing during warm up. I have replaced this sensor 3 times in the 20 yrs I've owned my 944.
If the throttle Valve Switch is not communicating the correct signal to the control unit; the idle speed will be affected. With 15 to 20 years of ago on this switch; deterioration in performance is likely.
The technical instruction by Bosch titled " Combined Ignition and Fuel-Injection System -- Motronic" is a very information reading on the various DME components and operation.

roadrunner

I know this doesn't sound right on my but on my 89 951, I once had a problem where the engine would not idle when cold, and I would have to open the throttle a bit to maintain rpm or the engine would stall. It continue to run very roughly until the coolant temp guage hit the upper end of the white field, then suddenly would surge and smooth out. This was consistent despite the outside temperature.

I was advised by a reputable shop in Anaheim, CA to replace the oxygen sensor, and after I did that, it ran fine. I always thought that warm-up in open loop ignored the sensor...

Porsche-O-Phile

I just tested several types of chips with no change in the symptoms. I'd been running the Weltmeisters and given that I noted no change with any of the following, I'll be going back to them. I tried:

1. Stock chips
2. Weltmeister chips
3. Autothority Stage II chips
4. Guru chips

Symptoms at idle were exactly the same.

I also checked the contacts at the AFM harness, which look fine. I'll next put the Welt. chips back in and take some voltage readings at the AFM with a multimeter. Failing that, I'll mess with the FQS on the DME and report back whether it does anything or not. Failing THAT, I'll try disconnecting the O2 sensor and see if I get any performance variation.

This is an interesting problem to say the least. . .

35thSLP

I am running stock chips, I will be replacing the TVS and looking at the AFM harness as well. I'll try disconnecting the O2 sensor as well and see what happens.

my84-944

Problem SOLVED!!!!!!
Went over to Tom's (StickShift) on Monday and started looking at all of the connections, vac. lines etc...
Tom found that there was a bad connection due to some broken plastic on the connector that holds the clip ring. Big Thanks to Tom for this as I doubt I would have ever found this alone..
Here is a pic of the sensor and its location. I do not know if this will help, but I think it should make a great place to start. I am just glad it was not the AAV.
[IMG]BADCONN[/IMG]
Hope this helps, and sorry for the pic being kind of bad, but this did work for me.

Porsche-O-Phile

So one thing extra to check. Got a better pic showing the exact problem?

BTW I tried every FQS setting - no change in idle performance, so that's out.

Andial951

my-84,

Do you need to take off the intake to access that connection?

Andial951

One more thing to add to this thread.....

I just happened to pick up a copy of "911 & Porsche World" this week and in the back there is a section where you can write in and ask tech questions to the publisher. It was interesting to see a man by the name of Artho van der Westhuizen from South Africa wrote the following about his 944 Turbo...

"I own a 1986 944 Turbo. It's an American-market model that has 135,000 miles on the clock. When the engine is cold it suffers a compete loss of power in the 2000 - 3000 rpm range at part-throttle. But when I apply full throttle it hesitates for a second, and then accelerates. The problem dissapears completely when full running temperature is reached. The car was serviced recently, and I had the fuel/air mixture adjusted, and tried some injector cleaner, but it hasn't improved. The problem really is a nuisance, since I don't want to use exccesive throttle when the engine is cold."

The response from the magazine written by Mr. Peter Tognola was this:

"The car ideally needs to be checked by a good Porsche technician who will take it through a series of tests to identify the problem - although there are some basic checks that you could make yourself before handing the car over. These include the condition of the high-tension ignition components including the spark plugs, plug leads, the distributor cap, the rotar arm, and not least the ignition coil. You may well discover a fault and be able to replace the defective part, otherwise your garage will want first to check the ignition for itself in more detail. Ask you garage to then carry out a cylinder leak-down test to check the mechanical condition of the engine. After confirming that components are serviceable, or renewing any defective parts, a fuel pressure test and injector test should be carried out using the appropriate specialist equipment. A final check should be made on the condition and operation of the turbocharger boost-control system, Check all intake pipes, hoses and intake seals. At this mileage, wear in the turbo's wastegate valve causes poor sealing of the valve, often resulting in a low boost pressure. The boost pressure needs to be tested under load with a pressure gauge attached accurately to show the pressure changes. Assuming that both the intake and the boost system are in good order, a check will then need to be made on the DME system and possibly the boost-control electronics."

To me it seems like the guy isnt sure what the problem is and basically tells the guy to check everything......I mean is it really necessary to check the turbo boost control system? Anyway just sharing what I found but it seems like My-84-944 may have discovered the problem. Has anyone else checked to see if they found a bad connection in the same place?

my84-944

Not at all, but you will need to move the J-boot to get a good look at it. The pic was during my head replacement drama. If you pull it off, the j-boot, and look at the connection you will see how the wire ( C-clamp?) holds the connection tight. If it is cracked or broken like mine it could be the culprit. We used some Dielectric grease (SP ?) and a zip tie to secure it and it seems to be working great. Keep in mind that you will likely HAVE to remove the J boot to get to it openly, and then replace it to test your work, but this is still a quick one compared to the AAV which you would almost need to remove the intake to get to.
I hope this helps, let me know if this works for you.
If so (with all of the posts with like problems) we may be on to something here.
Chris
PS It would also stand to reason that if this sensor was out, it could cause the same issue, so if your connection is good, maybe test the sensor just to be sure.