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1989 944 2.7 winter issues

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gavinbray

New member
Hello,my name is Gavin and i am a new member on here.A couple of months ago i purchased a nice 944 2.7 as a dry weather toy(have always wanted 1) The tax ran out last month so it was time for her to go in the garage for winter time fixes. The first problem i want to address is coldstarting.If the car hasn't been used for a while(overnight) when i start her she won't idle under her own steam,i have to apply revs for a few minutes before she can run on her own and even then its touch and go,once up and running there are no problems.I'm guessing some sort of auto choke to be the problem however just looking at the obvious.Has anyone got any ideas or had the same problem?
Thank you Gavin.
 
There is no autochoke on a fuel injected engine. The mixture is controlled by the DME (ECU) for cold starting and basicly richens up the mix. As for idling the sped is controlled by the DME and the idle stabilisation valve (ISV). This basicly meters air into the intake depending on engine load i.e. charging, AC etc. First thing I would check would be all the ignition parts coil, dizzy, plugs and leads etc. Then look at the Throttle Position Switch and it's operation. It lets the DME know when the car is in idle and brings it off map and hands over to the ISV. Lastly because of it's awkward location I would look at the ISV. People have had good results by having them ultrasonicly cleaned. Also remember many cars are a little lumpy when starting in cold weather, especially a 20 year old large engined one.
 
Sometimes this can be due to a sticky ISV. You can clean the ISV by un-attatching one of the hoses that go into it. It is located under the inlet manifold, but you can remove a hose from the front and squirt some carb cleaner into the ISV and in most cases, if it is a sticky ISV, this solves the problem. But I'd first of all check the Throttle Position Switch - these things don't last forever and the chances are it is the original fittment.
 
LOL i have had many over 20 year old cars with big engines!! Problem is the classics i have had before are old British motors and i didn't really worry about stuff like this as long as it didn't break down on me half way through a journey,for some reason,with a Porsche,i just want it all to work right.Thank you for the answers,what am i looking for with the TPS,just broken bits or are there tests i can carry out?

Thanks Gav
 
Yes there are tests mate. There is a comprehensive guide on Clarke's website. A simple glance at the circuit diagram will tell you exactly what you should expect from the switch. I recently diagnosed my own with a simple jumper wire. The N/A switch is slightly different to the turbo but on the turbo the switch is fed with 5V regulated from the DME and the microswitch closes and feeds the 5V back to the DME. Also check the alignment. It should basicly close with a click when the throttle is shut and open again within 1 dgree of the throttle opening.
 
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