Engine stalls immediately after starting

[Telster]

I've recently developed a similar problem and it's happening increasingly frequently, although mostly when cold. Perseverance usually gets her started, but it's annoying! In my case I suspect the (after market) immobiliser.

 

[Jonny944CS]

Hello all,
Nothing major, but here's an issue I've had since building the car last year and I'm beginning to run out of things to try....

Model:
1984 944 2.5 8v

Issue:
The starter motor turns over and the engine fires as normal for a second or two, then dies. The only way to prevent this happening is to blip the throttle at just the right moment. The car will then run a little lumpy, then clear.
I'd say it is evident ~95% of the time (hot or cold). Once up and running the car performs and idles fine with no obvious issues.

Things I have tried to test:
- DME and relay
- Fresh battery
- Fuel Pressure Regulator and leak-down test (hot and cold)
- Flywheel reference sensors
- Vacuum Leaks
- Auxiliary Air Valve (appears to move with 12v)
- Coolant temp sensor

Any similar experiences and/or suggestions greatly received.

 

[bmnelsc]

You don't say anything about your air flow meter - possibly worn, corroded or just gummed up contact in AFM at the idle position? So possibly weak signal at start but when you blip the engine the flap moves up to a better contact and things then proceed as normal from there (low idle/start position voltage no longer considered by dme?)

 

[Jonny944CS]

Yes, good point Bruce. Maybe the DME has a start-up map separate from the AFM? I'll have a look inside the unit to see if the tracks look worn or corroded. Thanks.

 

[Mike_Pollock]

If the tracks are worn etc its quite easy to get the contacts to run on a fresh piece of track, just by moving the bracket up or down the spindle.

 

[Jonny944CS]

ORIGINAL: A9XXC If the tracks are worn etc its quite easy to get the contacts to run on a fresh piece of track, just by moving the bracket up or down the spindle.

Like [link=http://www.youtube.com/watch?v=-11J8XawQtc]this.[/link] I guess care needs to be taken so as not to put too much, or too little pressure on the track.

 

[peugeot]

Works a charm jonny done that a while back , cured the bucking bronco affect when drving from cold . Not difficult to do,once you dont dive in ape style.[]

 

[Mike_Pollock]

Yes - just like that!

 

[Outrun944]

I have the exact same problem - general consensus on other topics is the air flow meter... although I'm really scared of taking it out and botching the job! Replacements seem to be around the £350-400 mark cripes! (My startup process is turn the key and hold it for about 3 seconds whilst dipping the accelerator)

 

[Jonny944CS]

SUCCESS! [] - The first thing I tried was to unplug the connector on the Air Flow Meter. The engine duely started up as normal, then died quickly in a slightly different fashion to before. => This suggested to me that the DME was indeed running a 'start-up map' for initial firing of the engine, then switching to Air/Fuel ratio control using information from the AFM. - So, feeling confident that I was on to something, I removed the AFM and airbox (10min job - I chose not to separate them as access to the four M6 fixings can be a little fiddly). - I then carefully cut away the silicon sealant (applied by BOSCH to retain the black plastic cover and prevent moisture ingress) and removed the cover. Encouraginigly everything looked fresh and dry, so i dug out my magnifying glass to inspect the conductive wiper arm track in more detail. - I tried to take a photo of what I could see, but my photography skills were sadly lacking. Basically the clear groove tracks were evident in the conductor surface, and as you would expect, they appeared deeper in the idle to ~2000rpm range. But the conductor material still looked good, even in the deeper groove sections.

Edited image from FR WILK - showing specs of wiper track material The other thing I noticed was a significant amount of conductor material on and around the region of the wiper track (as I have tried to show in this edited image from FR WILK's site). So using a cloth and some panel wipe, I carefully removed all the specs of conductor material.

Wiper material removed I then reassembled the AFM to the car and turned the key => It fired up first time and subjectively drove with improved throttle response between idle and 2000rpm. Since cleaning it yesterday lunchtime, I have probably started the car 6 or 7 times (hot and cold) and each time it has fired up without requiring any throttle inputs [8D]. There is still a slight drop in revs during the transition from start-up map to idle running, but it is a huge improvement on before. I'll give it a few weeks running and see if it continues to perform well. I'm reluctant to mess around with the wiper track position unless I really have to. Thanks for the help and suggestions.