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starts and instantly dies problem UPDATE

eddieedmo

eddieedmo

New member
Today I have driven about locally on a few small trips and all ok , the car has been running fine since last very irregular ( 4 times over 2 yrs ) occurence of overfuelling,erratic idle and misfire when starting from hot.I have not done anything to remedey except clean all connections to ICV , AFM ETC.
Went to local motor factors to get oil for my ladies car service and jumped in and started fine after normal 3 cranks and died instantly ,did this twice and on third attempt started fine and ran ok.
The tacho bounced as usual and fired but died as if plug had been pulled !
I think I have read this could be FPR causing very high fuel pressure and injectors been cut by ECU -is this a good start point to investigate.

Thanks

Nick [:D]
 
FPR is the new DME Nick. Not cheap for your car, but considering how many fail now I wouldnt consider it to have been money wasted even if it doesnt cure your problem. More of a future problem averted...
 
I have had occasional problems with rough running on hot start (solution was to shut off and restart) but I found the problem was due to releasing the ignition key a fraction of a second too soon on startup (e.g. release just as the engine was catching). If I held the key a fraction of a second longer - it would behave normally. Don't really know why other than speculation that a relay wasn't fully energized when I released the key. IMHO its worth checking/lubricating the key cylinder and see what happens. If nothing else - its a cheap and easy job that probably needs doing anyway ...
 
Nick, sorry to hear that. I would be 70% certain your problem is AFM. Its starting with the flap virtually shut, but when it fires the engine moves the flap due to the incoming air flow. It moves it to the most worn area of the unit, and the 0-5v signal goes out of range, due to corrosion, due to lack of use. I would pull the DME relay, (no spark or fuel) and open the throttle (to allow max air flow and movement of AFM wiper) and repeat a few times to try and clean up the AFM wiper. It may work, but the better way is to replace the AFM. It is also possible to move the wiper to a new path, but its delicate and could leave you stranded. good luck George 944t
 
I believe that the AFM signal is not used until the engine actually fires too, with the DME using a fixed set of parameters whilst you are cranking, so this could fit your symptoms. Im not sure how to check without swapping for a known good replacement, though. Usually AFMs can be refurbished effectively and theres a useful video somewhere. Simon
 
Im with George and Simon, but would add that as the AFMs are expensive I would clean and reposition the wiper on the track. It isnt too difficult and that video is good, i found taking the cover off without damaging it was the hardest bit.
 
took AFM off today and checked and all ok steady voltage increase as barn door opened , temp sensor resistance within spec.couldn't reposition wiper arm as the AFM has a 3 contact wiper arm and not enough room to reposition.cleaned swept area with alcohol and got a bit of muck off. So don't think it is the AFM. Will check the FPR next. Running fine at the moment. Heading for the lakes next week so fingers crossed will be ok. Thanks for all the feedback/help Nick [:D]
 
Nick, I'm pleased for you.....and sorry because the fault remains a mystery. Is the connector to the AFM "good", the symptoms are the same as I had for a worn AFM. Maybe the connector was hi resistance due to slight corrosion on one pin which removal / replacement has cleared. Good luck next week George 944t
 
thanks George . nos 3 connector ( input from DME ) was a little discoloured compared to the others before I gave them a clean.Maybe that will be it. Nick [:D]
 
"Totty" is having the same problem with his turbo at the moment. He has a Scivision MAF fitted so no AFM to deal with. Did you get this resolved?
 
Im going to guess that you have a new 3BAR fuel pressure regualtor? FPR is my new go-to diagnosis, but its unlikely if the part is reasonably new. In the same way that the money spent on a new FPR is seldom wasted, Id say the same for the fuel pump on a 944 Turbo. Even if it wasnt the cause then its a likely future failure averted and a useful insurance policy too, when running more boost and using more fuel. I presume that you have replaced the DMW relay? This is actually two separate relays in one case and either can fail or become unrelaible.
 
just seen the post been away for a few days in the lakes. I haven't had the big issue of very rich running or just cutting out immediately after start up since I cleaned the AFM but I think the wear at the low rev end of the swept area could be causing a problem with slightly uneven running at revs below 2000 rpm. Car ran well when away but did emphasise the need to change the g/box mount - rear end shake and banging when giving it full bore up hills ! Nick
 
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