nyysr

Ok here the deal everything seemed ok till it started doing this weird thing.
ill run the car with no problems what so ever then ill run it hard for a few mins 3-10 and when i come off the gas it will stall and run funny.
some times when i pull over it will start up again but wont go past 1600RPM or it will putter and stall.
i was stuck driving the car home this way last night and it will shift into all gears fine as long as i dont go over 1600 rpm, if i do all i have to do is push in the clutch and put it back into gear as long as the rpm are under 1600 its fine....kinda.
other times it wont start for hours after it cuts out.
its done this over the past 4 days now, it will start up and run the way its suposed to after letting it sit for a few hour.
i disconnected the tps and tried starting it but still no good once it cuts out.
im thinking maybe DME relay?
heres a list of motor mods done to my car.

944 turbo, 150,000 miles with Factory LSD

60-1 turbonetics/kkk hybrid turbo with gapless turbine seal ring

Lindsey racing polished intercooler hardpipes.

Lindsey racing MAF conversion with power perfect maf signal tuner

Polished and ported and intake manifold.

Innovate lm-1 wideband o2 with xd16 display

MAXhp/MAXtune dme tuning software

Labonte motorsports digital metanol injection system with interface display in center console ashtray

Tail 38mm wastegate and manual boost control.

55lb injectors

3.0 bar fpr

Bosch 979 260lph fuel pump.

Stage 2 lindsey racing head

3" exhaust with cat delete pipe, resonator installed at cat location

Original LSD trans rebuilt with new bearings on both input and output shafts.

and thats about it, any ideas what it could be?
thanks for any ideas you can offer before goto the local porsche dealer and get reeeeeemed!
thanks again

PorscheDoc

When was the last time you changed your tps?

nyysr

dont know if it ever was but remember i disconnected it and it still wont start.
i tried starting the car before i took it out with the tps disconnected and it started fine so i shut it down reconnected the tps and took it out for a blast.
all was good till about 5 mins into it on heavy boost it cut out and wouldnt start.
i disconnected the tps and still nothing.

minho78

Ok I have one issue like this also, I think it's my reference and speed harness need to be changed. Like PorscheDoc said it looks like you TPS maybe the problem also. If you are around NYC maybe we can meet.

nyysr

yea deff i would love to meet some fellow 951 owners in NYC (we are far and few in between.

as far as the car it will no longer start with o with out the tps connected, any ideas out there?

quinnfiske

My guess would be the speed and reference sensors (gently wiggle connectons) or the DME itself (check for spark when you are in the no start condition).

nyysr

just checked it theirs no spark, what do you think.

quinnfiske

The way the system works is that the speed and reference sensors measure the crankshaft postition and RPMs and send that to the DME. The DME calculates spark advance and timing and fires an impulse to the primary winding to the coil. This creates the spark. If one of the signals is missing or intermittant, the DME will be confused and won't supply the coil impulse.

The impulse is fired by a transistor mounted on a heat sink inside the DME. The leads into the circuit board have been known to develop cracks and make intermittant contact. So no spark. This has happened to me.

Other possibilities include a bad igntion switch or a bad coil (unlikely but possible).

With the ignotion on, there should be 12V between the small coil terminals and ground. The impulse from the DME is to ground.

quinnfiske

I should add that it may also be the DME relay inside the fuse/relay box. This turns the DME on when the ignition is turned on. These have been known to fail, but it has never happened to me. I carry a spare anyway.

nyysr

if this part fails would it also cause the car to have no spark.
i should also note that the DME relay gets warm, not hot but good and warm.
i dont know if this is out of the norm for the DME relay.

Luis de Prat

This sounds like there may be some broken solder joints inside the DME itself. What happens is the car runs normally until the DME heats up and the cracks in the solder joints stop making good contact, hence the erratic behavior.

You should try a test swapping yours with a known good DME for your year and model, and see if the problem persists. Good luck with it.

nyysr

yea im thinking its either that or the DME relay.
ill pick up a relay tomorrow and keep my fingers crossed if not ill try and look for someone who has a 1988 DME for me to try out, thats not going to be so easy here in new york.
thank you all for your help i truly appreciate it, now wish me luck lol
hey can anyone reccomend a good Mec in NYC or the 5 boroughs?

quinnfiske

My DME relay never really gets hot as far as I know. You can make a jumper to bypass it and see if that makes the problem go away.

The 951's all have the same DME. The 951S has different maps.

JohnKoaWood

Functionally the DME programming is the same..

BUT

86 & 87 951 DMEs are 24 pin chips, 88+ are 28 pin chips...

Best bet would be same year... BUT a 24 pin DME SHOULD work with a 88..just not 100% sure, I would have to check the schematics...

There is a recycler in NY.. (can't recal their name right now, and I'm at work so I don't have my bookmarks...) they should have an 88 951 DME... or just ask for someone parting a car... you could also use an S DME, with your chips in it.... just swap the chips and go.. this won't work with a 86 or 87 DME/KLR pair though..

quinnfiske

Thanks for correcting that. I do not want to spread incorrect information.