944S: challenging DME (?) diagnosis (help?)

gtroth · 05:02 PM

Ok - old problem reared it's ugly head again tonight:

original thread

Summary (if you don't want to follow the link):

Car has cut out when above ~2500rpm when very cold (~6°F). RPM drops to 1000~1200 or so. Otherwise runs like a top (well, the idle has been known to flop when engine is cold - ISV I think - might be relevent).

New:
-cap/rotor/plugs/wires
-FPR
-fuel filter (edit)
-DME Diagnosis and Trouble Shooting procedure from FSM came up with only fuel pressure over spec (hence the new FPR). REF/Speed sensor signal looked right, but amplitude was way over the minimum allowed signal.

New way it failed this time (it has been a while):

Not too cold out tonight (~20°F) and car was real warm after sitting in hours of snow traffic (took 3 hrs to get home, not 30min). I-95 finally cleared and I was moving well when it began cutting out. I was able to mangage it for about 15 miles by shifting back and forth from 3rd to 4th (worked ok since the road was slippery). Eventually parked in the garage and rev'd it up over 5000 a few times while in neutral and it would not cut out (sounded beautiful). So, it needed to be in gear or under load.

I am out of ideas. Anyone?

carsontc · 03-08-2005, 06:37 PM

I had a similar problem that cleared after I cleaned and/or replaced battery cables etc. I think it was mostly the bellhousing/firewall ground strap, but everything looked really bad including starter motor connections. hey...it's had 17 hard winters

DannoXYZ · 03-08-2005, 10:08 PM

I suspect an intake-hose leak somewhere.

Measure the voltage coming out of the AFM and see what it does when the cut-out occurs. THat's pin#7 on the DME, a thin green/red-stripe wire.

gtroth · 03-09-2005, 02:45 PM

Hey, thanks.

I'd love to clean the bell housing ground but I can't see it. Must be harder for the 'S'. Cleaned all others I could find - they din't really look all that bad.

Intake-hose leak - could be (unmetered air, will run lean, lambda rises, DME compensates with more fuel if O2 sensor is working - not sure I understand cutting out...).

AFM voltage - measured this while I moved the flap and it seemed just fine. The problem is rare (happened maybe ~6 times in two years) so catching it for a reading of any kind is going to be tough.

gtroth · 03-09-2005, 06:31 PM

Anyone have experience with the Ignition Control Module (ICM)? My issue seems more like fuel, but one or two guys over on Rennlist have cured similar symtoms by replacing this. I don't usually like to try things without some testing but for ~$50 and considering how intermettent the problem is I might just give it a go.

legion · 03-10-2005, 04:32 AM

I probably have the wrong thing, but when I hear ignition control module, I think of an ignition system with multiple coil packs and computer-controlled ignition. My 944S has a distributor.

gtroth · 03-10-2005, 06:27 PM

I think you also have the ICM, legion. It's mounted to the fender wall behind the driver's head light. p/n 928.602.706.01. Bought one today and try it this weekend. I hate doing things this way.

New today:
Decided to drive it (~18°F) . Began doing it's cut out, so I put the clutch in and rev'd the engine while rolling. Beautiful - no signs of hesitation. Up and down to 5500 rpm no problem. Pulled over and put my spare DME relay in (why not?). Drove it a little and thought I fixed it. Got on the highway and about five minutes later, cut out. Limped home and drove the Integra (I hate that pompous, perfectly reliable car - it mocks me).

If it's warm enough this weekend, I'll measure coil voltage and injector voltages.

gtroth · 03-12-2005, 02:40 PM

Yeah, took her for a spin just to be sure she was misbehaving before taking a crap shoot and swapping the ICM. Of course, she never ran better than she did today - no hesitation, just her usual healthy high reving self. It was alot warmer out (~40°F). I don't know what I'm going to do.