zogster

Thanks! I was on the verge of actually paying an auto electrician or mechanic to come and help me out, but maybe the gods of tyro car maintenance are finally smiling on me. Must be all those tears of bitter frustration I've wept into the engine bay…

gruhsy

Since this is local to you have you considered this? If your DME is acting up.

http://www.augmentautomotive.co.uk/a...rsche-944-ecu/

zogster

Looks good, but an expensive way to go. I really want to get rolling again without spending too much!

zogster

Captain's Log, Stardate 201504.31

I'm not quite out of the woods, but fiddling with the DME seems to have almost resolved things. I suspect that as well as whatever was going on there, there were/are other minor problems that might have contributed to all this hassle. I've taken a few test drives and the results were:

• The car has started *almost* every time, on 20-30 attempts. There was one incident where the engine lost power and died. When I tried restarting, it first started (no hesitation), but then died immediately. Next attempt: started and ran OK. On another occasion I pulled into a garage and turned the engine off. It did not re-start on first attempt, but after I gave everything a long, hard stare, and fiddled with a few connectors, it started again.

• It's mostly running well, but while it seems completely healthy with the loud pedal pressed down, under lighter throttle it sometimes seems less happy. Occasionally it seems to suffer a slight loss of power, a sudden drop of a few hundred revs, at about 2,000rpm. Seems slightly more likely to do it under a trailing throttle, though that might be down to my sample size. On a couple of occasions I experienced a bit of kangaroo-ing (?), that is sudden but slight drop in power followed by restoration, repeated over and over for a few seconds.

• With the engine warm, on startup it idles at about 1,400rpm, but immediately starts speeding up to about 2,200rpm. This takes about 10 seconds, video here: http://dl.dropboxusercontent.com/u/4...4/IMG_2927.MOV

So I think I'll put the undertrays back on, use the car for a few days and see how it goes, then do some more investigating.

zogster

and after another few short trips...

I still have a problem with the engine dying, which it has done about once per trip so far. It seems to mostly happen at about 2,000 rpm, and mostly under a trailing or light throttle. The engine idle sometimes climbs to about 2,700 rpm, and a couple of times I've seen a hiccup in engine revs while idling - a sudden drop of a couple of hundred revs that is immediately restored.

Very aggravating...

Because the problem seems related to engine revs, I'm leaning towards an TPS or AFM issue as the explanation. I had previously checked both and they seemed OK... but the problem is intermittent, so maybe I got lucky/unlucky on the tests.

Will gather more data, tinker a bit more, and start a new thread if trouble continues.

divil

Glad to hear you made some progress! If you're comfortable with a soldering iron you could always try re-flowing the solder joints on the DME. It does sound like that is the issue. I am not sure what the story is with the whole spark thing...i.e why you could only get a spark after narrowing the gap. Were they gapped correctly to begin with (0.7 to 0.8mm)? And did you reduce all of them or just 1 you tested with?

I think the hiccup you're experiencing is probably the same issue, i.e. the DME. If it still happens with the TPS unplugged, you can eliminate the TPS.

zogster

I'm pretty comfortable with a soldering iron, though I'd want to be absolutely sure that it was the DME itself that was the problem before I re-soldered a lot of joints that were probably OK.

Will the car run OK and be drivable without the TPS connected? I started it before with the connector unhooked, but only let it idle.

My feeling is that because the problem happens in a certain rev range that it's more likely to be a sensor/signal problem than the DME, but on the other hand it was fiddling with the DME that seemed to help.

The frustrating thing here is that while I have made progress, I haven't replaced or fixed any clearly malfunctioning thing. Cleaning the DME multiway connector and contacts, and opening up the DME for a clean, seem to have made a big difference, but I didn't find anything clearly broken, and also those steps haven't 100% resolved things.

divil

Assuming it's stock, the car will drive with the TPS disconnected, but you'll have high idle, virtually no boost (maybe 1 or 2 psi) and less timing advance than normal (the DME will go into wide open throttle mode). Still, it should be smooth with no hiccuping or flat spots.

The fact that disturbing the DME connector has improved things is what makes me think of the solder joints, especially the pins for the main harness connector.

zogster

Thanks, I'll try driving without the TPS and see what that feels like.

Driving this evening I experienced another loss of power incident, this time with a backfire just as the car slowed to a stop.

zogster

After a few short trips with TPS disconnected... i think it has to be the cause of the problem. Or at least the most significant remaining factor in my engine trouble.

Running without the TPS it has started every time, never cut out, and never stumbled. Idle is too high.

I've already tried installing another TPS - but it was used and turned out to also not work. So I gritted my teeth and ordered a new wildly overpriced potentiometer.

ehall

SO, I think I read it all. I didn't see where you had tested the actual battery voltage. Have you checked the battery?

jeffro951

Did you ever get a noid light to test power to the injectors? I had bad injector connectors on one of my cars that gave me the exact symptoms you are having, I believe the injectors share the same ground used by the DME to create spark. I have 2 turbos and both of them when peeling back the boots on the injectors revealed blueish corrosion and one was completely shorted. The connector ends are cheap on ebay and can be installed with but connectors if you cant solder but soldering is preferred. I say worth doing anyway as they will fail at some point if they are original. I ran one of my NA cars without the TPS with no issues.

jeffro951

Oops I spoke before watching your video, what I saw on the video makes me think idle stabilizer, try the idle reset procedure found on clarksgarage.

zogster

Thanks for the suggestions chaps.

Battery voltage: yes, checked that, and there's no problem there.

Idle stabilizer is an interesting idea - I'll check that out. (And no, I didn't get Noid lights and do that test because I'm sure it's a spark problem - though for the sake of completeness I should do it.)

Also, I did have one incident the other day of the engine dying again while driving with TPS disconnected, so perhaps the TPS isn't the only thing still at fault...

I still haven't installed a new TPS, and therefore seen how it runs with a definitely-OK unit, as these things seem rather hard to get hold of - albeit I haven't taken the simple but expensive route of getting it from a Porsche dealer. The used one I bought on ebay didn't work, so I ordered a brand new one from an online parts supplier. A few days later they said they couldn't get hold of it, and refunded my money. I've been ringing round and keep being told that it's not in stock, and that the dealer can't get hold of it from Bosch UK or Bosch Germany. So I've just bought another used one from ebay...

(For anyone who might find this useful, the Porsche part number is 951.606.113.00, Bosch part number is 0280120400, Volvo part number is 3517772.)

E-man930

Carefully peel the rubber boot back on each of the four injector connectors and then report your findings.