Gage

Does the car exhibit the same symptoms if you remove the DME relay and connect terminals 87 and 87B with the power terminal 30?
Can you cause the car to stall by wiggling the ignition key in the run position?

Gasngo

Its a shot in the dark for sure but worth a try. I really need to reread the entire post to get a feel for what going on but what you are saying is on start up the motor will fire off but will stumble and not quite catch all cylinders then die. Restarts are all the same. Or does it finally catch and smooth out. You mentioned when you apply throttle is dies and back fires at times?

walfreyydo

Does the car exhibit the same symptoms when the DME relay is jumpered?
Checking the operation of the idle control valve would also be worth a shot. It should click when you run some voltage through it.

papasmurf

It kind of does both. It has not run really at all the last few days I have worked on it aside from the odd start that might last one or two seconds at 1k rpm before dying. Most of the time it was dying just about as fast as you would turn the key but it was firing in that I was not just cranking on it without spark/ignition. Yesterday it started to behave closer to how it was when this thread began a few weeks back where it would stumble/run rough at low rpms several attempts in a row before catching and running somewhat better but there was still hesitation and stumbling when you applied throttle particularly if I revved it to per say 3k, let off the gas, and applied throttle again...it would choke down to near dying and if you were not very gentle with the throttle input, would backfire. When I first started this thread it was having a hard time starting where it would take 4-5 attempts where it would run rough at low rpm but usually after the 5th or so try would suddenly gain it's footing and idle at 1k without issue. I had never had the stumbling and rough running when revving the car before that point either. That seemed to occur after changing the TPS but I have swapped the TPS between the two I have on hand several times but have not found the car to run smooth again regardless. The DME relay I have is the F9 tech relay so it is not a mechanical relay like the original part is. I can make the jumper if you think it is worth a try...I probably still have the older DME relay that I think is working still too.

Gage

Yes, make a nice 3 way jumper, at least 6" long, no 944 owners toolbox (and glovebox) should be without one. Connect to the 30 terminal last when installing the jumper and disconnect from the 30 terminal first when removing.
Also check the ground from firewall to the engine and the fuel injection harness ground on the back of the block.

papasmurf

Been under the weather the past week or so but got to work on the car some more this evening. The car started using my dme relay after 3-4 tries but didn't run great as it would stumble if you let off the throttle after holding it steady at 2k and applied throttle again. Only if you were very gentle with throttle application would keep it from dropping down to 700k rpms and stumbling before idling back to 1k. I pulled the relay and made a jumper and got the same basic results...the car started after a try or two but idled rough/low for the first 10-15 seconds. Fuel pump was running the entire time as expected. I still need to pull the manifold I guess and check/clean the idle valve.

papasmurf

A bit of good new finally...I did a smoke test on the vacuum lines last week and found some leaking hoses under the manifold from the AOS and idle valve. A bit strange that they both decided to start leaking all of the sudden as I did a vacuum test about a year ago when I first got the car back together and had all the leaks sorted out then. I replaced the AOS hose this weekend, cleaned the idle valve again, replaced the hose from the manifold (no way am I paying $130 for that "j" hose) and put it all back together this evening. The car did not start immediately and seemed to just turn over and die like it has before but of course I had the fuel system somewhat apart again to fix all the hoses so it did start on about the third or fourth try and ran mostly decent but not what I would call 100%. Since I have had this car, it seems the idle speed changes just about every time I start it and I have to adjust it on the TB. I am not sure if the idle screw is loose and turning as the engine vibrates (I can't see that really happening every time) but I had to adjust it again this evening. The car was still showing some hesitation when throttle was applied as if you had the throttle pegged at 3k, let off the gas and quickly applied gas again, it might backfire depending on how aggressive you did so...still it was running much better than before with alot less breaking up and stumbling. I think it is still going to need some more fine tuning but assuming nothing changes, it at least runs and is driveable at the moment.

papasmurf

Revisiting this again as the problem is still there for the most part. I purchased the remaining vacuum hoses under the intake manifold to the idle valve, the ($) J shaped hose that mounts under the manifold, and the odd shaped hose in the front under the AFM that t's to the venturi, etc. All of the other hoses have been replaced in the past two years of rebuilding the car. The car usually will idle briefly at very very low (~300) rpm before dying most of the time. Sometimes it will keep running but again at maybe 500 rpm but any attempt to add throttle will kill it. After 4-5 times of trying to crank it like this or letting it idle roughly for a minute it usually will allow you to slowly add throttle and it runs steady as long as you keep your foot on the throttle consistent...any attempt at this point to abruptly add throttle will cause it to stumble and sometimes backfire through the intake. It does this pretty much whether the car is hot or cold as I got it warmed up this evening messing with it and it still didn't like anything other than smooth throttle application. To reiterate the car has a new FPR, F9 DME Relay, DME temp sensor (the one in the head), and in the not too distant past I did almost all the diagnostics on the AFM, TPS, Coils, and checked the injectors for flow, cleaned the idle valve, and checked the fuel pressure at the rail. The car has been driven just 2 or 3 short trips since I was having major issues with it. The gas I just added a week ago so it is fresh. I did notice today after shutting the car down that the FPR is weeping what I am almost certain is oil at its base. I pulled the vacuum lines to the FPR and did not notice any fuel. I also disconnected one of the injector plugs after the 2nd time of trying and failing to keep it running more than a few seconds. It would start and run on 3 about the same as four...maybe slightly better but that could be in my head...at that time it still acted like it would die if you gave it any throttle. I hooked the injector back up and got it to start and idle very low (500rpm) until it seemed to warm up enough to where the idle improved. I did also notice after the car was warmed up that the idle falls to 6-700 rpm when throttle is chopped (typical early 944 issue) but it stays there for about 10 seconds before it will slowly creep back to 900 or so. If you abruptly add throttle before it is back to 900 it almost certainly will stumble and backfire. If you add throttle abruptly once it has idled back to 900 it will rev without backfiring and smoother though it still doesn't like it.

orig944

It would appear that not all cylinders are firing. That is the way my car would react if I let it sit too long and a fuel injector (or two) would get stuck. The fact you can remove an injector plug with no change confirms this. In your case, you have checked that all 4 injectors will spray, so I would look at the ignition side. A car with a weak coil or bad wires or plugs may spark at atmospheric pressure, but not under compression pressure.

Another idea that comes to mind is a plugged exhaust system. It is possible that the catalytic converter overheated due to unburnt fuel reaching it, causing it to melt, and resulting in restricted flow.

orig944

Rereading this thread, your first post exactly describes the symptoms I have had with a stuck injector. After starting, it would run poorly until the injector(s) would free up, typically 15 seconds to a minute or so. You maybe should have another look-see at them.

papasmurf

Got a bit of time to mess with the car this evening and found my spare AFM to swap out and test. I swapped out the AFM before starting the car for the day, and it started immediately the first try and the idle was much better than it had been previously as within a 10-15 seconds of idling I could apply throttle without the car trying to die. The idle is still a bit low at 7-800 rpm but I can live with that for the moment. After the car warmed up a bit I I revved the engine gently and there was just a slight hesitation from time to time but no stumbling or backfiring. I shut the car off and immediately swapped the other AFM into the car and restarted it and the idle performance was about the same as the spare AFM but the car would stumble more when revving and would backfire if pushed too hard like before so I think the AFM is at least partly to blame for my issues. I am going to open it up and see what the sensor tracks look like inside. I did do a smoke test afterwards as well and still have a vacuum leak (has to be a loose clamp as all hoses are new) around the idle valve and it seems the throttle body is leaking slightly where the TPS attaches.

papasmurf

The saga continues...I had a very small vacuum leak at the idle valve as there is a very tiny nut that tightens the "screen/wheel" assembly that is internal to the idle valve that was slightly loose allowing just a tiny bit of air to pass. The AOS o-rings were the ones that were on the car when I first got it and they eventually started to leak there as well when I did a smoke test so I replaced those recently too. The car starts and idles pretty good now and you can rev the engine gently without it stumbling for the most part but it still does not rev smoothly when you give it throttle more aggressively or repeatedly rev/let off/rev in which case it will backfire through the intake if you are too aggressive with throttle input. I am at a loss of what it could be now as I think I have changed out just about everything that could be causing the problem. The DME I don't think would be causing issues as the car starts and idles fine and has run properly on this DME before. I have two DME's and they both seem to operate pretty similar so apart from them both having the same issues it just doesn't seem likely. I retracked the wiper on both my AFM's as you could see a slight groove where it had been before but it did nothing to fix the issue. I have extensively smoke tested the car twice now back to back and it has no leaks. Any ideas what to do next? I feel like I have gone through the clark's troubleshooting manual enough times I have it memorized at this point.

Jfrahm

> I did notice today after shutting the car down that the FPR is weeping what I am almost certain is oil at its base.

Huh? Maybe gas mixed with some of the vacuum line dissolved in gas.

Don't run it if it's super rich, you will wash the oil down (and contaminate the oil in the sump) and scuff the bores.

papasmurf

I put another (good) FPR on it already that was on it previously.

Jfrahm

Good, no new part is ever defective so you are all set there.
But... what about the "oil" dripping from it?