I thought going WOT ignored all inputs but i never saw someone say it so I wasnt sure. I don't really want to repositioning the arms on the AFM and it was a maybe so I probably won't do it. I haven't tested the TPS I need to, I pushed it off a few weeks ago and never did it out of laziness. I'll be sure to check that tomorrow and inform the thread of its performance

It's just weird now that my issue of it breaking up had flipped. Used to break up under anyload when warm except WOT. Now after running the DME temperature sensor outside of the engine to make the car think its cold my issue is flipped. It runs great when warm under any load except WOT, the only time it breaks up now is WOT.

 

Repositioning the AFM pickup arms is a very common practice and has been done by countless 944 owners. This fixed my own AFM issue I was having last summer (with the exact symptoms as the OP described) - so this is why I am recommending this is done. Of course, this may not be the solution, but its highly recommended as something to try.

There are many resources online for clutch replacement if you search youtube or google. Being a DIY mechanic also requires being good at doing your own research and planning before attempting a job you are unfamilar with. You should do more research (ie: google "porsche 944 rubber centered clutch forum") to determine if your issue is similar to what others have experienced when their rubber centered clutch has failed.

Here is an excellent video from Van on a clutch replacement - the thumbnail shows the torn rubber centered clutch.

 

The fact that having your coolant sensor in the block causes it to run incorrectly, indicates that you have a short in the harness. When the coolant sensor is in the block, it probably grounds the sensor wire going to the DME. Easy to test by touching the coolant sensor to the block while running.

Again, don’t bend the arm on the AFM. Why would you? It runs fine as you said. Besides, you will never get the pressure of the arm right and can cause premature wear of the resistance material. There is a much better way if you really have to, but this isn’t your problem.

 

I think the main clue that the AFM is the culprit is the hesitation and stumbling. This is a common symptom of worn AFM pickup points and is documented throughout the forums and Clarks. I experienced this myself first hand and moving the pickups solved my issue.

Ultimately its the OP's choice but again Clarks indicates this very clearly as a possible cause of the symptoms he is experiencing and the suggested fix is to reposition the arms (slightly).

I say do what you want, its your car. Im just trying to help you get it fixed.

 

I don't think you should over-analyze the symptoms. Running with the DME water temp sensor out and sensing a cooler engine might flip it from running lean at WOT to running rich at WOT and it might be hard to tell the difference.
I don't think the WOT maps are totally static, I'd be surprised if the WOT map did not look at some temp inputs, Baro, etc. Some posters say the AFM is in play at WOT also, not sure what is correct.
Does it stay in open-loop in the DME water temp sensor is reading low? I was leaning towards an issue where closed-loop operation was a problem and that was why it ran OK at WOT, thus my suggestion to try stubbing the DME water temp sensor and (in a different test) disconnecting the O2 sensor.

Retracking the AFM and checking the WOT switch operation seem like reasonable next steps, also agree that the temp sensor wiring should be checked back in the loom. I'm still curious if running in open-loop is masking the issue.
It could be as simple as the DME water temp fakeout is just making it run rich now and sidestepping the non-WOT issue, then it's pig rich at WOT and falling flat. Can you see black smoke at WOT?

If non-WOT operation was bad with the DME water temp sensor in play and better with it stubbed out, then either the DME water temp sensor (or related wiring) has an issue at some temps OR stubbing it out is skewing the mixture back into an acceptable range, compensating for another sensor issue. Or something with the fuel pressure.

If it still has a cold start problem with the DME temp sensor hooked up normally that would be a great place to start looking for the actual problem. After the straightforward stuff like the wiring, blown FPR or damper, etc.

 

I quickly reviewed the entire posting. I do not believe there is a discussion on fuel pressure. The symptoms described indicate a rich fuel mixture.

On initial cold engine startup, the fuel/air is 200% richer because there is condensation of the vapor mixture on the internal cylinder and the mixture is poorly atomized. As the engine temperature increases, fuel/air mixture richness is reduced because vapor atomization is better thru higher internal cylinder temperature,. At operating engine temperature, the fuel/air ratio is a small percentage above stochiometric across the entire throttle range.

A rich fuel mixture can occur at operating engine temperature if the the fuel pressure regulator has failed. The FPR fails closed.
I had this situation occur in my race car engine and there was only one sweet spot at high rpm that the engine would run without hesitation. It was less than WOT.

Test fuel pressure per Clark's Garage procedures.

 

Could be. The no-start slow-start is a nice situation from which to get some info. Assuming there isn't fuel on the wrong side of the FPR or damper or other obvious stuff.
Put in nice clean dry plugs
Crank and let it not start or struggle
Cut it off and whip out the plugs, let us know what you see?

I like the idea of testing the fuel pressure but for many this is asking for a fuel spray and possible fire. If you do test fuel pressure use a DME jumper wire and do not crank the car to reduce the chance of a Long Beach BBQ.

 

Wow, this thread blew up yesterday. Only just got an email today about it.

Clear things up: My first issue with the car was a no start condition. It was caused by a bad DME making the car run so rich it would just fowl the plugs and flood the engine. Then I also had a bad coil. I replaced both and the car started. My first cold start was rough and I had to keep it running by giving it gas, first start in roughly a month. The car ran the best it ever had for me, no hesitations, no break ups. Any percentage of throttle at any engine temperature it would go. After that drive it changed, something happened. The only out of place thing that happened on the drive was the coolant temperature got to 200F, I wasn't looking at the temperature gauge the whole drive, but I saw it at 200F. My radiator fans were tied into the A/C switch at some point in the cars life, so they aren't auto, I have to manually turn them on. So I let it take a little cool down time, driving around then took it home.

Still clearing things up but on to the 2nd start: The second time I went to start it after fixing it, it started right up like a brand new car, first second you bump the starter no problem starts right up. Then I took it on a drive and that's when it first started to break up when warm and under load except WOT.

DME Temperature Sensor Situation: I felt my issue was coming from the temperature sensor, its ohm readings were all over the place. So I ordered up a new one, which didn't end up working for the car, wouldn't even idle on it. Then I plugged my old one back in, started no problem. So I had the new one installed into the car unplugged, I then plugged in the old one and let it rest in the engine bay. When I took it for a drive it ran great at all ranges in the pedal except WOT. It would break up at WOT, I think there was some black smoke from the back at WOT, its hard to remember. So the car drove fine as long as you weren't acting a fool.

Yesterday: Yesterday was a interesting experience to say the least. I was driving the car around, put a few miles on it and I stopped in a parking lot to see if I could get going in 2nd gear. I did it once but on the 2nd time I stalled. Then I tried to start it and it wouldn't start, I saw my coolant temp at 200F once again. I turned on the radiator fans and waited for someone to come get me since I was only 7 blocks from home. I went and grabbed some tools- ratchet, extension, socket, magnet on a stick, towels, Brakleen (Non-flammable kind). I pulled all the plugs and cleaned them (Easiest solution at the time) then cranked the car with no plugs, I didn't see anything come out. The plugs looked a little richer than expected but it wasn't horrible, better than the ones that ran on the old DME. I put the plugs back in and after a second of cranking it started. I drove it straight home and parked it, haven't driven it since.

Hope this clears everything up, I tried to read everything y'all said and when I get back home today I will take another look at the thread and try to do everything y'all suggested.

Edit: I reviewed what I read early on the thread and I guess I should note the fuel pressure likes to be a 33 psi. I also have a solid state DME relay from FTech9 with the 3 second fuel pump prime so no need for jumpers .

Another edit: Just went outside to start the car to listen for bad lifters/collapsed lifters. I think I have quite a few bad lifters based off what I heard but I put my stethoscope back in my garage, so I turned off the car so I could unlock my garage then tried to start the car again and it didn't start back up. I plugged the DME connector into the new DME temperature sensor which I previously said it wouldn't idle on, I started it on that sensor and let it idle till it died. The new DME temperature sensor makes it go lean so there was extra fuel for it to run on from the original sensor, then I plugged the original dangly DME temperature sensor back in and it started. Drove it for 4 miles, felt good, drives normal, didn't go WOT. The car was at operating temperature but I turned on the fans and it stayed the same, so I think I have a bubble in the coolant system because of how many times I've removed the DME temperature sensor.

Thanks,
TurrFinn

 

Update: Went to Lindsey Racing and picked up the DME temperature sensor they had in stock, I tried to start it and it ran poorly and would die out. The car only runs on the DME temperature sensor that was originally in it. Its kind of pushing me to the O2 sensor. Makes me think there might be 2 faulty parts working together to make the car work.

Edit: Was just looking at symptoms for other 944 owners bad O2 and I found this quote that is spot on with my issue, whilst the original DME temperature sensor was in the block. I also discovered the O2 sensor is disconnected. PO said he would disconnect it to make the car cold start better.

 

Did you Ohm test the DME temp sensors? You can determine, for sure, which parts are good or bad. Also, test the Old one. What are the Ohm readings for each sensor?

 

I have tested the original sensor in the car and I think based on my temperature, that the ohm was off, especially when hot. I don't recall the ohms, they are somewhere in the forums, I'll try to find them and post them tomorrow considering how late it is. I assumed based off the sensors readings that it would be bad but I tried 4 different sensors and none of them worked. Makes me think that something else is wrong and the 2 wrongs are making a right.

TurrFinn

 

All the weird readings from the DME water temp sensors is unlikely. More likely IMO is that you are not getting a good reading with your multimeter.
Re-tracking the AFM is good advice IMO. I suggest putting the car together with whatever temp sensor you like and clean fresh plugs, try to cold start it and then see if you have a problem cold starting what that problem is.
Focus on the cold start as that is a simple basic situation that is easier to diagnose than driving in or out of closed-loop and WOT and whatnot.
If it fails to cold start, stop right there and check the plugs. If it does start, let it idle for 5 min and then shut it down and check the plugs. We'll go from there.

 

Follow up with my car, issue is solved, I was just a fool lol.

Link:https://rennlist.com/forums/924-931-...-no-start.html