Chunkerz

I'll see if I can scrape together some cash and buy a fuel pressure gauge. The fuel pump worked just fine when I parked the car. Could it fail from just sitting around? I'm assuming it works fine since I can get the car to run if I disconnect the DME coolant temperature sensor and open the throttle. I plan to replace the screen in the tank, but I have a 2/3 full tank of gas and not enough gas cans to store it...
I did some reading and I don't think the turbo DME will work Are there any at home tests I can do to verify my DME is alive, or do I need special equipment?
Not yet.

Van

Easy (and cheap) fuel injector test: pull off the whole fuel rail, injectors included, and leave it hooked up to the supply and return lines. Tilt it up a bit so the injectors are aiming sideways to up. Get in the car and while you're looking under the crack of the hood, briefly turn the key. If the injectors/fuel pressure is good, you'll see each one make a nice little mist of fuel.

F40LM

While here is a good source may I ask if you have any contact with your local PCA chapter? I would bet there are a lot more 944s within a hour of you than the 5 you have seen. And some will be in the PCA and never come here. I bet someone in your PCA could help you locate a spare AFM and DME to try out. Even here in Mississippi we could come up with one for you to try.

All that said, I agree with others it does sound like a vacuum leak. I have never tried it on a 944 but there is the old butane trick to locate one.

Good luck, don't give up on her yet, and keep us posted.

m73m95

A 951 DME will not work.

Find someone to loan you one (I would send you my spare, but I'm not 100% sure it works either lol). There aren't that many possibilities that could cause what you're experiencing.

Someone has to have a spare DME they would be willing to loan out. If you're using the NA tune, then there should be no reason to get an AFM.

Chunkerz

According to my helper all 4 injectors were spraying nice clouds of fuel. While I was in there I went back and verified that I had sparks on all 4 cylinders.
I haven't been in contact with my local PCA yet. Using the butane trick only works if I can keep the car running. Mine dies almost immediately. I'm going to try pressurising my intake tomorrow and see what I find.
I wanted to get an AFM just to verify that it isn't caused by my NA-Tune. I found one for $50, so I'm going to pick it up. If it doesn't fix it, then I can just sell it for $50 again. If going back to an AFM/stock chip doesn't fix it and there are no vacuum leaks then I'll send my DME away to be tested. Was the 1988 DME specific for that year, or could I just buy any late DME (other than one from a 951, S, S2, or 2.7), convert it to 28 pins, insert my chip and be ready to roll?

m73m95

Any late 8v NA DME should work.

16valver

In that case I might put my money on reference sensors. When they start to go they can cause all kinds of weird things to happen to your engine. Pop the manifold off and pull 'em. I bet they don't look to great.

Chunkerz

My tach bounces, so wouldn't that indicate that they are working? I really really really don't want to remove the intake again. I just got it back on yesterday and it was a pain in my *** If I pull them, then I have to gap them again, which I'm not too confident about. Or do I only gap them if I remove the bracket? With my luck I'll probably drop a bolt in the bellhousing...

Nashio

You should pull the intake to see if the intake manifold gaskets are broken. I know when I had a vacuum leak that was the cause and my car would go from 600 rpm to 2000 rpm and then die after a couple seconds and trying to rev it I had misfires.

Chunkerz

The intake manifold gaskets were replaced when I replaced my vacuum lines a few months ago. Should I have changed them again after removing the intake? My surging idle was cured by replacing the larger vacuum lines under the intake, AOS seals, and the ISV. Now it just idles super high until it sputters and dies.

I think I'll test the sensors first and try jiggling the harness before I slice my knuckles open tying to get them out. I did some research and it looks like they're removable without taking off the intake, so I might try it with everything in place before I remove the intake again. I read some horror stories about the sensors breaking off and having to break the bracket in half to get them out. I'll give them a good soak in Koil oil every few hours before I attempt anything...

Thanks a bunch for all of the help so far!

m73m95

Also, with the Rogue Tuning software installed, your car should still run (though not well) with the MAF unplugged. (meaning, I don't think the MAF or AFM is the problem, if you suspect them. There are min/max settings built into the code so the car can "limp" home). The car should idle almost no matter what.

The sensors can indeed give funky signals to the DME if they are covered in metal shavings. It might not be a bad idea to pull them and clean them off. IIRC, if you do happen to break one, the BMW parts are cheaper than the Porsche version.... but are the exact same sensors.

Is the coil good? Any chance coil driver in the DME got burned up?

Chunkerz

I'll try removing the sensors tomorrow and see what I find. I think I might just replace them since they're older than me. The BMW ones are like 35 bucks each, so why not? I get 12 volts at the coil, but my understanding is they don't wear out and get weak. They either work or they don't. Can an ocillescope (no clue how to spell that) be used to test the signal from the sensors? How should the signal look? A nice square wave when the reference sensor senses TDC or something like that? I'm pretty sure I have one somewhere.

16valver

Yeah I think you can get at them without taking it off. Everything is slightly different on my S lol.

Ref sensors should connect down by the bell housing and could very well be covered in anti freeze, metal shavings, oil, dirt or all of the above. Good luck!

16valver

Yep coil's are a solid state unit. Some may be more powerful than others but they either work or they don't.

m73m95

(Someone may correct me on this, as I am getting to the edge of my understand of the DME. However, this is how I understand that it works).

The coil has 2 wires. 12v from the battery, and then the "ground", which is what goes to the DME. The DME uses the ground signal to control things (coil, ICV).

Just because you have 12v to the coil doesn't mean its getting charged. If that circuit in the DME is damaged, then the coil might not be charging enough, or not at all.