951Porschiste

Michelle, I feel for you!

Now that you have tried just about everything, it's time to sit back and maybe retrace your steps from day one. Or if you have the patience do what I do in situations like this and redo the procedure in reverse...IOW disassemble everything step by step and you may stumble unto the problem.

Sorry!

MichelleJD

The next step is to go back to stock injectors or AFM as a baseline. I'm seriously considering stand-alone.

MHT

have you checked the colant temp sensor, if the sensor has failed or if there is a problem with the harness to the sensor the car will run v.v. rich, black smoke rich. With a warm engine the cts should read about 300ohms, if you get something like that check the harness from the sensor to the dme, a broken wire in that harness will be interpreted by the dme as -30 deg. and will result in very rich mixture.

Good luck, Mark T.

MichelleJD

We checked all the wires for continuity and they're good. Where does the DME read temp from?

adrial

What does it do off idle? Will it even rev up at all?

Are you running the stock AFM or MAF?

I hear ya on the standalone. After years of troubleshooting various issues with the nearly 20 year old system... I made the decision a year ago and I am finally 1 step away from turning the key. Don't let that scare you though ... this project wasn't getting much attention and the timeline was stretched even more by the fact that the car has been ~40 mins away from me and that I was replacing the headgasket at the same time.

MichelleJD

Yeah, mine hasn't run for 3 years, so I'm feeling your pain.

I'm running a MAF setup. I have not checked the temp sensor, but I thought the AFM needed the temp sensor to read density and that the MAF reads temp as a constant. Wouldn't I be better off disconnecting the temp sensor?

The car does rev, but the roughness and backfiring increase. I can get the car to move, but it's a real fight.

Spidey944

Normally popping and backfiring is a Timing or Ignition issue. Not to get too basic, but your firing order is all correct and timing marks line up?? Distributer Rotor and screw are all in place and tight??

MM951

Hey Michelle.. very similar issue to the one I'm having. I have not figured mine out yet (very little free time and when there is free time its raining!) but it seems like we both have bigger injectors, maf setup, and a maxtronic in common. I replaced the knock sensor, injector, crank, starter\alternator harness with no improvement.

I recently found that one of the pins in my flywheel ground down even with the fw. I'm sure if its the reference pin or the tdc sensor one. I haven't had a chance to investigate further but I think it might have something to do with it. Have you checked those out?

irrc, the AFM has its own temp sensor (which some people remove and install into their MAF sensor) independant of the dme temp sensor.

hope you find a solution soon...
mike

gregeast

Yep, I was going to guess crossed up plug wires.

MichelleJD

Plug wires are new and I checked the firing order when I installed them. I have not checked the flywheel pin, although I did not remove the flywheel for my clutch job.

gregeast

Just a data point, but when I was chasing a backfire John at Vitesse indicated that a lean condition was actually causing the backfire. Turned out to be vacuum leaks for me...

Arnnworx sells a simple tool that makes it easy to pressurize the intake tract.

I fabbed one out of a piece of PVC and a Schraeder valve but his is so cheap and easy it's probably worth going that route. I pressurized the system and used some soapy water in a spray bottle to spray in the area I heard hissing, made it pretty easy to track down the culprits.

MHT

The DME gets an engine coolant temp. signal from the blue connector at the front of the block under the intake manifold. Coolant temp is one of the main inputs to the ecu as far as mixture determination is concerned. Cold engine-rich mixture and vice-versa. The sensor has a high resistance with the engine cold and the resistance goes down as the engine warms up, so if there is a connection problem at the sensor the computer gets a cold engine signal and richens the mixture. An easy way to see if it is working is to unplug the sensor while the engine is running, it should stall or almost stall.

Good luck, Mark T.

lee101315

But the car was running fine before you did the clutch , and its very easy to damage the pin or sensor if the bellhousing slams on it...

I remember one car that came into my shop last year had the same issue you were speaking of. The car was bounced from shop to shop (even from a porsche dealer) unrepaired. By the time I got the car to work on, everything was new. Injectors, ref sensors, harness, AFM... it even had some spare ecus lying on the carpet. Sure enough, the owner told me it started acting up after the clutch was done. I didnt waste any time, I removed the ref sensors, turned the engine, and of course, the ref sensor pin was damaged.

MM951

=^ really? I need to freakin replace mine. I attempted to remove it without taking anything part but it doesn't seem to be happening. Did you have to remove the flywheel?

mike

MichelleJD

Please tell me you don't have to remove the flywheel!