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924S Running issues with video (Read 1012 times)
TheReal244
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924S Running issues with video
Oct 27th, 2016 at 1:06am
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Having trouble with my 87 924S after going through just about everything that I can think of. It is idling very roughly and high. Frequently missing and occasionally backfiring. It will sputter and die if I don't keep my foot on the gas until it warms up. Here is a video:  Sometimes, it will die when trying to idle. Then occasionally, white "mist" (not really smoke as far as I can tell) comes out of the intake very slowly and dissipates very slowly. Looks like coolant to me?

It was running fine in 2013, then one day would not start. I cleaned starter and ground contacts, and found that fuel pump was dead. Replaced it, fuel filter, and the fuel lines with push-lock hoses and AN fittings and then got it to fire up but it immediately ran approximately the way that it does now. Got a fuel pressure gauge and fuel pressure seems to be at spec. Replaced spark plugs, wires, cap and rotor, speed and reference sensors, throttle position switch, adjusted MAF to spec, checked for all vacuum leaks and replaced all hoses. Checked DME Temp Sensor.  Rebuilt injectors from witchhunter - verifed they spray evenly.  Replaced the ECU with a rebuilt one.

Brought the car to a Porsche specialist and they supposedly tested everything but could not figure it out without opening up the engine. To them, it sounded like a broken valve spring. So I began to tear it apart myself. There was no broken valve spring. Had the head professionally rebuilt for good measure. Replaced gaskets, timing belt, balance belt, water pump and all rollers/bearings. Verified timing is correct per marks. (have not checked with a timing light but it should be ok?). Cleaned all grounds under hood and chassis. Tested ignition switch and new fuel pump relay. Compression was consistent (average 185? iirc) within 5 psi of each other on all cylinders. Tried BG-44K fuel additive and 93 octane fuel. I am sure that I have tested other things that I am not thinking of right now.

Here is a video of it running (at first I have my foot on the gas a bit to keep it running):  https://www.youtube.com/watch?feature=player_embedded&v=pnwuHBbJUzI

Any idea what else I should try?
  
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Zündfolge
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Re: 924S Running issues with video
Reply #1 - Nov 16th, 2016 at 7:50pm
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Sorry to hear - idle control valve and throttle position sensor would be candidates. Edit: TPS is new, I see now.
I didn't quite follow whether it improves when the engine is warm?
  

Wheelwell ate my workshop log.
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Conradk
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Re: 924S Running issues with video
Reply #2 - Feb 23rd, 2019 at 2:35pm
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FWIW,

my son and I chased a similar issue and it ended up being the DME/ECU. I bought a supposed rebuilt one and same issue. So I had ruled it out and we and/or several shops had already replaced everything working down the poor running checklist. Hot it would run better than cold it would not run at all.

I usually don’t throw parts but like yours the car had sat for a long period so was good to replace anyways.

Eventually took it to a third specialist further away who ‘walked through the circuit’ and both DMEs had bad solder connections. So we paid for another rebuild.

Also, we still need to replace the intake gaskets. That will make it idle like a dog also.
« Last Edit: Feb 23rd, 2019 at 8:03pm by Conradk »  
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