924Board.org

[djblackrain]

let me start off by saying i have been through all 41 pages of the forum and I know 2 things for sure.

1. The 1982 931 is a very unique animal
2. Smoothie is everywhere


So the Porsche Mechanic comes in two days, not happy but it is what it is. My problem is, when i drive the car, 1st is really slow, the rest of the gears pull to about 2000rpm, after that the car no longer gains speed and the rpm stil raise, eventually the rpm will lower, without shifting, and the car will accelerate painfully slow. When the car is in nuetral and I step on the gas the rpms raise as normal.

Now...based on what i think Ive learned is it resonable to say that...pressure, somewhere, is NOT being built up enough? As if something is open/vaccum leak. I would assume that I am getting fuel otherwise the car wouldnt go anywhere. Now I would also assume a vaccum leak that would cause so much drama would be major correct? And only AFTER 2000 rpms?

OR could it be my turbo? Like a something stuck open? I dont know much about Porsche turbo set ups, i dont even know if that question makes sense.


I am sorry if i seem dense, this is the oldest car I have ever owned and the first with CIS.
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1982 931

[Maybe924]

head gasket
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1981 931 GT (CGT Intercooled)
1985 911 Targa Carrera (Sold)

[djblackrain]

....really??? and I thought it would something really hard....


what other symptoms could indicate head gasket, I'm not ready to admit to that yet
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1982 931

[ideola]

Have you been here: Sticky: 931 Resuscitation - how to resurrect a long-dead turbo?

Have you pulled the plugs? They should tell at least part of the story, as in running too rich or too lean.

Is the fuel filter new and installed correctly? The proper direction of flow is from the front of the car toward the back of the car. This is counter-intuitive for most folks unfamiliar with these cars, but if you look carefully at where the fuel lines are routed, it's obvious. Trouble is, due to the high pressure produced by the CIS pump, if installed backward, the filter WILL be damaged and MUST be replaced.

Have you performed a CIS system test? If not, invest the $60 for the correct set from JC Whitney, and perform the CIS test. Make sure your WUR is good. Check your frequency valve (disconnect, and test with an ohm meter, should show 3 ohms). Check your cold start valve (CSV) and auxilliary air valve (AAV), as well as the the thermo-time switch (TTS) per instructions in Haynes.

Have you checked the injector flow?

Have you checked the fuel pump capacity? Have you checked for proper voltage at the fuel pump? Insufficient flow can impede the ability of the fuel distributor to function properly, and will obviously affect power.

As for boost / vacuum leaks:
Have you confirmed that the lower charge tube bracket is in place? They often go missing, and when they do, the lower charge tube lifts off under boost, causing massive boost leak, and performance problems.

As for other sources of boost leaks, all of the little black elbows are likely to be shot and leaking. These will not be cheap to replace with OEM parts, but you can get aftermarket silicone elbows that are close enough. All of the normal vacuum lines are also quite likely to be leaking. You can order a variety of lengths of 3.5mm, 14mm, and 19mm ID silicone tubing, and six 19mm elbows to do the whole job (sorry, don't have the total lengths available here at work, they're on an invoice in my file at home). The other big place to check for leaks is the main upper charge tube interface to the throttle body. There are two gaskets there, a black one that you can see from outside, and a red one that is totally enclosed on the inside. Both are likely to be shot if they've not been replaced.

Who is your mechanic? Does he have deep, demonstrable experience with CIS cars? If not, you could end up spending hundreds of dollars and have a car that is more screwed up than when you started. MAKE SURE the Mechanic REALLY knows CIS. Don't care if he's a Porsche mechanic or not. I've seen too many CIS-equipped cars screwed up by supposed german car specialists because they were ill-equipped (knowledge-wise) to work on the CIS system. The DITC ignition only makes it more challenging. But since you have spark, it's doubtful that is the issue.
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erstwhile owner of just about every 924 variant ever made

[Rich H]

[Chrenan]

Couldn't be an auto, didn't think the 931 came with a slush box.

Agree on Dan's point, make sure your guy knows CIS or learn it yourself. Folks familiar with 80's V-dubs usually know CIS inside and out, so that is another option.

Any white smoke out of the exhaust? Sweet smell? Anything that would indicate a head gasket leak? Pull the plugs, are the all the same healthy colour (brownish gray soot covering) or is one really, really clean, as in washed clean by coolant getting into the combustion chamber?
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1987 951 - M193 Version for Japan

[Smoothie]

This is pretty obvious, but read it and its' links if you haven't already. -The "931 Resuscitation - how to resurrect a long-dead turbo" sticky topic at the top of this forum.

Start as always by eliminating all vacuum leaks and being sure the vacuum line routing is complete and correct. Some valve tapping noise is normal with these cars - if there is none, or if it's not noticably louder than most other cars you've heard, then the valves might be adjusted too tight and not closing completely. -Just one of many things that can cause poor performance.
Another thing to check is the distributor "aiming". One oddity of this car is that it has a distributor, and it can be adjusted, but it's stripped down with no innerds - no mech advance, no vac advance, no spark generation, and timing isn't adjustable by turning it. -But it still needs to be aimed correctly within rough limits. Otherwise the spark (with its' timing generated by the crank sensor and DITC (digital ignition timing control) box) can be cut short or even be sent to the wrong cylinder. This could potentially be your problem because timing would be advanced as engine speed increases, and if the distributor aiming is off, the spark may not be able to jump from rotor to cap post due to the mis-alignment.
-But there are other possible causes. Many of them mentioned in the topic I mentioned above and its' link/s.
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"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[djblackrain]

[djblackrain]

[djblackrain]

[Smoothie]

With the engine set at TDC (both cam sprocket and flywheel at TDC), remove the distributor cap and verify that the rotor is aimed directly at the cap post for cylinder #1 (obviously where that post would be if the cap was in place).
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"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[djblackrain]

[ideola]

[ic932]

[924RACR]

Could be all kinds of things; without a complete run through the diagnostics, there's too many possibilities (including quite likely multiple problems).

Good luck with that mechanic; many say they're experienced and competent, only to fail when faced with an S2 Turbo. They're far more complex than your typical 70-80's VW/Audi... sadly.
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype