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elitejaso · Joined: 24 Jul 2007 Posts: 143 Location: Melbourne

Hey guys been away for quite a while but have gotten stuck back into the 24.

After replacing the alternator, fuel pump, spark plugs and leads I still have this same problem.
Runs really nice until the engine begins to warm up gets to just below half on the temp gauge, starts to backfire and eventually dies.
In winter i was able to drive this car on short trips but now here in summer starts dieing alot quicker.

Any ideas guys im really stuck?

Just reading the manual and it says something about if the temp sender gets above 50 it retards the fuel, could my temp sender be stuffed?

Gotta love all this old computer stuff

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1981 924 turbo (daily driver)

Khal · Posted: Sat Nov 28, 2009 2:37 pm Post subject:

Do you have the tach. flops? Just drops to zero instantaneously? I like Smoothie's original advice, check the connection on the DITC. Just unplug it and re-seat it. Worked like a champion on mine.

I had a blown headgasket, too. It caused some weird running conditions. Eventually, car wouldn't run right cold, but would run like a champ warm. Didn't seem to lose any power (from the bum-in-seat dyno) but would occassionally hiccup and would blow white intermittently. Very strange. Can't stress enough, with a blown headgasket, it seemed just fine apart from these weird intermittent problems...
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'80 924 Turbo

elitejaso · Joined: 24 Jul 2007 Posts: 143 Location: Melbourne

Yup same thing, backfires for a bit and then all of a sudden u rev it and the tach flops to zero and cuts out.
Unfortunately i couldnt unplug it, casing was crumbling as it was all coroded.
Had to pull the pins out 1 at a time before trying to unplug it. One pin snapped in half but got that all fixed up, was certain that this was the problem.
Drove for a while thought it was all fixed but then it happened again

Am i not reseting it properly, is there something else i have to do?

Thanks for the advice khal, i think I'm on the right track now.
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1981 924 turbo (daily driver)

elitejaso · Joined: 24 Jul 2007 Posts: 143 Location: Melbourne

Ok managed to unplug and reseat the connection to the DITC.
But still the car backfires on warmup and eventually the tach flop of death.

Never had this problem before i had the engine out to fix the gasket, just wondering what my next steps shuld b to try and fix this problem.

Do i have to remove the DITC and pull it apart? really wanna avoid this.
Hoping its something simple but that just doesnt look to be the case anymore.

Ideas or any direction on what to try next would be greatly appreciated.
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1981 924 turbo (daily driver)

Smoothie · Posted: Wed Dec 02, 2009 9:50 pm Post subject:

Also try an unplug-replug of the ignition trigger (on the front-left wheelwell, connector/s near the coil, and the crank sensor connector at the DITC box.
Shouldn't be a need to disassemble the DITC box (though they sometimes come apart with rough handling of the connectors).

Are you having unusual moisure/humidity problems there lately?

Of course if there happens to be water dripping onto the DITC box, then disassemble to dry it out..
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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

elitejaso · Joined: 24 Jul 2007 Posts: 143 Location: Melbourne

Thanks for the reply smoothie,
Did everything you recommended but once the car got warm again it start to sputter untill it died (tach flop).

There also was no water dripping or around the ditc box so dont think its stuffed.
Was talking to someone and they said maybe the engine temp sensor is stuffed/ out of range. Which may have happened a while ago when the car got hot and the gasket blew.
Would a stuffed temp sensor throw my comp out of wack like it is?
Rang porsche and they couldnt help us out with the part.

Anyone got a working temp sensor for an 81 932?
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1981 924 turbo (daily driver)

Smoothie · Posted: Thu Dec 03, 2009 12:35 pm Post subject:

A bad intake air temp sensor wouldn't cause tach flopping and backfires.
It'd only affect ignition timing, causing that to be either too advanced or too retarded.

Might the crank sensor and/or its' wire have been damaged during the engine pull/replace?
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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

elitejaso · Joined: 24 Jul 2007 Posts: 143 Location: Melbourne

crank sensor and all the wires check out. Decided to check out the wur and found out that im missing a vacuum hose i think, just under the electrical connector to the wur. But cant seem to figure out where its meant to go. Any ideas?
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1981 924 turbo (daily driver)

9xx · Joined: 18 Jun 2006 Posts: 627 Location: Jarvenpaa, Finland

elitejaso · Joined: 24 Jul 2007 Posts: 143 Location: Melbourne

elitejaso · Joined: 24 Jul 2007 Posts: 143 Location: Melbourne

Ok cars still not running,

had a brief chat with someone who used to work on these cars and he said that what i was describing sounded like a dodgy temperature sender.
Said that after the engines overheat that these things can go out of range.

So i pulled the dizzy out got the clip off that goes to the sender and realized that one of the wires in the connector was damaged at some point and there was no way that this connector was working, so i fixed that up hoping that this was the cause of my problem.

Also had the temp sender out tested it with the multimeter and it checked out (doesnt mean it could still be fried internally though).
A new one is gonna cost me $170 so i decided to clean it up and put it in hoping that the connector was the problem.

Put it all back together and same BS!!!
Before forking the money for a new temp sender was just wondering if this could be casusing my problem anyway.
Could someone please explain to me what this sender exactly does and how it affects the running of my car.

Thanks in advance guys
Jason
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1981 924 turbo (daily driver)

Smoothie · Posted: Sun Dec 13, 2009 10:55 pm Post subject: Re: Loosing my cool

There are 5 temperature sensing devices. Two of them are in the area where you were looking at the rear of the head - the temp sender for the dash gauge, and the thermo-time switch. The temp sender's only attached to the gauge and has no affect on the running of the engine. The TTS only has an affect during starting (if the engine (and the TTS) are cold, it will close its' switch supplying power to the cold start valve, but only while the key is held in the start position). Long story short, neither of them could be causing your problem. Temp sensing devices 3 and 4 are the CSV and WUR. A bad CSV would cause either a too low or too high idle, so that's not the problem. WUR is a possibility as it would cause your A:F mix to be either too lean or too rich if it isn't functioning correctly (at higher temps it should be leaning-out the mix - if it isn't, then it's causing the mix to be too rich after engine warm-up). BTW, the following is apparently referring to the WUR -

924RACR · Posted: Sun Dec 13, 2009 11:14 pm Post subject:

Tach flopping wildly is a symptom of losing the crank signal.

Not a temp sensor out.
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Webmeister
'79 924 #77 SCCA H Prod racecar
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elitejaso · Joined: 24 Jul 2007 Posts: 143 Location: Melbourne

Thanks for the info guys,

It was the thermo time switch that i fixed up then.
Will look into the wur when i get the chance.
Any way to bypass the wur to see if it is causing my problem?
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1981 924 turbo (daily driver)

Paul · Posted: Sun Dec 20, 2009 1:30 am Post subject:

Have you checked your system and control pressures yet?
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