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pockygt

Okay, long story short:

I had to avoid someone by accelerating and accidentally mashed the exposed wires for my DITC (the 12 pin connector, mid-replacement/repair) and I think I may have shorted something together. Right when this happened, the car was stuck idling at about 4000rpms. Pulled over, got the idle down, was fine. Drove home and on the way back, I was getting some TERRIBLE backfiring.

Okay.

Now, The car starts fine. Runs fine too. But once it reaches operating temp, the backfiring from the exhaust and sputtering comes back, floppy tach, etc. It only happens under load really, and is constant, so driving is near impossible.

I have a replacement DITC box, and even O2 control computer. But I don't want to go putting those in, and risk ruining them. I want to make sure that it's the computer itself, and not an f'd up signal from a sensor.

The problem I'm having is as such:

-Is there a sensor signal that could cause this that goes to the DITC?
-What is the wiring for the DITC like? The wiring diagrams in the haynes don't seem to match up with the DITC, and they sure don't call it by name. Does anyone have some good factory manual scans?
-What else could cause this if not the DITC?

I know it's kind of a tall order, but I appreciate any info that can be given.
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1981 924 Turbo (931)

Smoothie · Posted: Thu Mar 20, 2008 12:10 am Post subject:

At top and alone on my suspect list for now would be the 12 pin connector since that's known to cause those symptoms. Normally you'd unplug-replug the whole connector, but since yours is dissasembled, just unplug-replug each pin and be sure each one is tight - close each just slightly with pliers if any are loose.

This should help in verifying the position of each wire -
http://www.flickr.com/photos/9754161@N02/738872385/in/set-72157600685473952/
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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

pockygt · Posted: Thu Mar 20, 2008 12:17 am Post subject:

what I did with the connector was take it apart, solder new terminals on, and then had them plugged in individually. they are clean and plenty tight. i just wish the original connector hadn't crumbled in to pieces when i took it off.

I guess if anyone knows, you do. How does this DITC operate? What can it control other than just spark timing? Sorry about all the questions, I'm just trying to wrap my head around this thing.
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1981 924 Turbo (931)

Smoothie · Posted: Thu Mar 20, 2008 1:19 am Post subject:

All it controls is spark timing (and presumably dwell). It bases its' "decisions" on input from the crank sensor, intake air temperature sensor, engine rpm, and manifold vacuum/pressure. That's about all I know about it. Keep the connections good, don't try to adjust the timing, and there's rarely a problem with them..

If the 12-pin connector, or what's left of it, is ok, then I'd double check the crank sensor connector, wire connections to the coil, and multi-pin connectors near the coil.
If still a problem, obviously try swapping in your other DITC box.
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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

pockygt · Posted: Thu Mar 20, 2008 1:40 am Post subject:

okay. Thanks for the insight. It's nice to know that despite how complicated the system seems, it's not anything that can't be "dealt" with.

I was also worried that the other box could be ruined by being swapped in if there was some sort of lingering short or something. But that's just me being crazy.

Oh, and another question. If the DITC controls timing and dwell, then what is the transistor unit on the fender well for? Just for actually grounding the coil based on what the DITC tells it?
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1981 924 Turbo (931)

Smoothie · Posted: Thu Mar 20, 2008 2:36 am Post subject:

Yeah, DITC signals the unit on the wheel well (aka- the ignition "trigger"), and that fires the coil, and bingo-bango the spark plug sparks..
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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

dpw928 · Joined: 02 Nov 2002 Posts: 1860 Location: owasso, ok 74055

Same thing happened to mine (holder crumbling) and I also made new pins. My problem with this is that the pins are left exposed so humidity and movement can cause problems. My last problem was a loose connection on the green and white wire. This caused the engine to miss fire.

Dennis
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81 931 5 sp
78 928 5 sp Silver
78 928 AT Euro Black