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Rob the plumber
Joined: 25 Aug 2008
Posts: 122
Location: Utica, Michigan
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 Posted: Fri Sep 19, 2008 11:39 pm Post subject: Car died??? |
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I got in my 931 this morning and went down the road. It popped from the exhaust a couple times. I pulled into a parking lot to check it out and the engine died. It would not start back up either. I sat in the car for five minutes or so, and tried to start it again. It fired right up and seems to be running fine.
I am guessing that it is an ignition problem considering it backfired through the exhaust.
Any input, or common things to check?
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Maybe924
Joined: 14 Aug 2007
Posts: 412
Location: New London, CT
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| Posted: Sat Sep 20, 2008 12:40 am Post subject: |
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You probably have a vacuum leak. Its causing you to lose boost and also causing your backfiring. If its large enough it can keep the car from starting.
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1981 931 GT (CGT Intercooled)
1985 911 Targa Carrera (Sold) |
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Rob the plumber
Joined: 25 Aug 2008
Posts: 122
Location: Utica, Michigan
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| Posted: Sat Sep 20, 2008 10:19 am Post subject: |
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What is strange is that it has been running fine all day. I have driven it about 70 miles.
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Rob the plumber
Joined: 25 Aug 2008
Posts: 122
Location: Utica, Michigan
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| Posted: Sat Sep 20, 2008 1:58 pm Post subject: |
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It did it again. The problem happens after a cold start. The car starts fine and drives fine for about 3 minutes. Then it pops through the exhaust no matter where the gas pedal is at, rather randomly. It will stall if I don't pump the pedal. After a minute, it runs fine.
I noticed that when the engine misfires, the tachometer drops to zero. I remember this being a sign on my old 4.0L Jeeps that the crankshaft position sensor, or the coil was bad. (The CPS provides a signal for ignition timing. No ignition, no tachometer)
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Maybe924
Joined: 14 Aug 2007
Posts: 412
Location: New London, CT
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| Posted: Sat Sep 20, 2008 3:23 pm Post subject: |
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Does the tach bounce at all? Have you checked voltage at the battery with the car running? Perhaps you have a faulty alternator putting out too much or too little voltage and causing a bit of havoc with your DITC?
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1981 931 GT (CGT Intercooled)
1985 911 Targa Carrera (Sold) |
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ideola
Joined: 01 Oct 2004
Posts: 15550
Location: Spring Lake MI
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| Posted: Sat Sep 20, 2008 4:14 pm Post subject: |
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Also worth investigating whether the big connecter thingy needs to be re-seated on the under-dash DITC unit.
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erstwhile owner of just about every 924 variant ever made |
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Rob the plumber
Joined: 25 Aug 2008
Posts: 122
Location: Utica, Michigan
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| Posted: Sat Sep 20, 2008 10:29 pm Post subject: |
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DITC???? 
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ideola
Joined: 01 Oct 2004
Posts: 15550
Location: Spring Lake MI
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| Posted: Sat Sep 20, 2008 10:39 pm Post subject: |
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Digital Ignition Timing Control.
From this thread: http://www.924board.org/viewtopic.php?p=211145#211145
| Smoothie wrote: | It might be as simple as a bad connection at the DITC box. An unplug-replug of the rectangular 12-pin connector normally fixes this for a while. -This used to fix it for 6 months to a year for me. Since the time I disassembled the connector and -slightly- closed each female terminal with pliers, it hasn't happened again.
A key symptom of the connector problem is the tachometer needle will flop around, out of time with the engine speed, along with popping, backfiring, no power, etc.. This problem is also moisture-related and is more likely to occur on a rainy/humid day. |
There are several threads on this topic, but the Reader's Digest version is that on 1981-1982 931s (i.e. Series II) the DITC box (mounted directly under the steering column) has a large multi-pin connector that tends to work its way loose, and can also be susceptible to moisture (it's been VERY wet in SE Michigan the past several weeks...). When that happens, all sorts of strange and bizarre behavior can occur. If I were you, I would simply disconnect that thing, hit it with some compressed air at both the harness and the DITC (to dry out / move any moisture away), and re-seat it. See if your problem goes away. One of the few cheap and easy fixes on these cars 
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Smoothie
Joined: 01 Jan 2003
Posts: 8032
Location: DE (the one near MD, PA, NJ)
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| Posted: Tue Sep 23, 2008 3:46 am Post subject: |
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Yessir - except for the location...the DITC box is on the center hump behind the radio, next to your right leg for an LHD car. Under the steering column is the lambda (o2 sensor system) control box, ya-all (I just moved a bit south).
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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 |
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ideola
Joined: 01 Oct 2004
Posts: 15550
Location: Spring Lake MI
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| Posted: Tue Sep 23, 2008 4:14 am Post subject: |
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Whoops, sorry about the wrong location info...since I don't have a SII, I didn't have a ready reference...sorry 
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erstwhile owner of just about every 924 variant ever made |
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Rob the plumber
Joined: 25 Aug 2008
Posts: 122
Location: Utica, Michigan
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| Posted: Fri Sep 26, 2008 12:52 am Post subject: |
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What is the banjo fitting on the DITC box for? Manofold pressure for timing retard or something?
I jiggled the electrical connector and it has been fine since.....
thanks!
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924RACR
Joined: 29 Jul 2001
Posts: 9075
Location: Royal Oak, MI, USA
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| Posted: Fri Sep 26, 2008 1:06 am Post subject: |
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Exactly - boost read for timing retard.
The smaller of the two connectors is a 3-pin connector for the flywheel pickup. I have a regular problem with corrosion forming on the contacts on the DITC, usually over the winter. Have to remove the connector and scrape it clean, then it's usually fine for the summer. Otherwise it'll run OK most of the time, but cut out and belch black smoke over bumps. So I'd recommend you remove and inspect/clean the contacts.
Hey, you coming down to check out the races this weekend???
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Vaughan Scott
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'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
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Rob the plumber
Joined: 25 Aug 2008
Posts: 122
Location: Utica, Michigan
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| Posted: Fri Sep 26, 2008 1:20 am Post subject: |
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I would love to check out the races, but I have to work the afternoon shift on Saturday and Sunday. My son would absolutely love it too.
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