Herbie

My ignition switch, after 1 half hour, warms up, and extracting the key, it's hot.

Is it a weared switch? My key isn't heavy, but previous owner travelled for 125000 km.

Can I fix it with a simple contact cleaner in the hole, or is it a unfixable problem ?

Thank you

964Cab

Adrian, et al.

I tried just the key itself with no other keys on the key ring and the problem still continues. Is it your impression that the DME Relays sole purpose is to turn on and off the fuel pump and to also supply + volts to the DME "brain". I'm on my 3rd DME relay.

Question, as a test, how could I bypass the entire "central electrics" to see if my engine would run normal with no sudden loss of high voltage to all 12 plugs at once in an intermittent fashion ?

As you know I've already hot-wired the twoignition coils through a kill sw and the result was no more XMAS Tree effect. Wonder what would happen if I bypassed the entire central electronics ? Does the DMe "brain" need any other data from the central electrics other than the DMe relay data ?

If I can force the DMe relay to provide +volts to both the fuel pump and DME "brain" what else would I have to bypass ? I am soon going to change the ignition coils as well as their companion ignition "ignitors" and I have a Hammer appt next week. But if that fails to provide a fix I would like to bypass as much electrics as possible to narrow down the problem.

Thanks,

Patrick

PS: As you noted the ignition lock has many layers. The layer just prior to the starter layer is the layer which I suspect is my problem, but not at the key lock itself but rather down stream further.

Adrian

Herbie First,
Depends what you call hot. Yes it should be warm and lot of current flows through the different sections of the ignition switch. Should it be very hot, no it shouldn´t.
I very much doubt that there is anything wrong with your system Herbie,
Ciao,
Adrian.
911C4

Adrian

Dear Patrick,
What you are looking to do is not only radical but very risky. You can hotwire the DME direct and bypass the relay. You have the diagrams.
I think you need to follow the wiring from the DME connector to the igntion coils. Power off and use an insulation tester. Sounds to be like you have a chaffed wire. Seeing as you are not blowing fuses it may be an earth problem.
I would as already suggested lift up the central electric. This is an easy job (disconnect battery) and check underneath. I know of a few cases of corrosion (major) being found under the central electic. Broken wires as well. I would certainly concentrate on relay R41 and its socket. DME relay. Damaged wiring is not uncommon. Replacing the relay actually tends to mask the problem. Disturbs the wiring and it seems to work for a while.
No maybe you are actually damaging these relays. A high current draw fuel pump will damage the relay contacts.
I do not recommend you attempt the radical bypass idea. I would hate to see you cause more damage. This can get costly. You could run a dummy cable between the DME and the coils. Only attempt this if you can open the DME connector and remove the wires and pop in a correctly pinned dummy wire. Do not attempt to jam things in or splice.
Ciao,
Adrian
911C4

964Cab

Adrian: For some unexplained reason my car runs fine IF I take the rear blower motor out !!!!!!

A little history. I bought this C4 in April 2001. At the time I had no heat nor A/C and at the time found the rear blower motor fuse blown. In April 2001 I took the CCU out and found a RED wire to the CCU that was shaved, perhaps by a prior tech for some unkown reason ? I placed electrical tape over it. I replaced the rear blower resistor and fuse. Now I have heat but still no A/C. But how does having the rear blower motor in the system affect the ignition operation ? I should also note that the prior owner's repair bills reveal a new rear blower motor was installed. So it looks like this car has a long history of heater related problems but how could heater related issues influence the ignition system ?

Thanks,

Patrick

Adrian

Dear Patrick,
I answered this question on your email I received from you. However for others, here is the answer.
The Rear Blower motor operation is partially controlled by the Aircon/Heating control unit. This same control unit feeds data to the DME. If the rear blower fan is taking the controller out, the controller will also take the DME out. The temp control setting is feed directly to the DME. This same signal is used to turn the blower fan on to low speed.
Also the rear blower fan if running at a too high current load will load the electrical system down and this upsets the DME no end as well. I suspect a failed blower fan sucking the electrics down first. This will also give you the XMAS tree effect as well. The sudden loss of power I would say may well be the alternator stalling under the load. That little alternator can stall your engine very quickly when it locks up.
Obviously this is not a full technical breakdown but the simple explanation. 964 owners need to understand that everything (well almost everything) is somehow related or interfaced with everything else.
Ciao,
Adrian
911C4

PS: You should see what is taken out when you have a power window regulator motor short out. The power is tapped off for anumber of other circuits as well. This is very common in the 964.

964Cab

Hi all,

At last, I fixed the freaking thing !!!!
Today in the mail I got my two new Bosch ignition coils and their companion set of Bosch ignition ignitors. The ignition coil bracket was a little tricky to loosen up so I could get the old coils out (4mm Allen). The ignition ignitors were easy to install and I put that special heat paste on their rear-ends as per instuctions.

I did away with the hot-wire (kill sw) that I had installed and with a deep breath started the 964 up, it was from a cold start, as the
instuctions say to install new ignition ignitors only on a cold engine, so the car started with a ROAR !!!!! The idle was instant 1000rpm and settled to rock steady 800rpm in a few minutes.

I drove the car for 20 miles and it felt like a new car, the engine was firing
perfect with no problems, no XMAS Tree and no intermittent Cab light fault (in the clock) as well.

The problem I fixed with the new coils and ignitors was an intermittent sudden lose of all 12 plugs and if at hiway speeds the
car would restart itself with a dramatic jerking motion and if at idle the car would just suddendly die. It could always be restarted however.

The car must have been trying to run on just the primary or secondary ignition system ? Now that the car is fixed; when I put the shifter in neutral on the hiway the rpm drops directly to 800rpm and doesn't any longer drop to 300rpm and then hunt it's way back to 800rpm. So my car must have been trying to perform on just 6 plugs and the DME "brain"
must have been cutting the engine off ? Or perhaps the problematic secondary or primary ignition system was just intermittently dying ?

Whatever the cause the problem is now GONE !!!!!!

Thanks,

Patrick

Arjan B.

Hello John,
Here in The Netherlands we have most of the time rain, and now it's winter.
I have a new Dme Relays in my 964 C2 [1992], but when it freezes outside, sometimes when I start the car, no step on the gas, the engine goes off.
Starting for the second time works, and the engine keeps running after that.
May be it's that fuel needs some heat to mix with air for a good 1:15kg fuel mix.
Cold metal is bad for cold start, so fuel stucks on the cold metal and thats why you need more fuel for a cold start. Motronic does this automaticly by Motronic computer.

May be it helps a little to clean the Idle control motor [ leerlauf Fullungs Motor ]placed
on top of your engine in the middle, just lon the left of your air filter/intake control. [silver couloured with two hoses of rubber on it.]Sometimes they will be slow on reaction by dirt, Carbon dubris from the engine ventilation system.This thing controlls your 900>950 rpm thing, and stabilizes your engine after start.[start>High,low,little high, little low, stabile, 900rpm.]
General Motors {Opel in Europe} use the same one for their cars, so i know the problem we had with those things.[I am a Chief Mechanic in a Gm Dealership]

Hope this helps,
Don't worry,
Arjan