JPS

And if so, what was the cause?

Also, I know they get hot, but how hot is too hot?

nine9six

Why don't you do some Google searching for failure modes of porsche 993 ignition control modules? Let us know what you find, JPS

JPS

I have been on this board for over 15 years. Of course I have googled, and talked to mechanics. I'm asking people from this board what they specifically have learned.

If you don't want to answer or can't, then you don't have to.

mpruden

Sorry, I can't help you JPS. What I can say is I've tracked my 993 in triple digit ambient temp here in sunny California. Knock on wood, I've not (yet) had a problem with the ignition control module.

nine9six

Thanks for letting me off the hook, JPS! ; )
I appreciate the slack...In the meantime, can you ask one of your mechanic friends, what would put an inordinate amount of electrical load/strain on the ignition control module?

How many have you burned through and in how much time?

Now I can't help but wonder if the ignition control module could be a root, or at least a contributing cause of "random" misfire codes?

https://rennlist.com/forums/993-foru...ms-solved.html

TheOtherEric

If you're really concerned it's an issue, you should get a cheap oscilloscope (e.g. ebay) and follow the test procedure in the Repair Manual. It's super easy. My recollection is that you first test the output signal (probe the wires at the module under the drivers seat), then if it's bad you test the inputs to it (from the DME).

But if you do it, note theres a little error in the Repair Manual that I've written about here a couple times.

JPS

It's in the shop 2.5 hrs away, so self testing is out. In tracking down a consistent loss of power at full throttle only above 4K and only when hot, I've replaced the ignition module a couple of times. It may be bad again, mechanic isn't sure yet. If so, I'm trying to figure out what may be repeatedly killing it.

pp000830

My view is if the ignition control module was bad it wouldn't work at all.

It's a bit of a stretch but at higher RPM a marginal coil could have its spark voltage drop far enough that it has problems igniting the fuel. This was a bigger issue back when coil voltages were under 10K Volts
More likely something else like a leaking or even disconnected Varioram vacuum actuator that only comes into play when its control solenoid opens it to the intake system at higher RPMs
Or a fuel supply issue where the volume pushed through the system is constrained.
This assumes the Motronic ECU is stock and has not been messed with.
Andy

IainM

speaking generally for electronic systems, if it's getting hot, it's handling too much power.By hot I mean, if you can't keep your hand/finger on it. Look further upstream, what is the coil resistance and is it in spec?
Check for damaged wires in cables, is the coil resistance the same when measured at the ignition module connector as at the coil itself? Is there any leakage to chassis on the module-coil wire harness?

Looking at the waveform of the ignition module output on a scope could shine a light on the cause.

Should the ignition module have thermal paste applied to get good heat transfer to the chassis?

TheOtherEric

Granted most wrenches hate screwing around with o-scopes and such, but hey this stuff is in the Repair Manual for a reason. They’d probably prefer to just throw parts at it and cross their fingers, but personally I’d prefer an actual diagnosis.

pp000830

Handheld oscilloscopes run about $100 so using one is not a constraint with too high a threshold.
Hooking one up and interpreting what it is displaying is not that difficult.
Andy

pp000830

+1,
Also, speaking to item #7 If the module is bolted to something that serves the purpose of a heat sink it never hurts to remount it with a little thermal paste, even if originally it was dry mounted.
Andy

Mad993

Jps, I know an old post but wondering if you ever figured out your problem. Thanks

JPS

Updated over here: https://rennlist.com/forums/993-foru...l#post16087374

Brando 993

Hi there community.

I was having all sorts of hesitation with the car and loss of power under load.
The car is 1995 993, C2 with a 97 Varioram conversion to the intake manifold. I noticed on load the car wasn't showing the right power. So I started my search. Brought it to a well established place here in Oakville, Ont.

Checked the following:
ECU - pulled it out went through all the components and it looked fine. Was received the computer was good. The car is equipped with a Steve Wong computer chip which is pretty solid so I figured it wasn't this.
MAFS - Was clean and no issues there
Ignition Coil, Dual - When this was checked they found that only power was going to one of the coils. So both coils got replaced as they are assembled together. Still no change in performance and power. Idle was still off and under load there was a lack of power. Even on start up you can notice the car was a little off. But had no issues starting and running.

The last thing to check was the ignition control module switch. This was the fix!! Finally after 1 month and a few unnecessary diagnostic invoices they had figured it out. Power was converting to both coils, car runs like a dream now.

If you are having similar problems, I would get the coils checked first to see if they are both running correctly and the the ignition control switch. Not sure how to test the ignition control module switch but its located under the drivers seat as most of you know. It is incased however and is in a tough spot. Wish this was the first thing they checked but unfortunately for my wallet it wasn't.

Anyway, i thought Id be doing the Porsche community a disservice if I didn't hop on here and run through this. Please ask me any questions if you are having similar troubles. Think I have enough knowledge now of the situation,

Thanks!

Brando