springer3

Best bet is to locate a shop that has a Bosch Hammer or modern reader that reads our antique DME. You may find a local rennlister that has the PC-based scan tool, or even better, a real Hammer.

Good luck.

darth

It's been a while since I had my caps removed but I'm sure I remember the rotors being offset from one another when I dismantled it so I put it back together the same way. Maybe a previous wrench did it intentionally or is it possible the belt jumped a tooth? I know my deck height has been modified so maybe the timing modification was to compensate for the higher compression? Regardless, I like the performance of my car compared to others I've driven. If I move the secondary to be inline with the primary maybe I'll get even better performance or worse? Refering to the following link I believe it applies to our engines.

"This is in contrast to the multiple sparks produced in the twin plug ignition
systems used by Porsche and others. The effect becomes clearer when you consider that at a 1000
RPMs an engine rotates 6 degrees every millisecond. So for every additional spark pulse which is
delayed a millisecond after the first, the piston has moved 6 degrees. Furthermore, the complete
combustion process occurs within 2 milliseconds of the initial ignition spark and the initial spark
burn time can last a millisecond. "

http://www.systemsc.com/technical.htm

Bill

Indycam

The rotors are offset , the caps are also .
https://rennlist.com/forums/964-foru...-question.html
The rotors do not set the timing of the spark .
The computer sends a signal to the coil via the ignition switch / transistor that is mounted just in front of the coils .
All the rotors do is to connect the coil to the spark plug .

Indycam

I would love to come and show you in person , hint hint .

I use a battery operated timing light .
http://www.flamingriver.com/index.cf...d=67/prd67.htm
Its safe and easy .
But it does not show if the spark is big and blue
or yellow and small .

If your motor dies and you clamp this tool onto a coil wire and crank over the motor , if the light flashes , you have one spark . If you then clamp it onto the other coil wire and it flashes while you crank over the motor , you have two sparks .

You can use a spark plug at the end of the coil wire to check for spark but thats a bit hard single handed and if you have never done it before , its a bit shocking .

StanUK951

OK Thanks guys. I ordered 2 new coils, 2 dist caps and 2 rotor arms this morning. I've stripped everything down ready to fit the coils when I pick them up later so fingers crossed.

I tried running the car on each coil - no big differences but it seemed rougher on one slightly, maybe... I had the car running normally, i.e. 2 coils, for a bit and I could definitely detect some missing, every so often it would drop revs and you could feel the lumpiness through the body. If it is something electrical breaking down I think it's getting worse - which I'm pleased about because then I can fix the bl**dy thing!

Also had a look under the central electric unit at the front for any dodgy wiring. The alarm is wired in there but it all looks very neat. I took the tape off a couple of connections and they are all soldered and not loose - couldn't work out if they were actually connected to the DME though with all the wires and tight access.

I wont get a chance to finish the job today, but I will tomorrow and I'll let you know how it goes - thanks.

klr10

Check your main battery feeds. I remember someone had a loose ground cable to the engine which caused this problem. I seem to recall they're not all easy to see...

StanUK951

Springer: The dealer had the car on the hammer to call up faults but said nothing was coming up, I assume because the fault wasnt happening at the time...?

Well, I fitted 2 new coils and 1 dist car and rotor arm! The lower screw on the lower cap was slightly rounded off and seemingly welded in place and being in the most awkward place I couldnt get a screwdriver on it square and I was making it worse - so I've left it until I find a better sized screwdriver or I'll get Jaz (the specialist I take my car to) to do it when I go back for the suspension to be set up...! Why is it always the last screw/bolt/nut in the most difficult place that is seized or rounded off?

Been on two test drives and everything is ok. Subjectively it feels like it picks up slightly better from low revs and so far no repeat of the misfire... The dist cap and arm I managed to get off didnt look too great so I'm glad I did those too.

It will be a long time before I get my confidence back in the car and am not shatting myself everytime I'm at a awkward junction or in a tunnel praying for it not to break down but thanks to everyone for their advice. Hopefully it will save me Indycam's airfare! Fingers crossed!

Indycam

The computer stores the faults .
If you plug in a fault reader , the computer will tell the fault reader what faults it has in its memory .

StanUK951

Hmmm, sure they told me they had the hammer on it and nothing was coming up... Would the faults be stored even if the battery is disconnected (such as I did this weekend to fit the coils) or is it stored until it is cleared by a tech?

Millemiglia

AFAIK the error codes does not clear when you disconnect the battery,
you can reset the DME that way but that would be another post...

Indycam

Not every problem is seen by the computer .
The car can break in a lot of ways and the computer will have no code for them .

mshobe

One more vote for trying the simple fix mentioned in the TSB. I had very similar problems and this fix resolved them completely; I was running on brand new distributors, a fresh battery, and the updated DME relay and nothing fixed the issue until that harness got ziptied and tightened in place. Problem 100% solved.

mshobe

One more vote for trying the simple fix mentioned in the TSB. I had very similar problems and this fix resolved them completely; I was running on brand new distributors, a fresh battery, and the updated DME relay and nothing fixed the issue until that harness got ziptied and tightened in place. Problem 100% solved.

springer3

My recollection is that all codes except the airbag are cleared when the DME is powered down. I think the codes were lost, but surely they would be back after the first drive with the problems noted.

StanUK951

Well, the dreaded misfire hasn't gone away... Got the car back from Jaz on Friday after having the lower dizzy cap changed (which I couldnt remove) and I decided while it was there to get the fuel injectors cleaned as well. The car felt fantastic on the way home, really smooth and quick (the report showed 2 injectors were a bit low so I was really hoping the new coils, dist caps, rotor arms and injector clean up would banish the misfire). However, out with the car again yesterday and it was back, lost power and revs, etc. etc.

I am starting to wonder if it is linked to moisture/condensation... I had literally just washed the car and the first time it misfired was also after washing. Two other times were early morning where the air may have been damp or it may have rained in the night (cant remember if it actually did or not) and the night I broke down on the way home it had been raining heavily too... I have the caps fitted to coils properly so maybe the HT leads are breaking down...

Jaz have suggested it could be the oxygen sensor on the decat pipe (which is a non-porsche part apparently - the sensor not the pipe) or the cylinder head temperature sensor. I am going to try spraying a water mist over the engine tonight and see if I can see any arcing. The hammer revealed nothing in the way of faults recorded. I will also try the TSB if I can work out how to get the back part of the airbox off. I will keep the forum updated on my 'progress' or lack thereof...