ckkrause

My original issue was that I had a loping, uneven idle that I wanted to solve. I first replaced the spark plug wires because they were original on a 93K car and there was lots of blue sparking when I watched the wires in the dark. It help a little, but no real change. Through a troubleshooting process I found that the coils, ignition control units, wires, distributor caps and rotors are fine. In that process of elimination, I found that when I pulled off, in turn, the connectors to the Ignition control units. It ran fine with only the right one connected and ran very poorly...missing, backfiring, etc. with only the left connected. So, it appears that the problem has something to do with the wiring to the plugs. I checked the grounds and they have good continuity, and checked the wires that go from connectors to the coils and they also seem OK.

Question: HELPPPP! Anyone have any idea where I go from here? I followed the wiring and it goes through the firewall...to where....

Thanks for your help...please.....

-CKKrause

mojorizing

The wires to the ignition switch units (igniter or final stage) come from the DME.

Have you swapped the connections to these ignition units...the right (forward unit?) with the left (after?) wiring? and the problem still remains but on the other coil/plug wires? You say you've eliminated all of the ignition system, but I think this swap will tell you if there's a problem with the wiring to the DME.

Check the DME under the left seat. I would disconnect the battery if you want to re-seat the connector into the DME.

later, Kevin

ckkrause

If I understand your question, yes. When I unplug one of the ignition contol units and then move the plug from one ignition control unit to the other, so the car is running on just one distributor, it runs fine on the front plug and either coil/distributor, etc... When I use the rear plug and disconnect the front plug, again using only one distributor at a time, it runs like crap....... So, sounds like I should take out the seat and check DME wiring....

Thanks!

-CKKrause

Lorenfb

"So, sounds like I should take out the seat and check DME wiring...."

No!

There's a single DME output. You're not understanding your diagnosis.
Each plug is unique to each coil & thus to each distributor and thus to each
set of plugs, i.e. upper/lower.

dfinnegan

Hmm, I'm a bit confused, too.

I can understand that there is one DME connection. If there is a problem with the DME or the wiring from the DME then there should be trouble with both coils. No change when swapping.

When testing the coils/switches is it acceptable to disconnect, say, the front coil at the plug and then test the rear coil on both distributors?

And, then test both distributors on the front coil?

Or, are you saying that the coils are unique to the distributors so that the front coil, for example, must always be wired to the upper distributor and the rear coil to the lower?

Lorenfb, sorry to be beating on this issue, but I'd like to understand these coil issues a bit better as they seem to be coming up a lot; rightly or wrongly.

Thanks for your patience and understanding and for all of the excellent information you've already provided since I've been hanging around here!

Cheers,
Dave

ckkrause

Loren-

Right, I didn't trust my diagnosis....
If I understand your comment, then the plugs should not be interchangable? When I looked at the wiring diagram, I thought the plugs basically have the same signal source and are basically tied together so they should be able to be used for either coil or either ICU? Not true?If one of the plugs works with both coils and one doesn't, then what do I have? I am perplexed....

-CKKrause

Indycam

A bad plug ? A bad wire between the plug and the dme ?

Lorenfb

How it's wired:

1. Plug determines; the coil (front/rear), the distributor, the ignition wires,
the upper/lower spark plugs
2. The ignition modules are independent variables, i.e. they can be used for
either the upper/lower spark plugs.

Test Procedure:

1. Determine that both modules is O.K. just by using the "good" connector.
2. Determine that each coil is O.K. by switching ALL its leads with the other coil.
3. Determine that each distributor, cap/rotor, plug wires, & spark plugs are
O.K. by switching each coil wire to each distributor.

mojorizing

Following Lorens procedure will narrow the problem down.

The ingnition switch does have the same signal from the DME, but physically where the signals separate, I don't know.

>>>>edit: in the following swap I didn't follow Lorens #2 test<<<<<

I just swapped my ignition switch plug from the primary to the secondary switch leaving the primary switch disconnected and the car started and ran as usual. Visa versa with the secondary to the primary, and the car started and ran fine. In both cases I didn't take the car out for a drive but it sounded fine.

In doing all this I noticed the plugs have male compression type fittings to mate with the female blades in the ignition switch receptacle...inspect the plug for anything funky going on here.

let us know what you find.

dutchcrunch

on sytem that is missing remove wire at cap and check the continuity of that stud along its surface. bosch clear coats the caps and all my studs were clear coated on mine. as the wire is pushed onto the cap on all but one scraped the clear coat away and made a connection , did not notice that when both coils are connected but when i disconnected one at a time one system could not hold idle for long and die. when i ordered my new caps from porsche the cap end had the same thing, used some acetone and a q- tip and removed clear coat on all the studs, car runs perfect on either sytem perfectly. if no ones believes me i will send you the old caps. i bet this is the reason a lot of cars are not running good on either sytsem of course you have bigger problems. you said you replaced the wire it ran a little better, check that cap.

ckkrause

Loren-

So, the one thing I didn't do in my troubleshooting was changing over the two smaller wires when I changed from one coil to another in order to match the ignition control unit with each coil, distributer cap/rotor, etc... as well? I'm going to redo the troubleshooting with this in mind....

Thanks again!!!

-CKKrause

Lorenfb

">>>>edit: in the following swap I didn't follow Lorens #2 test<<<<<"


2. Determine that each coil is O.K. by switching ALL its leads with the other coil.

That's the ONLY way a potentially bad coil can be ELIMINATED as a source of the problem.

ckkrause

Loren-

Thanks!! Got it!! Bad Coil and Spark Plug Wires...... I have my dead steady idle back and I'd forgotten how much smooth power this car had!! Good Stuff!!

Thanks again!

-CKKrause