Tmistry

Hi all,

I happened to check my ignition coils by disconnecting each and starting with only one. I noticed that with one of the coils, the engine had very poor throttle response and was clearly missing, while with the other, perfectly good. My first thought is to replace the coils. My question is, is this definitively the problem? I assume that the missing could be with the distributer cap or something else like the ignition control modules but is the first step to replace the coils?

Also, is the replacement of the coils just remove and replace simple? Any tricks? Is the Bosch part best or is there an upgrade?

After reading Streather's bit about the dual distributer belt failure, I'm perhaps overly concerned with the ignition system. Any tips are appreciated!

Thanks guys.

Lorenfb

"My first thought is to replace the coils. My question is, is this definitively the problem?"

There're a number of possibilities besides just the coils:
1. ignition modules
2. coil ignition wires
3. distributor caps
4. rotors
5. belt timing of the second distributor

Tmistry

Thanks Lorenfb.

Your list makes sense. Any recommendation on what to replace first? I'm planning to go as follows:

-Ignition Coils
-Ignition Modules
-coil ignition wires (seem fine)
-distributor caps (visual inspection, seem fine)
-rotors (haven't checked, will the integrity of these be visually obvious?)
-belt timing (not sure how to check, will need to take it to my tech)

Make sense?

Vandit

How are you isolating the coils? Disconnecting the ignition lead isn't the proper method to isolate them and can cause the car to not run at all on any single coil. Instead, isolate them by disconnecting the ignition module.

Tmistry

Thanks Vandit. This changes things a bit as I was simply disconnecting the lead wire to each coil. I'll need to re start after disconnecting each ignition module then.

Is the disconnection of the ignition module obvious?

Vandit

I borrowed this pic from another thread, so ignore the red arrow.



You can see the two ignition modules here, you press the metal bar to unlock the connector and pull down to disconnect.

Tmistry

Ok, redid the test removing the plugs at each module with the same result. One was fine, the other resulted in a really bad idle and stall.

Is that conclusive? Vandit, I appreciate the assist.

Is the car ok to drive?

Tmistry

Here's a pic of my coils. Are they original?

An engine pic. Looking better without the blower. Damn that sound pad is a nasty POS to remove. Just awful!

Feudal Serf

Hey Tmistry,
Might turn out to be the ignition coil.
I posted on another thread about a similar problem. My problem turned out to be a poorly seated plug wire on cyl 1. Car had just returned from valve adjustment.

First, if the smooth idle running on one coil happens to be the secondary then that implies the distributer belt is ok. Primary distributer runs off crank secondary off belt from primary.

I would run the car switching the wire from each coil to distributer cap that runs with poor idle. To try and locate the problem to the coil. Careful with the high voltage wires, not to shock yourself.

Problem can be as simple as a bad wire or spark plug. 964 is very sensitive to that.

I had to run the car on the single coil with rough idle and serially pull off wires for each cyl directly off tge distributer. Not while running. Restart and i found that the idle was worse with every wire except cyl 1.

Then i took off catalytic converter to access lower wire and found wire wasnt seated into plug.

Its rare for ignition modules to fail.

Coils apparently are known to fail. I knew my distributer caps, coils and wires are new.

Have you had any recent work done? Valve adj?

My bet is distibuter cap, wire or plug.

Good luck.
FS

Tmistry

Feudal Serf, Thanks for your well reasoned input. Great info on isolating a potential secondary distributor belt issue. I'll run through your suggestions and follow up. No recent work, other than my own replacement if my engine carrier and motor mounts and a ton of miscellaneous stuff. I had the valves adjusted last March, about 3000 miles ago at most. Thanks again!

Vandit

Yea, those are probably stock because they're black. The replacement ones available nowadays are silver.

sc

I just replaced one of mine and it was Bosch black and probably the original. The replacement is indeed silver.

newsboy

You didn't say what your mileage is. Coils are often the cause of electrical problems, Christmas tree, etc... Not hard to replace, and not too expensive. Mine needed replacement at 70,000 miles. Also replaced the distributor drive belt.

Tmistry

Right Newsboy, thx for the prompt.

Car has just over 100,000 and is a 1990. I believe I had new wires put in last year when the valve adjust was done. That was the first trip to my tech.

Is the dual distributor belt change a simple DIY? I might just do caps and rotors now as I root out the issue.

Thx!

Tmistry

Ok, an update:

-replaced coils/ no change.
-replaced ignition modules/ no change.

Have ordered:

-distributor caps/ Bosch
-rotors/ Bosch
-new full set of wires/ Beru

I'll keep plodding on, I suppose! I never noticed the issue until I pulled one ignition module and ran each independent. Ignorance may have been bliss in this case! Can't seem to drive my 964 now without thinking I'm somehow hurting things.

Anyone else have an uneven idle on one distributor and just leave it be?

The bad distributor is the primary, btw. So, it's a relief that the belt isn't the root cause.

Best/
Tim