giddyupp

Instead of replacing and testing one item at a time I decided to go ahead and install all the spare pieces I had (all used) Green Wire, Distributor, Cap & Rotor. I fired it up and to my amazement it seemed to be much better. Timing mark is still moving slightly but way better. I then proceeded to put back each of my original items one at a time to see if I could get the issue to come back. I have no idea why but it seems as though the distributor is indeed the issue. Thing im really confused about is why did it not fix the issue the first time I switched it ? The only other thing that is different now, is that I have also tightened the timing belt. Here is a quick video of how the marks look now. Should the mark be perfectly stable ?

Mrmerlin

That second video looks a lot like many of the other 928s i have had a timing lamp on,
Drive the car and report your results

Mark Anderson

BTW I know i sent you a used one to test but I have one new distributor in stock for $195

giddyupp

I will take it. I will send you an email shortly with a few other items I need. Thanks again for all you help on this Mark.

Gofishracing

I once had a jumping timing light. It was an elongated hole for the set pin on the Crank Pulley.

dr bob

That's a gift at that price. Glad it's going to a needy owner.

giddyupp

Update: Have now installed the brand new Distributor (thanks Mark). But still having the same problem. Also tried the new spark plug wire without a resistor - made no difference.

To Recap.
Fuel Pressures all within spec
Fuel Distributor and WUR - sent out for testing - All good
Replaced with new: Plugs, leads, Cap, Rotor, Spark Distributor
Replaced coil and TSZ with an older used unit - (made no difference)
Green wire appears to be new (was already on the car when I bought it)
Replaced all vacuum lines

So only things not replaced with new - Coil, Green Wire, Resistors and TSZ.

Just not sure where to turn next, what else is there?

Did changing the spark plug wire for one without a resistor tell us anything ? Im still unclear what that test was for.

Mrmerlin

how does the car drive?

giddyupp

Really rough from cold start. Once its warm it drives much better though there is a definite yet small hesitation while under light throttle up to about 2500/3000 rpm, then it seems to smooth out an go well. If I drive it hard, the car seems to drive great and I do not feel any hesitation from stand still all the way through the rev range - pulls strong.

Mrmerlin

Please check if your wires are arcing in a dark garage also check the firing order of the plug wires on the cap

rjtw

I just ran across and read through this thread. Very frustrating! If the fuel pressures are all fine and we assume that air/fuel ratio is good (is that a valid assumption?)... and with a new spark unit and distributor, and with ok resistors then we eliminate those... and you said new vacuum lines (are we positive there are no leaks anywhere?)... then I’m left with two ideas. Take with a grain of salt.

One: is it possible that there is some mechanical slop in the system causing some bouncing in the spark? The effect of harmonics and load might explain what you’re seeing. You also mentioned some unevenness in the belt tracking, that is never a good thing! A worn key groove at the crank was mentioned above, as were sticky bearings in the belt system. A loose or maybe cracked cam gear on the driver’s side (distributor side) comes to mind as well. A full water pump/timing belt job and inspection of especially the cam gears and distributor drive gears might not be a bad idea. It sounds like you’re due for this anyway.

Two: How does your engine compartment harness look? It connects the spark unit with the green wire, coil and resistors, among other things. Could a bad harness cause the observed symptoms? Have you cleaned the grounds especially on this harness (two major ground points at the front of engine compartment)? In addition you can use a little de-oxit on all these connections (coil, resistors, green wire connection on both ends, grounds), inspect and clean them all if you haven’t already.

As was said above, grasping at straws, hope this is at least food for thought. Hopefully it’s just reversed wires like Stan mentioned (trust him more than me!!) Good luck.

Rick

giddyupp

Replacing all the old wires with new has not changed anything. I will double check the firing order and report back.


As far as the air/fuel ratio goes - im not sure if that is correct. I do know it passed CA smog test, so it seems it should be at least in the right ball park.
The engine harness that runs down the front fender appears in very good shape. The one that runs from the 14pin connector down the front of the engine is not so great. A couple of areas where the outer plastic has cracked with pieces broken away. The wires within this appear to be all very good but obviously without stripping more of the outer casing, its difficult to know whats going on inside. I think the Green wire and TSZ take power before the 14pin. Are there any items that connect after the 14pin that could have an effect on running ?

Thanks again to everyone for all the ideas and help.

hacker-pschorr

Late to this thread but the first thing I do when diagnosing any problem with a CIS or L-Jet 928 is replace the green wire. You cannot tell if they "look" good.

It's the lifeblood of the ignition system, I also try to route mine as far away from any ignition leads as possible.

What spark plugs are in the car?

rjtw

Agreed on green wire, OP stated he replaced it with a used one. Which may also be bad...

Mrmerlin

well I missed that part where the green wire was replaced with a used one.
This one corner you should not cut.