Peter,

I had a similar situation on an '88. The output of the LH to the injectors is two wires on one connector pin to the LH. One wire was crimped too tight breaking all the strands in the wire. It ran on 4 cylinders destroying the thrust bearing and the drive shaft. The connector is the one that plugs onto the LH. Take the cover off of the connector to check the wires. There is no flex on these wires when the cover is on, so I figured it was a factory defect.

 

Well, it sounds like this has been resolved. I'm going to have to borrow a final stage for my car and see if that cures the problem I have. The symptoms sound very familiar, and I've replaced all the plugs, wires, and injectors. Had the caps and rotors cleaned and checked for tightness, they look fine. Last things on my list are a coil to swap and the ignition final stage.

Thanks for the info on this, I'll let you know what I find on my car.

 

Thanks Earl,

is it difficult to open this plug to the LH, any watchout things doing it?
John, I will recheck the ground points under the throttle wire wheel at the rear.
(I think I have done that two Years ago when refurbishing the intake)
But this does not explain why my fuel pressure drops when engine heats up?

Thanks again all, your inputs are highly appreciated

/Peter

 

Update:
Found tonight a broken shield to the hall sensor.
A previous owner had cut the cable to the hall sensor in order to make a TB change easier I guess.
I unwrapped the tape around the splice and the shield had been soldered together but had separated.
I have now soldered it together again, seems to go to EZK plug pin number 4.
Not sure if this could have anything with my intermittent cut out to do or not?
Test drive tomorrow will tell

/Peter

 

Ok,
take a look at the picture below, what you see is the broken shield on the cable to the hall sensor.
A previous owner cut the cable doing a TB change I guess.
When I bought the car I changed the TB and waterpump and soldered the cables together again.
When unwrapping the isolation tape that I put on there after it turned out that the shield had separated again.

So my conclusion is that the major reason (maybe only) for the cut outs that I experinced was due to this.
The car now has a power and punch that i have never experienced before.
Above 4K it is awesome
Thanks to all who helped, the final solution came when a fellow 928 owner here in Sweden told me that his BMW behaved just like my car and the fault was the hall sensor.
I still have a fuel pressure that sometimes drops when engine is fully warm so the FPR will be replaced, hopefully that is the end to problems i have had.

Thanks again/Peter

 

Glad you found it. I never know the Hall sensor had that dramatic of an effect on the car. This is going into my archives.

 

Broken Hall sensor retards timing 6 degrees. I suppose if it was cutting in and out, that could cause some weird behavior, but most people are not aware of a broken Hall sensor unless they have a very sensitive seat-of-the-pants power meter.

 

Hello Peter
OK, good !

As Bill says the absence of the Hall signal will not affect normal running only high load/ medium to high rpm conditions where it retards the igntion by 6 degrees It would not cause the type of cutouts you experienced.

I think these cutouts must have been caused by electrical noise picked up on the broken screen and fed into the EZK which upset the igntion circuits. The EZK is very sensitive to interference.

Didn't the Spanner register a Hall sensor fault code ?

 

What i experienced was definitely not 6 degrees retard, more like 180 degress .
John I think you are right the open shield confused the ignition system and caused the cut out's.(it was like power on and off with high frequency)
I read some where that the shield also carries some signal back to the computers.
With the total break that was of course not possible.
No fault codes with the spanner which made this hard to trace.
I did also replace my ignition stages but and the car seemed to improve but still had issues with sudden cut outs, maybe not as frequent as before.
When i fixed the hall sensor cable it had a slight hunting at idle.
I did a battery reset for 10 minutes and took it for another spin and it started to run better and better, hunting is now gone as well.

/Peter

 

OK Peter, fingers crossed !

 

Issues with the Hall Sensor circuit (whether then sensor itself, the connector, or the wiring) can have a wide spectrum of effect on the car. I don't know why. We all know what 'the book' says. But, there is direct experience that the effect can be either an unnoticeable-without-the-hammer fault, a total lack of top end power (my '89) or cutouts and stumbling with an eventual no-running end-point. The latter effect has been reported at least twice on this forum (this thread and Doc Mohr) and also occurred recently with a local-to-me non-forum-visitor 928 owner after a right-side cam cover reseal (which resulted in a damaged Hall sensor connector.)

I support John's speculation about noise on the circuit due to broken shielding. I'd love to know, though, what the EZK thinks its doing.

 

Well crap!

I think this just happened to me yesterday. I was just driving along and while going down a hill at 35MPH I was using the engine to "brake" my speed. All of a sudden the exhaust note changed. WTF? I got to the bottom of the hill and the car began to run like crap! No power at all. Managed to pull over - idle was barely holding 400RPM! I was hesitant to shut it off in case it wouldn't restart, but I did it anyway.

Upon restart everything was fine. I was in my work clothes, otherwise I would have started pulling stuff off to investigate. But it seems fine now.

One addition to this story. Shortly before this happened, I took a co-worker out for a hot lap around our office building. I saw him clench his but cheeks and do a leg-press as we hit the corner. When the engine cutout later (about 15min) I noticed the WB O2 sensor was giving me an error. The last time that happened I found the a passenger had pushed so hard on the floor that it pinched the ground for my WBO2... anyway, just thought I would share. I'll report if I find anything substantive.

 

Hmmm.... sounds like the SC cars need another part in the kit: a reinforced CE panel cover.

It has always bothered me that there isn't more protection for the central electrics. Not just the panel. The LH and EZK are covered only by the hump of carpet-covered foam. One swift kick in the ECUs and...