SeanR

That, and people using cheap E-bay parts as replacements. That 951 was one of those. He put new parts on himself and the issue remained so I took a few days diagnosing everything else until I decided to put new reference sensors on anyway. He wasn't happy with the bill.

DR

Hi Sean,

I would think that would have been a tricky one to figure out, especially with the new parts on board, kudos to you!

Cheers,

Dave

docmirror

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Luis A.

Ok so what I hear Dave and Sean saying is that:

a) The CPS is not my current no start problem since I have spark when cranking. My reply: Since I'm almost there in terms of replacing it and I have a CPS coming, I will replace. But I should look elsewhere for my no-start condition cause.

b) The knock sensor needs replacing. My reply to this: Since I'm not doing intake R&R now, just fix the connector and re-sheath the cable will not be a liability, correct? Just to get the car running again until winter . Can a bad knock sensor prevent the car from running? I understand I may get knock if it's a bad sensor but I will likely hear that, correct? Or should I somehow diagnose if the knock sensor is bad and thus be forced into an intake R&R right now.

c) The ticking sound are the injectors firing inappropriately and your LH needs fixing. My reply: If this definitive then I won't bother with testing a different one in the car. Or is there any other diagnosis I can do of the LH specifically before I ship it out, short of trying a known good one. I will do that once I mend the knock sensor (if the brain trust agrees that's feasible). You recommended the outfit in England. I see there is one Arizona. Any reason to send it overseas vs. using the one in AZ?

EDIT: Will do the additional diagnostics suggested by Docmirror with the noid light, which I already have. Thanks Doc.

How does this plan of action sound? Thank you all!!

DR

Jim C is in Washington State and is the US agent for JDS (John Speake) rebuilds. makes it easier to order in the US through Jim, plus for all he has done for the community he deserves our support.

Cheers,

Dave

Taguid

I got my JDS from Louis Ott and it took 4 days as I shipped him mine first. https://www.performance928.com/home.html

DR

I mistakenly thought Jim had picked up selling the JDS stuff from Louis, but I was wrong Louis is still doing it, as mentioned above ^^^ Can't go wrong there for sure!!

Cheers,

Dave

SeanR

I'm pretty sure Roger keeps them in stock also from JDS. Those are the only ones I'll use or install.

FredR

The subject of LH failure is quite interesting. LH failure is [was] very common over here. The unit in my late 90 S4 failed sometime around 2002. Its replacement came from an imported US GT of the same vintage that got totalled. I swapped the chip set not knowing a the time if there was any difference and then used the same unit to install my PEMS when ST2 came along a year or two later. Same LH unit is still powering the car today and I have the original GTS LH/EZ units to put in the car if the current ones fail albeit they do not have PEMs in them.. If the hot climate was a factor I recon the unit I am currently using would have failed long since so in the end I figured it was a random type of thing wherein some die young and others just keep on going.

Obviously tile failure is a common problem and if one unit fails it will be on its way to the UK in hours for JDS to work his magic on. I also have a third LH/EZ unit wherein the LH has failed so might send that off one of these days as a preemptive measure that or stick a PEM in the GTS LH unit as I cannot run a stock LH given the 30lb Design 2 4 hole injectors I purchased at the time I converted to ST2. At least I know I have a workaround if the current LH fails and a good spare to have in the garage.

The EZ units seem very reliable- never heard of one failing so the interesting question is does the LH not have the same reliability given they were both made by Bosch?

Landseer

You know, the LJETs were also deemed bulletproof, but that's no longer the case as their components have aged. Just sayin. So whereas EZK isn't known to fail, those of us like you that have dabbled here a while have been privy to seeing parts slip into the latter part of their lifecycle. Another example is battery ground cable. I had one of the earliest recognized failures back at 2010 frenzy. It' since become a well recognized point of weakness.

DR

Hi Landseer,
Are you sure you have your year right?? Maybe 2000 or 1999? We have always sold battery Ground straps because of fraying and decay, lots of them over the years.

Regardless, it is a good reminder to bring up again, and again! Same goes for the engine ground strap, and coil ground straps. We consider them long term maintenance items.

Hope you are having a great evening,

Dave

Landseer

Ouch. Schooled I am!

And a legend in my own mind.

Glad you are back posting, btw.

DR

OOOOH Snap, sorry about that :-)

No worries man, you are a Legend here already and you don't need no stink'n ground cable to be one!!

Thank you sir, It is great to feel like being here for a change!!

Happy Hump day to you,

Dave

Luis A.

Alright so here is the rest of the story... Sent out the LH ECU to Lou at Ott's Performance Engineering to exchange it for one rebuilt by JDS. As readers of this thread might recall, my failure mode went from being very intermittent and infrequent to finally completely preventing the car from starting. When Lou received it he tested it by installing it on his 928 and reported to me the car started... !!! This is very unsatisfying. I had him exchange the ECU anyway and I received it from him with a quick turnaround. I installed a week ago and the car immediately started and idled perfectly. I have now driven it around 125 miles with maybe 15-20 starts. No failure to start or any other weirdness. It also seems to me that the shifting into reverse from park is smooth whereas before it clunked into R. I recall reading in a thread that this might be an issue with the LH relative to its idle modulation function when shifting.

I mentioned earlier in the thread that I would be replacing the CPS but I have not yet. I repaired the knock sensor connector I suspect it is dead as i measure infinite resistance (open) on it. I do not perceive any knocking under the conditions that might elicit it. I a running 93 octane gas. These sensors will be replaced when I undertake the intake refresh during the cold months.

It's still puzzling to me and deeply dissatisfying from a troubleshooting perspective that the LH worked on Lou's car. How can this be...? Maybe It's not the LH on my car and whatever caused it will surface again? We'll see. Thanks everyone for your assistance and I'll continue to report if anything changes.

FredR

You had a problem, you replaced your LH with a refurbed unit, the problem disappears with the revamped unit and you are not happy with the result? It is not beyond the realms of imagination that the shipping process might just have banged the unit around sufficiently to cause a temporary cessation of the problem once the unit arrived with Louie. Equally it is highly probable that if he took the car for a spin the first pothole might cause it to conk out. Had you acquired the new unit and the problem persisted that would be grounds to be a bit pissed.

You appear to have a false understanding of the knock sensor operation. If you have a knock sensor down [or the Hall sensor] the car will run OK but it will do so with 6 degrees of advance removed from the mapping across the board and that will lose a chunk of power/torque. If you have never had the thing running correctly you would probably not notice the loss but if the problem were corrected you would most likely notice it immediately. It is easy to simulate this effect- just unplug one of the two knock sensors in the engine bay. If you sense "no difference" then a sensor was down already. If you disconnect and sense a noticeable drop in performance then the sensor you suspect is "good". The knock sensors are there primarily to protect the motor if you inadvertently fill with a lower octane gasoline or for whatever reason are obliged to fill with some Witch **** due to unavailability of that required. A working system will immediately pull timing from any cylinder that is knocking and can pull up to 9 degrees in three "3 degree" increments but at quite some expense to output. Despite what some seem to think, the EZ is a very sophisticated system and reacts very quickly such that even at high rpm's if a knock is detected by the time the next firing event occurs it will have implemented 3 degrees of retard on the cylinder that knocked in the map cell the event occurred in. Pretty impressive for a system designed in the mid 80's.