cobalt

Only 25 out of 400+ GTS owners here.

worf928

Interesting stats folks. Thanks for participating.

928ntslow

Looks like this thread died a quick death.

I said I would put a list together a list of things to compare, but I would like to find out first if anyone simply changed out their spark plugs to factory spec'ed (correct heat range). No fancy cra plugs, just a straight single copper electrode like a Bosch.

Just as an example. I have a Ford F150 that I had purchased new in 1992. It now has 295K miles. I have changed the oil every 3K-4K and only used Mobile 1 since the day I had bought it. I had always used distiled water and a 60/40 mix. However, at some point I starting using "hotter" spark plugs. I believed that a so called "better" plug was going to give me more power and who the hell knows what else.

Anyway, whenever I would put the truck under heavy load or up a hill, I could hear pinging. I tried at one point to "dial" out the ping in the timing adjustment. It seemed to help some, but I could have been imagining it. I chaulked it up to having over a quarter million miles on the engine and she was getting tired.

So just for the hell of it (and thinking about this thread) while shopping for items for a complete tune up and service for the truck this past weekend, I made the purchase of the factory speced plugs. They weren't Motorcraft, but Autolite. I think they make the Motorcraft plugs, but the same spec'ed plugs.

I pulled the old plugs which looked great, nice tanning and the gap was near perfect. They were Champion Truck plugs. They were supposed to be "better" for a truck engine...you know, bigger ***** kinda thing.

Did the tune up, installed the factory spec'ed spark plugs and ran the crap out of the truck.

NO MORE PINGING! I even turned on the AC full blast while driving up a long grade at 70mph...NO MORE PINGING!

So maybe my theory about too much heat is correct, as it seems like a hell of a coincidence that my truck that had been pinging for wayyyyyyy too long, NO LONGER PINGS!

Does anyone that has a GTS with this pinging issue want to change their plugs and see what the results are? This could be THAT simple.

Thanks

worf928

I'll revive it in a week or so. Right now I don't have time to do this subject justice.

Yes. I do. First I'm going to pull a plug and check the code. Then I'm going to

a) drive the GTS to verify pinging with respect to throttle switch polarity
b) upgrade my Spanner software to see if it will then work on my GTS
c) check knock sensor codes
d) change to proper cold plugs if those that are installed are incorrect
e) use a top-end cleaner
f) change out the MAS for a new one I have in my '89

928ntslow

I think it may be of some value FWIW, that I had added a quart of RISLONE with the new oil change. However, this would NOT make instant changes in compression ratio reduction eliminating ping. I will testify that RISLONE is just plain awesome for a high mileage engines. It will most certainly clean the inners without damages and restore some lost performance. RISLONE has been around for many many years. The single most thing I did to change the issue was the plugs. I hadn't touched the timing.

Good luck Dave and I hope you come up with some valuable info. I would love to see this mystery, uhmmm, de-mystified!

Drmark

Dave,
Found something that may be interest to you - my Hall sender resistance was too high. Replaced it and guess what? The knock sensor and EZK faults dissapeared too. John Speake had verified that the EZK was working fine and I replaced the knock sensors last year so didn't trust the Hammer - seems a Hall sender fault throws up the others. Interesting given that a number of cars have had "EZK failure" and more than one set of knock sensors. In future may be worth check the Hall sender first.
Anyway no pings now - but I am running a GT EPROM so will try my original GTS one in again.
Not that I really understand any of this, but my experience may be of some help.
Cheers
Mark
__________________

John Speake

Hi Mark
I am puzzled by the comment "hallsensor resitance too high." It is a semicinductor device, just gives 0 or +5v depending on where the cam disc gap is. You can't really do a resistance check on it...

It could give a low output, I suppose.

Anyway, glad that a possible reason for you knocking has been found !

Let us know what happens when you chenage back to the GTS chip. We are all on a learning curve with this stuff...

Regards

Drmark

John,
Quad erat demonstrandum! As I said "Not that I really understand any of this".
It was Paul A who sussed it doing the checks we discussed - I must have misunderstood him. Either way it wasn't working as it should, connectors were fine and the new one sorted the problem out. Think I'll stick to humans - no semi-conductors (that I know of!)
Cheers
Mark

John Speake

OK Mark,
I am intrigued as to what the fault was. A hall sensor is basically a semiconductor switching device either on or off.

Let us know how things progress...

928ntslow

I am not sure if this is a contributor to your issue of the Hall sensor, but the connectors DO tend to deteriorate from heat exposure. I had experienced this with my GTS when doing a full service at the time I had purchased the car. The connector had just crumbled to bits. I had no choice but to remove it. At the point I had it out of the car, the only thing left of the connector was the 3 exposed pins and half of the lower most part of the plastic connector. Hall sensors run about $80USD and I was having NONE of that! I cleaned and refitted the pins then encased in an epoxy resin. I filed and shaped the plug back to its original shape and reinstalled. Worked like a charm.

Threw the Hammer to the car sometime later and cleared the old Hall sensor fault...which hindered the performance of the engine all that time I had found. The fault never returned so I guess I did my job well enough. Unfortunately, just fixing or replacing the Hall sensor without clearing the code does no good with my experience.

I am not sure, but is the Hall sensor disc "keyed" on the cam end? I forget. I know that the Hall Sensor and the Sensor at the Bell housing must work in unison to properly read time. I believe this is the reason the 928 doesn't fire up as soon as the ignition key is turned. There must be at least one revolution of the components to read timing positions. So, if the Hall sensor disc is not "keyed", this could be an issue that contributes to pinging. Though I seriously doubt it is not "keyed"....just rambling here

John Speake

Hi Keith
A battry reset would also have cleared the Hall fault code...

The Hall sensor is timed fairly accurately relative to the camshaft. I am not sure that the Hall is the reason for the delay in the engine fiiring, that is more likely the EZK sorting out where it is relative to the gap in the teeth of the timing ring (flywheel).

The Hall is used to help the EZK work out which cylinder has detonation. The EZK then retards the igntion on a per cylinder basis. Clever stuff...

If the flywheel speed sensor fails, then the EZK uses the Hall signal to give a "get you home" spark timing, although this is not as accurate as the flywheel sensor.

928ntslow

I would expect you are correct John. I knew that these sensors had a hand in the whole chain of events somehow.

As for the Hall sensor fault code, it seems that when Dan Warner of Exotic Motorwerks threw the Hammer on my car, it picked up the hall sensor code along with many disconnect codes. I had disconnected the battery several times since fixing the sensor. I know I am not imagining this as Dan can back me up. He showed me the codes. HOWEVER, there MAY be some weird possibility that the Hall sensor got tripped again, but I cannot for the life of me figure out how it would have. Never the less, Dan cleared all the codes. The car came to life (I had posted about it last year some time). We checked the codes the next day, after I had put close to 100 miles on it and no codes came back. Still has a clean bill of health. Go figure. I had heard of another instance where the Hall sensor fault was not cleared by a battery disconnect. This was at last years Sharktoberfest as Dan had the Hammer to check codes for folks.

I think it may be safe to say that our cars are not all created equal...hence the ping

I am going to wait to see what Dave comes up with before I put together a list of things to compare from car to car. I suspect you would have some fine suggestions as well.

Thanks John!

John Speake

Hi Keith,
That's interesting feedback. I can't explain why that Hall fault was so reluctant to clear.

On my EZK test jig, if I am testing an EZK ECU and I switch off the Hall signal, then the igntion retards by the expected 6 degress at high loads/rpm. If I then switch on the Hall signal, it still stays retarded.

If I switch off the igntion, and on again, with the Hall signal restored, then normal timing is resumed.

I will remember your experience.....we are all on a learning curve about the mysteries of the 928's electronics !

Regards

Lorenfb

"If the flywheel speed sensor fails, then the EZK uses the Hall signal to give a "get you home" spark timing, although this is not as accurate as the flywheel sensor."

- John Speake -

Actually. once the flywheel sensor fails, the engine will die as there's no information
from the Hall sensor to keep the engine running other than a TDC for a certain cylinder,
or a relative engine timing position versus the cams.

Furthermore, a Hall sensor is really not needed to determine which cylinder needs
to be retarded because of pinging, but Porsche decided to use it for this purpose
on the 928. A Hall sensor (cam position) is really only needed for sequential
injection. Even for direct ignition, the ECM can determine the proper timing
relative to a TDC crank sensor.

"I had heard of another instance where the Hall sensor fault was not cleared by a battery disconnect."

There's NO non-volatile memory device in either the LH or the EZK ECUs.
Thus, once the battery voltage is removed, both ECUs lose their faults.

John Speake

>>>>>>>>>>>>

My typo - I meant to say I had NOT heard.....

..........but you knew that anyway...and there are EPROMS in both ECUs - non volatile.. :-).