Lorenfb

I should have been more explicit in my first post and that is;
make sure that your DME unit has not been modified, e.g. a performance
chip which is the most common source of pinging. Also, check
that the distributor belt is not broken and is aligned correctly.

The only time I hear about pinging on a 964 from my customers'
customer's car is when the DME unit has a chip or the car has some
real bad fuel.

Randall G.

>I should have been more explicit in my first post and that is;
make sure that your DME unit has not been modified, e.g. a performance
chip which is the most common source of pinging.

Yup, I agree. When I first joined Rennlist, I read about notorious "East Coast" chips that caused so much pinging that they blew up a turbo engine (or engines).

axl911

Have you checked the condition of the plug? Are they dark, rich mixture. Or white, lean mixture?

----
anthony

PC2

Doug,

Give the octane boosters or racing fuels a try. I did, and it proved to me that the substandard CA gas caused the pinging.

Arjan B.

Doug,

I had a Knock sensor faillure a while back. The ignition will go later about 6 degrees and your engine does not run in idle well then. After every start, the engine felt dead after using the clutch.
You clould disconnect all visable connectors and spray them with electric cleaner, then dry them with compressed air and spray them with eletric protection oil and put them back on. Then make a DME reset by disconnecting the battery and put the power back on after 10 minutes. Start the car and let it run in idle for at least 20 minutes.

Then try again. Let us know the improvements please!

Randall G.

Pete,

Curious. Are you running the factory chip?

Thanks...

PC2

Randall,

Yes, It's a factory chip. Funny thing is even my BMW Z4 pings during hot days.

Lorenfb

With all the mods on the PC2 car, I'm surprised to hear "no chip".

You've opened the box and have checked the EPROM for the
stock Porsche/Bosch part number? The label hasn't been removed
to erase & reprogram the EPROM? These days, you never know
what you'll find in DME units.

Randall G.

Thanks Pete, very interesting. Especially the Z4 pinging. That's both sad & amazing.

The wife's '96 Miata used to ping when running the recommended 87 octane, right after purchasing used in '99. Ran higher octane for awhile to get rid of the pinging. I'm back to running the cheap stuff, doesn't ping anymore. Go figure.

Obviously, the auto industry/enthusiasts lost the argument when California went to 91 octane gas. Does anyone remember when this happened?

PC2

Loren,

When I bought the car it was as original as the day it rolled off of the assembly line. PPI and leak down tests confirmed the car was immaculate and unaltered (including DME & EPROM). Every mod I've done so far are reversible and probably will when I do decide to sell. Besides, I've read enough here to know not to mess around with the DME.

scotsman60

First of all, thanks tpo everyone who has offered suggestions....


Loren - the DME chip is standard. One of your posts indicates that the DME can adjust timing on a per cylinder basis - is this true? I always thought that the timing was adjusted equally for all cylinders. If it gets adjusted differently for each cylinder then I'd only see the timing being retarted for the cylinder that's knocking right?

I plan to up the octane by mixing five gallons of 100 octane with my next fill up - probably tonight. Of course the temperatures this morning are down to 60 degrees here and I have no pinging whatsoever so this test may not be conclusive...... I'll probably also try using an octane booster and see what works best.

I can't let go of the thought that I also have a problem with my knock sensors - no engine light despite audible knocking (this indicates that the timing adjustment range has been exceeded and I should geta light right?)so I plan on investigating/testing/replacing - but after I've tried increasing the octane rating......

I'll report back with my findings.





Doug

Lorenfb

Because of the Hall sensor, the 964 will run in the sequential injection mode
and be able to adjust the timing for each cylinder. The 964 will run without
this sensor (not a good idea) and "fall back" to bank type injection and
won't be able to control each cylinder's timing.

You'll probably need the Porsche tester (the Hammer or the ST2) to properly
check the knock sensors. I assume that you did verify that the stock DME
chip number had the first 2 digits of "12".

axl911

Doesn't octane booster can cause problem to the O2 sensors?

BTW, does California still have the oxygenated gas? When they had it here in Dallas, my car would ping no matter what.

---
anthony

Randall G.

Hey Doug,

I don't think you should necessarily expect to see a CEL with the pinging. I've read of many people with pinging, and don't recall them necessarily getting the CEL. Pete, do you get a CEL with the pinging? Anthony, did you get a CEL with your pinging?

On the other hand, poor 993 owners with OBD-II get the CEL for all sorts of somewhat abstract and difficult to diagnose reasons. Misfires on an engine that seems to be running perfectly, secondary air injection, etc.

Here are some threads from the 993 board. Unfortunately, it appears that some of the most informative threads are no longer available on a search. But, I think you'll still find these somewhat helpful. Especially the first one, where the owner was also getting the CEL (a pretty bad case, apparently).

https://rennlist.com/forums/showthre...ighlight=knock

And, here's his fix = arcing wires:

https://rennlist.com/forums/showthre...hreadid=118669

And more:

https://rennlist.com/forums/showthre...highlight=ping

https://rennlist.com/forums/showthre...highlight=ping

https://rennlist.com/forums/showthre...ighlight=knock

PC2

Nope, never had the CEL come on or had a fault code generated.

My pinging are most noticable during uphills, low RPM, and open throttle. I suspect during high RPMs the pings are drown out by the sounds of the exhaust & intake.