Bill 993

I just had my normal service (oil, trans fluid, air filter, new brake fluid) completed at my local independent shop. They did a test drive and noted that I have engine pinging around 3,000 rpm. I have noticed the pinging myself, so wasn't surprise. They suggested I use a different fuel. I find this interesting since I always use Chevron Supreme (from 2-3 different stations).

Anyone else have bad luck with Chevron vs others (Shell or ?). I had always heard / assume that Chevron was a top quality grade.

Note, I have only ~44k miles on my 1996 993.

Thanks.

MarkD

OK, I'll get the ball rolling. Based on what you described, it's not the fuel.

Aftermarket chip?
Does it do it hot and cold?
Did they eliminate other possible problems with ignition?

TCallas

Bill,

I agree with what questions and comments that MarkD has. I would suspect that it is not the Chevron Supreme (92 Octane) fuel that you are running. Has someone driven your car to redline while under full throttle to make sure that all the carbon is blown out? Other than MarkD's questions, I would also look closely at the Distributor's internal drive belt and internal timing. How old are your spark plugs? Make sure that your car is not overheating. The maximum recommended oil temperature is at the white 10:00 O'clock mark. Normally the engine will run between the 8-9:00 O'clock white marks. rfe you sure that what you all are hearing is engine pinging?

Bill 993

Hi Tony, FYI - you did my PPI on this 993 back in Aug 2002!

No aftermarket chip.
Normal running temp. Here in Seattle, I rarely see oil temp. above normal. Usually at low end of range.
They pulled 3 plugs and reported all look normal (were replaced at 30k, so 14k old).
They check the dist. (rotors) and also spark plug wires - reported normal
Did not check timing.
I make it a habit to give the car full throttle (after warm-up) often (I was getting the Porsche serviced for a track event on 20-June)

Gerber Motorsports does my work in Seattle. I believe they are correct in hearing pinging.

Stealth 993

Gerber is a great shop, I would have them test the MAF & the engine temp sensor. If these read wrong it can cause the car to ping. So can a vacuum leak.

I run the same fuel, & might even get it form the same places, so far no issues.

If it is deposit related, run a can of BG44, Redline SL1, or Amsoil PI.

Bill 993

They did check codes using a Bosch KTS300 and found no faults. They also added a fuel cleaning additive (don't know the brand). I've been adding a 16oz bottle of Techtron every 3,000 miles (for last 4 years).

I should mention the pinging isn't severe, would take several full throttle runs to notice (if at all). I wasn't sure I heard it, until Gerber mentioned they heard pinging after the test drive today.

Davies

I'll bet a dollar you have an arcing plug wire.

geolab

I bet one dollar it is not an arcing plug wire

Lorenfb

"Note, I have only ~44k miles on my 1996 993."
"No aftermarket chip."

Unless it's a late '95, the '96 had a masked memory chip,
i.e. not removeable nor a EEPROM (flashable).
So, are you sure that the DME ECM has never been removed/replaced?

A simple check would be to use a Porsche PST2 tester and monitor
the knock count as the pinging occurs. Also, the tester can monitor
the ignition timing. One can also disconnect one of the two ignition units
and try and isolate the problem, i.e. an ignition system, or increased pinging
(single plug mode). Additionally, check the knock sensor system with the
tester, i.e. if the that's non-functional the engine will probably ping under
some load conditions.

Davies

You're on. Except if it is an arcing plug wire, you have to send me one Euro...

Davies

My reasoning for such high-rolling confidence and swagger is, a long time ago I tore my hair out with the same symptoms. After an exhaustive (and frustrating) process of elimination, it turned out to be just a plug wire arcing, even though the wires "looked fine." The way the wires look vis-a-vis the way they function are two different creatures in my experience.

geolab

You're on

Bill 993

Thanks Loren, very good ideas. I'm talk with the shop about using the tester to capture the pinging. Since I purchased the 993 used, can't be 100% confident that the ECM haven't been upgraded. The original owner did provide all his receipts and full disclosure so think he would had mentioned.

AOW162435

When buying a used car, the owner may indeed provide Full Disclosure. Full Disclosure of only those items that he or she feels like disclosing.
On other items, he or she may provide Full Closure - of his or her mouth with respect to items that may be detrimental to the sale of the car.....

A sad reality.

I went through a pinging issue which completely disappeared once I replaced the stock chip.


Andreas

robroy72

Not sure if this would be the source of the issue ... but why are you adding Techron to Chevron fuel? They started adding Techron to all grades of fuel a few months back.