gonzilla

Maybe Tony C can back me up on this, since he's the one who told me... If you are using Chevron fuel, you should NOT be adding any additional techron or techroline. Can't remember the exact reason, but I remember it not being a good thing.

dbf73

have you tried another tank of fuel - either Chevron or another brand? eliminate the bad fuel possibility first

Bill 993

Chevron states on their website that adding the bottle provides a concentration 10X what is provided by just the Chevron gasoline. I typically added the bottle in the tank before an oil change. I agree, benefit could be questionable, but figured it couldn't hurt.

So I think my plan will be (in order):
1. Try new gas brand (on next tank)
2. Try to determine if my 993 has had the ECU programmed
3. Look into using Bosch tools to determine pinging events and/or determine if plug wire / timing related

Likely will take me a week or so to work thru this list.

Lorenfb

"determine if plug wire"

Easy to do by just disconnecting the power lead to each coil one at a time,
i.e. This removes one of the two ignition systems completely which then
will isolate an ignition plug wiring problem.

VNTGSPD

This is interesting and got me thinking about my car.

My car regularly pings for a second or two when aggressively opening the throttle from mid-RPM ranges. It goes away so it sounds like the computer is doing it's job and the best fuel I can get is 91 octane. I always assumed this was normal due to the fuel available here.

Is this normal or are there components such as plug wires that will reduce/eliminate this? The car is a '95 with stock chip, 106K miles and does have new cap rotors oil etc etc.

Thanks.

TCallas

First off, I would be careful NOT to add additional Techron IF you are using Chevron fuel because I have found that it has a tendency to wash the cylinders somewhat. I am sticking to my "Software Issue" educated guess. By the way, I am with Geolab on the bet. I am sure they did it but make sure they check the distributor drive belt really well. It's been a long time since I have seen him, hello to Walter for me.

geolab

+1, cheapest method is a can of octane booster enough for 72 litres.

Technically, a cheaper method is to add water to the gas to raise octane level , but measurement has to be precise etc...

There are two distinct things here that may be occuring with same effect and draws to confusion,
1-pre-ignition and 2-pinging/knocking.

To generalize, pinging is more mechanical, timing, heat, pressure, etc.
pre-ignition is more octane, gas, carbon, etc.

try octane booster, if all goes, its the gas

TCallas

Geolab, sounds like a good plan to me.

billpor930

If you're sure the distributor drive belt is intact, another thing could be that improper spark plugs were installed. If the heat range is too hot, pinging could be the result.

Steve Weiner-Rennsport Systems

A few thoughts,.....

1) 91 octane is quite frankly, marginal for these cars. Porsche knew this and printed their octane requirements in the owner's manual and thats based on obtaining maximum performance.

2) That said, these cars should NOT knock on 91 unless there are other issues at work.

3) Based on what I've observed, engines with 106K on them have a lot of carbon buildup on the piston crowns and chamber surfaces which both raise the mechanical CR as well as provide a source of self-ignition (hot spot) that can trigger detonation and/or pre-ignition.

Davies

Just to let you know, I tried all of these when experiencing pinging (detonation) at 3000 RPM and up.
(hope this helps.)

-octane booster = Still pinged
-different gas = Still pinged
-new plugs = Still pinged
-new caps/rotors = Still pinged
-checked dual dist belt = Still pinged
-swapped out knock sensor = Still pinged
-swapped out ecu = Still pinged
-new O2 sensors = Still pinged
-new plug wires (after seeing spark arcing from one wire to another at 3000 + RPM) = Bingo!

Lorenfb

"new plug wires (after seeing spark arcing from one wire to another at 3000 + RPM)"

As mentioned before, it only takes 1-2 minutes to disconnect an igntion coil
to isolate bad plug wires.