garychios

Looking to replace the knock sensors. The car does not make the same power when hot. It flies when its cold, not that its slow when it warms up, but I am sure the knock sensors are pulling some timing when they warm up. And because the PO did no maintenance, I am sure they need replacement.

I am using PET tofind the parts to no avail. Any recommendation on where to look for these sensors. I am sure the 911 has 2 of them.


Thanks

max911

PET

year-98
MG 9
SG 01

Illustration 901-03

diagram part # 7

Bill Verburg

You can see the knock sensors nad wiring bolted to the cylinder bases here

Steve Weiner-Rennsport Systems

Gary:

I'm not the last word on this subject but I've NEVER seen bad knock sensors on these engines and that goes back to 1989.

Your observations are valid and I'd address the root cause as you are simply feeling the ECU do its job to prevent the engine from being damaged by detonation.

I would plug in the PST-2 and watch knock sensor activity in real time to see what is going on. An experienced technician will know how to interpret the results. If your car is chipped, I would ask you about that as many chip tuners get greedy with the timing maps and that certainly triggers what you are feeling. (I see a lot of that sort of thing)

After all that, I would:

1) Check distributor drive belt

2) Make sure you are using 93 octane or better fuel. If your car is aggressively chipped, you might need 100 octane fuel.

3) Make sure that the oxygen sensors are functioning correctly.

4) Check cam timing.

Hope this helps,

garychios

Steve,
The belt is fine on the distributor. Just tested it.
I run 93 Octane all the times

I might need someone to check cam timing. I dont trust any local Porsche mechanics in NY.

Also, I thought from my experience, that the 02's dont matter at WOT. I mean, I run Fuel Injected race cars, and we dont run 02's becasue we are only concerned with WOT and they are passive at that point. PLease elaborate if you think the 02's function differantly in a Porsche. Are they a wide band typoe of 02 and the ECU regulates at WOT? This is a huge differance than any other Fuel Injected car.

Also a couple of more questions.

How is timing adjusted on these cars when driving? I know the ECU does it, but how is that translated the distributor?

How can I check cam timing myself. I am an experienced straight 4 cyl builder, but nothing like a boxter motor.

Are the knock sensors wax filled? If they are, then surely changing them will yield more power.

I have fixed sooo many cars power problems just by replacing old knock sensors

Thanks