Leon Speed

It might be obvious for most people here, but for those who didn't check their knock sensors yet, please do so.

I bought a diagnostic tester recently, which revealed a faulty knock sensor and a erratic knock count - especially on revs. Some reading and advice from others suggested cleaning the sensor connectors first. When I did that for the front sensor, the insulation of the wire fell apart in my hands. The sensor lead is clamped to the intake with a metal bracket. The insulation is also missing there.

So it appears I have been driving for more than a year with at least one faulty knock sensor, thus with 6 degrees retarded ignition On the bright side: I guess I found some more HP

So once again: check those sensors!

Peter F

Yepp, replace and then floor it
Mine was the same and I replaced both when alreday in there.
I'm sure you will feel the difference.

/Peter

Jim bailey - 928 International

Knock sensors , faulty hall signal units , stretched accelerator cables , unhappy flappy , bad cam timing , old Mass airflow sensor ; all things which keep an S-4 from running like an S-4. Standard answer to how do I make my S-4 faster ? .........First make sure it runs as well as it did when it was new !

SeanR

Yup, check 'em.

Both of mine were gone with I did the intake refresh. Most every car we come across has 1 or both gone.

Peter F

And to add to Jim's listing a new O2 sensor gave my car better throttle response as well.

/Peter

John Speake

I would also add "faulty WOT switch" to Jim's list, if "adjust trottle cable doesn't fix the WOT signal.

Jim bailey - 928 International

Peter and John good points as always ! There are so many things that can cause power loss that MANY 928s are not living up to their potential.....and bolting on a blower makes little sense if all of these and more are not addressed FIRST. If you are stopped and push the gas pedal all they way down 14 seconds later you should be going 100 MPH or more .

John Speake

...................and only about 1/4 mile down the road :-)

ekeeton

+1
When I first drove my 89 s4 it seemed pretty awesome, to me anyway. Then I had an intake refresh and replaced both knock sensors. The difference was stunning. WOT switch, new O2 sensor, new MAF, don't know if I could handle it.

oz928s4

Can you enlighten me in regard to the intake refresh....different manifold..???

soupcan

http://members.rennlist.com/pirtle/svc.html

oz928s4

Ahah thankyou

David L. Lutz

All the above items mentioned have been replaced with new recently, and would like to think all is functioning 100%. However I would like to verify that, but I don't have the need to do any tuning. (no sharktuner necessary)

Could someone advise me on the least expensive diagonstic tester that will do this on MY 87 ?

soupcan

+1 MY 87 Also.

the flyin' scotsman

Replacing all gaskets, the knock sensors and ensuring the TPS, ISV etc are all well the improvement is very nice................car revs very free and SOTP power is largely improved