WRXsteve

My95 WRX was showing 8 deg of retard during a test run with a select monitor. Although no fault coeds were present could this be a faulty knock sensor...The power drop is huge! I have also replaced the following which has made no difference:
boost solenoid
new hks plugs
coil packs
lambda probe

The above has cost me a lot of money in garage time....Any idea's????

Steve.

DrEvil

SUL and Octane Booster will do the trick

WRXsteve

I am already using sul (shell) and Millers.

Steve.

Col Stone

HI
I had 8 degrees on my 93 WRX last year.Was running sul+millers. Changed the boost soleniod, manifold pressure senser ect,ect. Each time leaving 2 weeks between to see the difference(none) It turns out the ECU has a knock panel which is mounted vertically and gets damaged by excessive vibration i.e crap roads and hard (WRX) suspension. Only cure a new ECU!was told to try a link but was to expensive. The fault was confirmed on Power Engineerings rolling road. I got a second hand ECU from Scooby Sport fitted it in 10 minutes and it's been a dream to drive ever since!
Sorry it's bad news but good luck
Cheers COL

WRXsteve

I hope it isn't the ecu! I am trying a knock sensor first, if not is there anyone who can test the ecu out of the car?

Steve.

russell hayward

Surely if it was the knock sensor, you would get the fault code showing on the Select Monitor ?

WRXsteve

I thought that also. However I am told that it may be faulty even though the select monitor doesn't pick up the code.

Col Stone

Hi Steve
Sorry to be full of doom and gloom! I changed the knock sensor as well but it made no difference. The ECU is detecting knock even though the engine is OK, we listened to the engine on the rolling road with a stethascope (nice spelling)
Sorry Col

Jan Shim

"ECU has a knock panel which is mounted vertically and gets damaged by excessive vibration"

Col, I would love to see a photo of this Knock panel you mention. Perhaps i am missing something here but from my '95-'99 ECU experience (to fit PossumLink ECU, KnockLink and LambdaLink monitors), I have NEVER seen anything resembling a "knock panel" .. perhaps you're referring to the kick panel that protects the ECU from being kicked by passengers?

A knock sensor (microphone) is fitted to the engine block in close proximity to one of the cylinders, in stock form, near Cylinder #4. No way would any disturbence or shock to the ECU unit will trigger ignition retard. The ECU board has nothing but chips, diodes soldered to a printed circuit board.

Steve, I can't see how your WRX could have retarded ignition timing if the knock sensor is defective unless a defect means it has become MORE sensitive instead of completely malfunctioning as in, absolutely no feedback to the ECU.

Col Stone

Sorry I haven't a clue on link ECU's ect.
Open up the standard ECU and as you say it's all flat except one vertical pcb. This is the pcb controling knock. Hence why it is damaged by vibration.
If you want someone to argue with speak to Mervyn at Power Engineering or speak to Scooby sport
Cheers COL.

WRXsteve

I just tried a ECU from another WRX. Problem still there!
I have also swapped the knock sensor and the pressure switch, which had made no difference. Any other idea's.....

I have noticed the problem gets worse the hotter the car gets.

Steve.

WREXY

I'm no expert Steve and could be talking out of my '****'. Since you tried another sensor and the same thing happened, it seems your knocksensor is picking up some type of noise, whether it's in the motor or something external near the sensor or maybe a vibration. Looks like a job for the experts now.

WREXY.

Jan Shim

What surprises me is my workshop manual says the standard ECU retards up to 5º on detection of knocks but you are getting up to 8º. Got me thinking if there's a limit to how far the ECU would retard.

By any chance does your WRX have an Inlet Air Temp (but i guess you're referring to engine getting hot and not high ambient temps). Only STi's from '97 on have IATs as standard so it cant be the ECU retarding timing from too high an ambient.

Check that there is nothing loose such as BOV hitting the engine block. We had a problem with an STi 4 the BOV wasnt secured and it was hitting the intercooler and the knock sensor picked that up and retarded timing. Also is the engine generally very noisy?

R19KET

Steve,

The first thing you should do, is get a set of DET' CANS on there. This will identify if the det' is "real", or spurious.

It's possible that your car has developed a particular resonance (maybe rev related) that sets the knock sensor off.

This is a fairly common problem on some cars. If you can establish the car is running "clean" (with det' cans) and the fuelling is safe (RR, select monitor, or Lambda Link) try moving the knock sensor to another less sensitive place.

Mark.

WRXsteve

I do have a HKS exhaust (very loud), could it be causing the problem as it only happens at 4500rpm.

Steve.

Jan Shim

Now this reminds me. I fitted a KnockLink to an STi 2 Type RA 555 and this car suffered from a phenomenon called 'shift knock'. The KnockLink would light up like a x'mas tree in every gear on WOT shifts. Really weird. Perhaps this is what's happening with your WRX and it became evident only with the KL monitor. I'm sure the constant "knocking" isnt doing the sensor a lot of good. Hope this makes sense.

WRXsteve

What is "shift knock" and how can it be cured?

Jan Shim

" I do have a HKS exhaust (very loud), could it be causing the problem as it only happens at 4500rpm. "

Is that what the SELECT Monitor showed? I would first of all remove the HKS exhaust, fit a quieter or stock unit to eliminate this as a possibility or fit a silencer bung if that helps tone down the resonance.