Ignition retarded - Knock sensor?

[Peter Milnes]

When the clip is released the plug should lift up at one end and then be disengaged from a clip at the opposite end to the cable entry. This is similar to the ABS Control Unit and the ECU plug. Remember that the ECU AND ICU are interconnected. I think the knock sensor works via the ECU to alter the ICU. As I said before the sensor will have no effect whatsoever and cannot send a retard signal to the ECU/ICU either, if it is duff.

All the best, Peter

[pony1975]

Can anyone help me please. My 98 945 turbo had been having intermittent issues. It would randomly cut out, after a few times of turning the engine off and on again it would cough splutter then be OK. It would then be weeks /months before it would do it again. Then sometimes when I put my foot down hard(with the boost turned up) it would start to miss fire, then it would be fine for weeks at a time also. So finally in November it died. After some research online I changed the icu for 1 I had in my shed from a car that got written off n I gutted it. It started up fine. Tested it and ran fine till I put my foot down n it is still missing under load. So I take the mbc off, put it back to LPT, no change. Swop the maf, no change. Put a new crank sensor on cos the outer cable was splitting, no change, new fuel pressure reg, no change. Then on a test had a huge backfire n lambda light came on. Put a new lambda in n no change and lambda light came back on after I cleared it. So I borrowed a mate's genuine volvo fault reader. It read faulty knock sensor, fitted a new 1 still no change! More research, tested the wires 12 & 13 to the icu, they are fine, got 0.75v to the fcu on pin 28, but I'm only getting 0.05v at the knock sensor between 1 wire n the battery negative, 0v on other wire n 0v across both plug wires not the 1.5-5v I should. I've swopped the fcu and got no difference in voltage also. Is my replacement icu no good or can anybody recommend anything else to try?????

[Laird Scooby]

Originally Posted by anlo

I'm trying to figure out a way to check if the knock sensor is the source of my problems instead of just replacing it. Assuming a functional sensor - when disconnecting the wiring from the sensor, ignition timing should go to full retard because of no signal sensed, right?

If the timing doesn't change (with trottle microswitch disconnected or gas pedal depressed slightly), the knock sensor or its wiring should be suspected.

Any other ideas for isolating the retarded timing problem is welcome. I read about connecting a LED and a resistor between +12V and sensor output and checking for flashes while driving. I'm not sure of what that indicates though, does the LED flash when the sensor detects a knock?

Best regards

/Anlo

Unplug the knock sensor and drive it. The idle switch is NO, should be closed with throttle at idle. Check the ingtegrity of the vac pipe from inlet manifold/carb to the bulkhead and inside the cabin where it goes to the ignition EZK ECU. Make sure it is plugged in to the EUC as this will cause the timing to be retarded.

Also what fuel are you running on?

[Laird Scooby]

Originally Posted by pony1975

Can anyone help me please. My 98 945 turbo had been having intermittent issues. It would randomly cut out, after a few times of turning the engine off and on again it would cough splutter then be OK. It would then be weeks /months before it would do it again. Then sometimes when I put my foot down hard(with the boost turned up) it would start to miss fire, then it would be fine for weeks at a time also. So finally in November it died. After some research online I changed the icu for 1 I had in my shed from a car that got written off n I gutted it. It started up fine. Tested it and ran fine till I put my foot down n it is still missing under load. So I take the mbc off, put it back to LPT, no change. Swop the maf, no change. Put a new crank sensor on cos the outer cable was splitting, no change, new fuel pressure reg, no change. Then on a test had a huge backfire n lambda light came on. Put a new lambda in n no change and lambda light came back on after I cleared it. So I borrowed a mate's genuine volvo fault reader. It read faulty knock sensor, fitted a new 1 still no change! More research, tested the wires 12 & 13 to the icu, they are fine, got 0.75v to the fcu on pin 28, but I'm only getting 0.05v at the knock sensor between 1 wire n the battery negative, 0v on other wire n 0v across both plug wires not the 1.5-5v I should. I've swopped the fcu and got no difference in voltage also. Is my replacement icu no good or can anybody recommend anything else to try?????

First, the Lambda light as you call it is very little to do with the Lambda sensor, it's an engine management light. Have you checked the obvious stuff like the dizzy cap, particularly the cabon brush in the cente of it inside? These have a habit of breaking. Also check your HT leads and plug gaps which should be 0.65-0.7mm.

Also reset all DTCs and then try again after checking/renewing the dizzy cap and rotor while you're at it. Then if there are any faults, read the DTCs and see what you've got.