persistent knock sensor code-kind of fixed?

[RickHaleParker]

hows this for weird..i placed the rear sensor back to its normal position 3 with copper washers and i got the "knock code" moved it back to position 2 and no "knock code"??

Postition #3 is abnormal for either sensor.

The front knock sensor is suppose to be on cylinder #2. Mounted with the wires at 3:00.
The rear knock sensor is suppose to be on cylinder #4. Mounted with the wires at 6:00.

Front Knock sensor listens to 1,2,3. Rear listens to 3,4,5.

1,2,3,4,5

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Install the new sensors. Tighten by hand.
1. Route the cables on the outside of the starter motor bracket.
2. Align the sensors. The cable from the sensor for cylinder 2 = 3 o'clock and from the sensor for cylinder 4 = 6 o'clock.
3. Tighten the knock sensors (KS) to 20 Nm.
4. Connect the knock sensor (KS) connectors. Check that the wiring is in the correct position..
5. Secure with a tie strap at the starter motor bracket.

Knock_Sensors.png (47.69 KiB) Viewed 1141 times

volvo knock sensor locations a.jpg (205.88 KiB) Viewed 1138 times

[SuperHerman]

I would add - clean surface of block so it is smooth. Add a very thin film of dielectric grease. It should prevent oxidation of the AL and provide a nice contact surface.

Based on RickHaleParker's information the sensors are working correctly - meaning you have a problem and your moving and spacing is masking it.

[darrylrobert]

seeing some forums people talking about carbon build gradually started pinging on high octane fuel, so i havent pulled the spark plugs yet but i think/hope that is the problem.

Ive ordered 2 bottles and a spray bottle of seafoam, some of the 24hr seafoam before/after videos dont look that impressive, but one guy left the seafoam in for 10days and got impressive results. I might try 2 or three days, do you think that is risky? Ive also ordered Redline fuel system cleaner that has very good reviews.

[abscate]

Fine to leave in for a few days , but remember...

Engine displacement is 2.5 liters/5 roughly 500 ml per cylinder

Compression ration about 10:1

Volume compressed is about 50 ml

Pouring in 100 ml of fluid more than fills the cylinder when compressed. , so be careful turning it over until you know the liquid is out.

[RickHaleParker]

Fine to leave in for a few days , but remember...

Engine displacement is 2.5 liters/5 roughly 500 ml per cylinder

Compression ration about 10:1

Volume compressed is about 50 ml

Pouring in 100 ml of fluid more than fills the cylinder when compressed. , so be careful turning it over until you know the liquid is out.

Displacement = 2435 cc.
Compression ratio is 9:1 = 9/1 = 9.
2435 cc displacement / 5 cylinders = 485 cc / cylinder.
Combustion chamber volume = 485 cc / (9-1) = 60.625 cc. 1cc = 1ml. 60.625 cc. = 60.625 ml.
CR = (Vd + Vc) / Vc
Check" (8 * 60.625 cc + 60.625 cc) / 60.625 cc = 9 = 9/1 = 9:1.

A liquid is only slightly compressible. That why you need to push out the liquid before installing the plugs.

[SuperHerman]

GM makes a great solvent for carbon build up. Use it in the same manner as the SeaFoam application being discussed. I have used it with great success.

Like RickHaleParker and abscate mention - hydrolock is a concern. Put a rag on the spark plug well and spin the engine over with the starter. The fluid will be forced up into the rag.

Not sure on the Volvo if you have to pull the fuse for the fuel pump and possibly the ignition coils. Some one will chime in.

[erikv11]

Agreed, what abscate said:
- fine to leave it in for few to several days
- cylinder volume is about 50 ml on full compression stroke; bottom line make sure the liquid is mostly out of there before plugs go in

[WhizzMan]

My upper engine mount rubber (square type) moves inside the bracket or upper strut is knocking, i can hear it sometimes while coasting however i find it hard to believe this is triggering the knock sensor?

It was my first suggestion to check after only reading your topic title. This is so often the cause of knock retard that it should be on top of the checklist. Fix all your engine mounts and put the knock sensors and timing to factory spec before you start fiddling around. Stage 0 tuning needs to be okay even for none tuned cars. On my old 850 T5 I couldn't get it to stop retarding (and thus do any tuning) until I had all of my mounts sorted out. I probably gained over 20 HP (that it was down from factory) just by sorting this out.

Knock sensor circuitry (and in some cases, programming of the ECU) is tuned (more or less, depending on brand/type car) to your specific engine and knock sensor location. Basically, the ECU listens for specific frequencies at specific crank angles ranges to determine if there is engine knock and to correlate that to a specific cylinder. These frequencies are the natural resonance frequency of your entire engine block. You can test knock sensors by hitting the side of your engine with a spanner and looking at the analog signal, or use whatever diagnostic features your ECU might have. If you can hear your engine banging inside the cab because of play on your engine mounts, you can be certain that the knock sensor is picking it up as well. The knock sensor can't tell if the banging on the engine block comes from an engine mount or from an explosion on the inside of a cylinder.

[SuperHerman]

Based on the facts I think WhizzMan's explanation makes great sense - pointing at the various mounts.