Knock sensors??

[Shaper79]

Has any had to replace knock sensor?s to regain max WOT Rpms. Iv went threw my intire fuel system and firing system. And all checks out fine. Only has 170H on 2000 5.7 Volvo 94-99 motor. No smoke no oil burn. But can only hit 4200 rpms WOT 3 people in boat 19 pitch prop. I?m thinking maybe the knock sensor is possible bad or both of them if there is 2 and retarding the timing. I run 89 octane. Thx.

 

[Scott Danforth]

before you go replacing anything, have someone hookup Rinda and check. you can then see if the knock sensors are active. however most likely, it isnt the knock sensor as that little piezo sensor is nearly bullet proof.

Throttle Body or MPI?

what is your fuel pressure?

have you checked your anti-siphon valve? content of fuel filter?

 

[Shaper79]

Throttle body. I seen that Rinda. Is it like 400$ for the hand held scan tool? Yes fuel pressure was all in spec. Low pressure at 7 psi. And high at 30psi steady. I think the motor is rated at 270 HP. Maybe a little less now that it has 172.0 hours. Is that enough to turn a 19 pitch 216ssi. At 4600 rpm ? I know my tac is right cause I wired in a auxiliary tac to cross reference

 

[alldodge]

The easiest way is a scanner to see if the knock sensor is retarding timing. Only other way is attach a timing light and when running check the amount of advance.

 

[Shaper79]

Yea. I guess I?ll do the timing light. To see if it is advancing.

 

[muc]

you don't post a serial number so i can't be sure. but my guess is the ECM won't know if you disconnect the knock sensors for a test run. Make sure to ground them.
more common to see misrouted spark plug wires cause a false knock event than a bad sensor.
If my memory is correct that boat should have came with a 21p prop new. If so, it sounds like your down 12% = 1 cylinder not working. Might want to do a cylinder balance test. Or if you can't do that check the compression. This is also assuming your near sea level and not at high altitude.

 

[Shaper79]

Good to know. I?ll prolly have do that compression test. If it?s advancing correctly

 

[Shaper79]

Only thing is. Is that the motor runs smooth and all plugs are firing. I couldn?t imagine a cylind would just have little to no compression.

 

[alldodge]

Only thing is. Is that the motor runs smooth and all plugs are firing. I couldn?t imagine a cylind would just have little to no compression.

Muc brings up a good point, but it might not be one cylinder, it might be a tad off two or three

 

[QBhoy]

My knock sensor alarm came up a few times as a side effect of a faulty distibitor cap.
Thing with these engines (perhaps less so with the throttle body FI) is that sometimes if one electrical fault or gremlin is present, it has a knock on effect on a few things.
As mentioned, best get it plugged in.

 

[Shaper79]

Yea I?m going to buy the Rinda hand held scanner , in February when I get threw all this holiday spending. I thing the unit was 400$. Cause this guessing game is getting old.