knock sensor

[Racenut]

Where is it. And what does it do? I got a code 25. Knock not sensed during dynamic response test. Can it b tested? Do I need it?
And if its bad. Can it make my 2.9 run bad?

 

[adsm08]

The knock sensor is a piezo electric crystal that produces voltage when it vibrates at certain frequencies. The computer uses it to determine if the fuel mix is igniting too early.

The knock sensor was a big problem on the early 2.9L engines because it would interpret normal valve chatter as engine knock. It can cause running issues, particularly low power.

It you suspect a problem with the knock sensor it would be better to get an 88-92 computer rather than replace the sensor itself since the 88 model year deleted the knock sensor.

 

[alwaysFlOoReD]

I didn't know the early 2.9 has/had a knock sensor. Where is it located? I parked my 86 2.9 ranger because of drive-ability issues over 4 years ago. I've learned a bit on TRS since then and with this info will look at this truck again now.
thanks,

Richard

 

[kimcrwbr1]

The knock sensor is in front of the starter in the block on a 2,8 not sure on the 2.9. It tells the computer to retard the timing. One way to test it is with a timing light and takes two people make sure the connector is clean first it is usually covered in oily crap. Watch the ignition timing while someone is tapping on the block next to the sensor. Do not tap on the sensor they are real brittle, the timing should retard with the tapping quick taps. The dynamic responce test (goose test) in the KOER test when you get the one flash open the throttle WOT quickly and let off quick if you do it slow you will fail the test. The knock sensor tells the computer when to stop advancing and when to retard ignition timeing.

 

[wildbill23c]

Would putting higher octane fuel in a 2.8L engine cause a knock problem?

 

[RustedRanger]

Higher octane would reduce knocking. Higher octane doesn't mean it burns hotter. Octane is a measure of resistance to detonation (knocking).

 

[Jaelaw89]

Where is the plug for this sensor? I’m in the middle of a rebuild and I found the sensor but I can’t find the plug

 

[bcschief]

Left side of engine in a separate harness with the low oil level sensor 3 wires in the harness. I will look for my evtm manual later for the wire colors. No one makes those sensors anymore and the ones in the salvage yards look like yours ( broken connector).

 

[adsm08]

Where is the plug for this sensor? I’m in the middle of a rebuild and I found the sensor but I can’t find the plug View attachment 49359

If this is your 89, it isn't there. Someone must have put an 86 or 87 engine in the truck at some point since the knock sensor wasn't used on a 2.9 after 87.

 

[Jaelaw89]

Th

If this is your 89, it isn't there. Someone must have put an 86 or 87 engine in the truck at some point since the knock sensor wasn't used on a 2.9 after 87.

Thanks man. I have been trying to figure it out for months. Never even thought the motor may have been swapped.