Knock Sensor

2000 Mercury Villager. The engine is missing pretty good. RPM’s go up and then they snap back and no real acceleration. I took it to O’Reilly’s and had them put the code reader on it and it came out as a defective knock sensor. But through all this the check engine light has never come on.

Replacing a knock sensor is an expensive fix on this van because you have to take the manifold off so I was looking for any advice on whether it could be something else.

I’ve put two cans of heet in the gas, replaced the spark plug wires and 4 of the 6 spark plugs. I’ll replace the other two but just ran out of time.

Any suggestions?


Exactly what was the code?
The reason I ask is that a knock sensor detects the vibrations of other problems, specifically those that cause preignition.

I’ll have to go back and see. Which is no problem.

Nissan V6 engines of this era have problems with the knock sensor and wiring harness, which is located under the intake manifold. (You know your van is a rebadged Nissan, right?) This code will usually not turn on the engine light, and I seriously doubt it’s the cause of your problems. I’m almost sure it’s something else. But I’m afraid it’s going to require more information about what’s going on with the engine, more info than a free code read can give us.

If it in fact is misfiring you should be able to determine which cylinder is misfiring by pulling spark plug wires one by one and find out which one doesn’t make the car run worse. That’s your dead cylinder.

So is there any subtle engine rattling going on when the engine is fully warmed up? If so, maybe the problem is in the EGR system.

The knock sensor and the ECM can only do so much and if the rattling is bad enough the ECM may not retard the timing enough to offset it.
It’s also quite possible for an EGR problem to exist with no codes being set; usually a clogged or partially clogged passageway.

The code is P0325.

Also to a point I see made here it drives perfectly fine for the first few miles of driving. And then the issue starts. So I guess it starts once the engine is warmed up.

And once your in the higher couple of gears there doesn’t seem to be any problems. Just while your trying to accelerate getting from 0 to about 40. Chugging is the best word I can find to describe it. Any other questions let me know.


Code P0325 is for a circuit malfunction to the knock sensor. The wiring to the sensor needs to be checked out for a problem before blaming the sensor itself. I agree with @OK4450, clean or replace the EGR valve.

Working on this again today. To anybody that knows the car is it possible to check the wiring without having to do all the similar work it would take to get to the knock sensor itself? I’m hoping the harness is accessible. I’m looking for pictures and diagram on line but thought I’d ask as well.