'99 Legacy Outback, knock-sensor code.

[colinrmitchell]

Hello everyone, I'm Colin and new to the forums.

 

My girlfriend has a 1999 Legacy Outback with the 2.5L. It has about 140k miles on it.

 

Recently, we received a code P0325 - Knock Sensor Malfunction. There was an EVAP code which I erased and has yet to reappear.

 

I replaced the knock sensor, and also the wiring to the CPU, and it did not help.

 

I also put in the specified NGK plugs. It has new wires that are about 8 months old. I also checked the primary and secondary resistances on the ignition coil. All to no avail.

 

I disconnected, cleaned, and reconnected several ground wires, and also the battery lugs. I disconnected and checked many other electrical connectors.

 

I sucked half of a can of Sea Foam into the intake, which did make a noticeable improvement. I have put the other half of the can in the gas tank, but have not run more than 1/8th of a tank through the vehicle.

 

Since she has no recollection of it ever being done, I have replaced the timing belt. This seemed to help none.

 

I have a valve ticking, which I am almost sure is from cylinder #1 after checking around with a screw driver up to my ear. I then did a compression test and all cylinders are OK.

 

I also performed a vacuum test at idle with the engine at operating temperature, which read 25"/hg, which seems a little high, according to a Haynes manual. The needle was steady and pretty much stayed there on application of throttle.

 

I am really starting to lose my patience here. I am new to this vehicle, and am more used to working on Rangers. I also do not have much money to randomly replace parts until I strike gold.

 

The code returns immediately upon erasing it. From sight and touch, it appears that the engine is vibrating more at idle than I expect or recall. Sitting in the seat at idle, I notice a vibration above what I would expect. It also seems sluggish and underpowered until it reaches 2500rpm. I do not know where the torque peak is on this engine, so maybe that is all that I am feeling.

 

I am not sure if I should look more into the fuel system, or a possibility of motor mounts. It would be helpful if anyone else may have experience problems with any type of motor, transmission, or torque mounts.

 

I appreciate your help!

Colin.

[Bdubs]

Take a multimeter to the knock sensor harness to see if it's getting any voltage. Something has to be wrong somwhere between the wire and the ECU of the car, if you have replaced the sensor, and it's still throwing the code.

Also, if you feel the car is vibrating a lot, motor mounts would help, and if it is an Auto transmission, try flushing the ATF and using an additive as well. For some reason, the AT cars engine will vibrate a lot more if they haven't had a tranny flush.

[colinrmitchell]

I ran a new wire from the knock sensor directly to the CPU and it didn't help.

 

I also had the knock sensor hooked to the CPU, but sitting on the floor in the cab, and the CEL did not reappear. So I am safe to assume that the knock sensor is OK.

 

The engine does seem to vibrate excessively, especially at idle, comparing it to the engines in my other vehicles.

It is not from a miss-fire, or that bad, just vibrates visibly more than other engines I have observed.

 

I will try the ATF transmission flush. What kind of additive do you suggest?

 

The motor mounts look simple to change, unless there is a bolt hiding somewhere that is not accessible from underneath.

 

Thanks for your help. I'll see how it goes after the flush.

Colin.

[Platinum_Racing]

Perhaps the car is knocking? Higher octane fuel is all it takes to find out, but that would mean a different code altogether.

 

I know the code means a malfunction, which may mean a problem with the ECU, but it's most likely a problem with the wiring. I'd say regardless of the new wiring, get a meter and test the resistance to the sensor.

 

Edit: Don't use any additives to the transmission. Straight up Dexron V, conventional or synthetic. Those sealers/conditioners aren't a good idea, I don't care what the bottle says.

[colinrmitchell]

I put 94 in it and ran it for a few days, that didn't help much.

 

I just flushed the transmission fluid and that didn't help.

 

I looked at the mounts. The motor mounts seem to be pretty solid, but there appears to be excess slop in the transmission mount. If I pry up on the mount, what's about the most acceptable amount that it can move? It seems like I can pry it up over 1/4".

 

The car drives pretty good otherwise.