P0325 on a 99 Forester "running on two cylinders"

You have the knock sensor. If it is an easy access to take out the old and put in the new one - hey, it’s worth a shot. I don’t give it a high probability of success, but if the effort isn’t much then what harm can it do. Some knock sensors are easy, and some are a bear - hopefully this is one of the easy ones. Good luck.

I have watched some videos and the guy in the forums described it. You find the white plug on top of the engine and follow it down to a black donut shape with a bolt through the middle. Remove the bolt, disconnect the cable, put your new sensor in the same position as the old one, tighten it to 17 foot-pounds, and connect the cable.

I’m having a hard time seeing a knock sensor causing a misfire at idle on 1 and 3.
What would I do if I were in your shoes?
I’d run a compression test and make sure the numbers on those 2 cylinders are good. Ideally, you would be looking for 175 PSI and up. Always make sure the basic engine is mechanically solid before chasing other gremlins and I mention this because of the valve adjustment referenced previously.
If the numbers are good, then I would connect a vacuum gauge to determine if there are any vacuum leaks.

The point about a vacuum leak is that it can cause poor running at idle that smooths out when revved.
It is possible for a Subaru engine to suffer on one side and not the other because of a vacuum leak combined with the design of the intake manifold and boxer style engine.

Aww, but I just put the spark plugs in there!

Just kidding. This looks like one of those things where purchasing the tool can cost less than paying a shop to use theirs, like my OBD-II reader. I paid the first shop $100 and the second $45 to diagnose my check engine light and I do not know that they did more than disconnect my Ultragauge, which reads codes, to plug in their code reader.

Well, I will replace the knock sensor, since I already have that, and if I still have a problem, I will do a compression test. That seems simple enough. Thanks!

By the way, I asked my friends, and they say their batteries last two years or less. Also, I do not know why I thought there was only one Subaru dealership in the Phoenix Metro area, unless it was when I went to order parts. Subaru’s website shows Peoria and Tucson, then Las Vegas and St. George, Utah. However, there are two dealerships that are closer to the one in Peoria, although they do not have an on-line parts inventory, you need to send a part quote request.

I replaced the knock sensor, but it is not running any better. I was researching vacuum leaks and bad coilpacks, but just went out, removed a spark plug wire, and bridged the gap between my engine block and the connector, creating a spark.

Still no engine codes, though. I just went and drove. After about twenty-five miles, my check engine light came on, but went out after a little while. I honestly believe that was the time that it gave me P0301, P0303, and P0304.

I was not driving fifty-five miles an hour, down the highway, on one cylinder!

The check engine light came and went a few times, each time but that once giving me cylinders one and three. I just want to take it to a Subaru dealership and let them deal with it!

Some guy at O’Reilly said that he had two Subarus and he always took them to a nearby shop, so I may do that, but I really wish that I could focus on school.

By continuing to drive the car when it is running so poorly you are just making things worse. You are putting more unburned exhaust gases into the cat and it will overheat at best and at worst you could kill the cat completely. Then, you’ve got even more money to shell out.

Take the car to a competent Subaru specialty shop, or a Subaru dealer - leave it there and focus on school. Part of your overall education is to know when to ask for help. In this case you are not skilled and knowledgeable enough to diagnose this problem and fix it. You are just wasting your time and your money.

Okay guys, thank you for your input. I took my car back to the shop that replaced the timing belt and asked them to make sure that it was still on right. They said that the tensioner had been faulty, so they replaced it. I just got my car back and it is driving smoothly again. The knock sensor had been bad, but either the mechanics did my timing belt wrong, or they used faulty parts. Hopefully that is the end of all of this.

Thanks again and good luck.


I just looked at your original post again.

I am hoping that your “service plan” covered the expenses

Definition of “faulty tensioner”; - Feed you a line of BS as a face-saving move because we screwed up.
It’s part of the Mollification Program… :slight_smile: