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My (now my daughter's) '92 NA 4EAT wagon started pinging pretty badly on the trip from Tacoma to San Antonio this past week. I also had #1 injector failing (miss at idle, okay once up and running). I've replaced the injectors and it runs much better, but still rattles/pings under light to mediam load.

Could this be a failed knock sensor, or do I have something else going on?

On the good side, I got an average of over 31 MPG over 2300 miles running between 65 and 75 most of the way. Several legs were over 32 mpg, but I was running 300 miles either non-stop or with just one stop to use the bathroom.

just pulled it to check and it is cracked... Autozone $44.95

Anyone have an opinion on whether this will fix the knock??

Well,
I changed the knock sensor and that seems to have fixed it!!! Seems like it has a little less git up and go right off idle, but if it was overadvancing the timing that would make sense

yea those knock sensors go bad all the time. they are notorious for that crack.

Good that the symptom is fixed.
You might also check o2 sensor function and fuel pressure.

Keep an eye on your coolant level and temp gauge as well. I had a '91 that would knock under load and it was a blown headgasket. Didn't figure it out until the car started heating up and I figured out the HG was literally overpressuring the coolant system and blowing the coolant out. Kicker was it would only do it under a load so the quick trip wouldn't cause any problems, it only happened when driving up hills.

Did you have a CEL on the knock sensor? If so, did you clear the ECU after replacing it?

Okay to answer everything:

1. No coolant loss or overheat on a 2300 mile trip (Tacoma to San Antonio in 3 days) - Temp gauge never moved above normal even on the hard climbs in the passes

2. No CEL, that's one of the reasons I posted to get opinions

3. I'm back in Tacoma now, so hard to check fuel press or O2, but no CEL, and 32 MPG average for the trip...

4. Knock sensor WAS cracked and gapped open, and I had an injector starting to go, miss at idle, was getting worse at the end of the trip (replaced all 4 injectors with re-man's, idle is smooth again)


It was runninig good again when I left it, will stay in touch with my daughter and make sure it stays fixed...I thought about changing the O2 sensor, but it's running well, so I'll wait and see how it does. O2 is easy enough to replace, her granddad will be able to change it if needed.

Thanks for all the input.

did you end up using an oem knock sensor

32mpg makes me think it was running lean. Hopefully the injectors fixed it.

Injectors did help, but it still rattled after changing them. used an Autozone knock sensor, didn't have time to order a Subie factory part. Had to get back to T-town for work.

I figure with the #1 injector starting to fail (or plug) that the ECU probably added fuel across the board to compensate based on the O2 sensor reading, but #1 would still have been lean.

beatersubi wrote:32mpg makes me think it was running lean. Hopefully the injectors fixed it.

My AWD '90 w/4.10 gears gets 28-29 on long hiway runs with a couple of stops, so I didn't think 32 for a FWD 3.9 geared car was out of the question... I tracked each tank, and the worst was 28.8 after the gasstation monkey in Pendleton short filled me. Every other tank was between 31.8 and 33.1, tracked over 2300 miles.

Missed the fwd part. Enticing fuel milage.
Any other luck tracking the source of the knock?

Swapped the knock sensor (as above) and seems to have taken care of it. Talked to my Daughter this evening, and she got the inspection and tabs done, and is driving it to school and work. Said no rattle/knock and idling better than it was when I left, so the computer is re-learing all the new parts..