TNRabbit

I have a 1994 Xtracab 4x4 pickup w/3vze & 5 spd. I've had an intermittent issue with pre-detonation that doesn't seem to be tied to any particular condition (fuel, load, temperature, speed, etc.); perhaps someone has had a similar experience & can shed some light on it.

I will be driving along and suddenly the engine will pre-detonate (knock). It has happened under partial to full load, under practically no load, at both low and high rpms (throughout the rpm range), with all brands/grades of fuel, when cold, when hot, etc. I can floor the throttle at 1500 rpms in 5th gear and it pulls fine all the way up, but other times I can give it partial throttle in 3rd gear @ 2k rpms and it will knock. It has knocked @ 3-4k rpms while accelerating hard in 3rd gear then immediately won't repeat the knock a minute later under the same conditions. It truly seems to "come & go."

Can a knock sensor have an intermittent problem, or does it go completely when it's finished? Could it be a bad contact on the wiring? Any suggestions?

snap-on

i am fairly shure a bad/faulty knock sensor should kick a CEL. but yes there is a FSM procedure for checking the sensor. you might search it out.

TNRabbit

I looked EVERYWHERE on the link to the FSM and couldn't find anything about the knock sensor....???!!?

celica

I would check the wiring to the knock sensor - it can get brittle & break - it could be grounding out causing wierd readings

Saint_Berzerker

Yeah, the fsm has everything but info on a knock sensor...lol.

You would get a code 52 if the knock sensor was bad though...so I doubt that's what it is. Even if the wire was just bad, you'd get a code 52.

When mine went bad, and the code 52 comes on, your timing will retard so much that you NEVER get any knocking, but you get the CEL on. If the ecu doesn't sense the knock sensor, it retards the timing. So, since you get a lot of knock, your timing is not retarding, hence your knock sensor is fine, I think.

So, I would check your timing first. I had a big nightmare over months with the knock sensor. I finally replaced it, and all has been fine since.

^VooDoo^

Check the fuelPressureregulator to.
Also the center contact in the underside of the diss cap.

Guardian_Saint

I also gotten a code 52 which did the retarded timing when it reach 3k rpm but I checked the knock sensor and it appear to be fine but do you guy's mean I have to take out the duct tape out? and so where is the knock sensor ground connect to at? I don't know but they said knock sensor won't cause the truck not to go any faster than 25 mph when that code pop-up, but anyway I'm giong to replace it, it been sitting in the garage for 4 months due to that problem.

TNRabbit

Thanks for all the suggestions!

VooDoo: I'll check those ASAP--thanks!

TNRabbit

Is it possible the dealer put too hot range plugs in on my last trip (plugs replaced @ 156k miles)??