My954Runner

My check engine light comes on after driving for a while. I checked the code and it comes out to the knock sensor, with either a short or an open in the sensor.

I can turn the key off, and the error resets. It can drive for a while just fine, then the alert comes on again.

When the check engine light comes on, it drives real sluggish, and has a decrease in power.
However, when I reset it, it runs just fine.

I do not hear any knocking from the engine at all.

Can I just replace the knock sensor.

I just had the water pump replaced, and also the bypass hose and pipe.

any help would be great!!!


Chad

snap-on

yes you can just prelace the sensor, thats what i would do but its under the intake plenum, not the easyest sensor to get to. Least it is on my 3vze... you didnt mention what kind you had.

midiwall

Like snap-on says, yes, you can replace the sensor... and fwiw, it's also a bear to get at on the 3.4L.

Also, the reason the engine runs horrible is that when a sensor goes (or the ECU thinks it has) it will go into a safety mode and setup for full timing retard.

You'll find that the sensor is a bit expensive... about $160 for the 3.4L. There are two on the engine, and you can kinda' hack things if you don't want to spend the cash... just wire up the two sensors in parallel. I've been running like this for 6-7 months now and things are "fine". It's not the best thing in the world, but it'll save you the cost and the trouble of having to tear off the plenum, intake manifold, gaskets, fuel rails, etc. just to get to the sensors.

My954Runner

yeah, I know its a bear to get to. I just checked the price at Autozone here, and it is 130.00.

BTW
I have a '95 4runner, 3.0 V6....all stock pretty much. I have added a Delta 40 Flowmaster...........Sounds Cool.....Way better than the stock POS muffler they put on it.....

4mydogs

Mine had the exact same symptoms, but the sensor wasn't bad. Here's my thread:

https://www.yotatech.com/forums/f2/knock-sensor-vacuum-leak-69255/

Perhaps there was a bad connection and when they did the other work they made the connection good? All I know is I haven't had the problem since and I've done about 800 miles.

midiwall

Cool.

Make sure you replace the right one. I made the mistake of replacing the non-broken one and got the enjoyment of pulling it all apart again. Of course, the other one _did_ end up failing _after_ I swapped the sensors. argh. That's when I just hot-wired them and left it.

The specific code should tell you which one is failing.

callmej75

won't it throw a code even with a bad KS wire?

Mudcat

I was getting the KS code too. I had another sensor laying around or you can go to a junk yard and get one. They very seldom go bad usually it's just the wire. I drilled a hole in my left side engine lifting bracket and put the sensor in it and put a nut on it tightened it down and bought a new wire from the dealer $14. Ran the new wire to the knock sensor hooked it up and now no light. Sure beats removing the plenum and intake again. Just another idea for those on a budget. I know of a few running around like this for several years.

midiwall

Hmmm... I wonder if a knock will be loud enough at that point to be detected by the ECU?

A knock sensor is just a piezo microphone, and while the mic element itself is pretty sensitive, the ECU will be calibrated to look for a certain voltage level coming from it to register a "knock".

So if you move the mic element away from the designated spot, you're effectively disrupting the calibration of the ECU/KS pair.

Just a thought... Great idea though!

ChickenLover

3VZE knock sensor. Not a small job.










It's all the way under the intake manifold. Before removing the intake manifold you better remove your timing cover and clamp the timing belt to the cam pulleys. The #2 idler pulley will be removed with the intake manifold and it acts as a timing belt tensioner. If your belt slips or skips teeth on your cam pulleys, you will have a real headache.

Toysrme

Werd. 90% of the time it's the wiring. However, sometimes they do go bad. If there is continuity between the terminal & the housing/block, It's shorting out. In which case it must be replaced.




Knock sensors are a pain in the ass to get off the block. I did one of mine last week on my 3vz-fe & gave up. I finally resorted to pulling out the dremel witha cutting wheel & just cut the threaded housing into 2 pieces to rip it off LoL!

My954Runner

Where does the wire from the sensor hook up? I would rather not take the engine aparte AGAIN, I just had the other stuff done 3 months ago. Hooking up another sensor sounds good to me for now.......DUmb-A$$ me should have replaced it and the sensor when I had the other stuff done, but I was already getting hit with a $700 bill that was unexpected.............

Thanks

Chad

Mudcat

To replace the wire you must remove the plenum and intake manifold. I will leave mine like it is until I need to remove some of the parts for some other reason. I would think there is a threaded hole in the block or head that you could use too but the wire length limits placement.
The lift hook works for me.

My954Runner

Can someone tell me where the know sensor wire hooks up to the harness?
I am getting a new wire and sensor to hook up until I need to take the engine apart again.

Pics would be great also....

Thanks

midiwall

ChickenLover posted a pic above... does that help?

I can only be direct help on the 3.4L...

Bassinfool

It hooks up right underneath the TPS. My CEL was blinking a knock sensor, but when I took everything apart, the wire was just chewed up. New 11.00 wire, and no more problems.

Dave Mooney

Mudcat or others: If I choose to go this route what difference in performance will I realize by hooking up a "false" knock sensor until I want need to back down uder the plenium and intake again for another reason at the same time?
Currently the 94 4Runner 3.0 slo seems to be running fine even with the code 52 knock sensor check light on. doesn't appear sluggish to me. Is there anyway it could run as normal in safe mode?

midiwall

When my knock sensor died, I never realized how big the performance hit was 'cause I wasn't really looking for it. Ya' know? It was one of those things that I'd notice the truck "ran different" or "the RPM would come up" if I cleared the code while driving, but I didn't really feel an overall performance hit.

But it was there... Once I realized that the ECU would go into full-retard when I threw the code, then it was easy to pick up the before/after changes.

I dunno about the 3.0, but I think the 3.4 ECU will push a 15* retard across the board when it sees a knock sensor fail. In hindsight, that's a LOT, and if I force that kind of a retard now, it's VERY noticable.

Dave Mooney

Is this something I could verify with my timing light. I have one and would like to learn more. If I can get better performance I owe it to my daughter, it's her car. Thanks. Can I put the check the timing while reving the engtne and see how far the mark on the crankshaft pulley goes below 8 degrees above top dead center?

Dave Mooney

How do I claear the code while driving. I would like to try that and see if the rpms change? Sounds like a way to confirm my loss of power.