cjserio

So I recently bought a truck that was constantly throwing the infamous Code 52 (Knock Sensor). Like everyone else, I assumed it was the pigtail and set off to remove the plenum and intake to change the $20 part and get the engine up and running smoothly again. Well, when I finally got the intake off, I found that some mice had built a nice little nest under the intake and apparently didn't feel that my knock sensor matched their decor so they chewed the wire off....

I do have a serious question though...I had to take the idler pulley off to lift the intake. Before doing so, I drew a mark on the timing belt and tooth on each cam. When I lifted the idler pulley out, the timing belt obviously became very loose. Is it safe to just line up my marks again when I reinstall the idler pulley or should I be worried that some teeth are off way down on the crank now or elsewhere? I've tried not to move the belt very much to avoid making matters worse.



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TNRabbit

You're going to have to re-check your valve timing. Not much of a way around it. There are several threads on here of what to do/not do. I've written several myself. Read before you start doing it!

cjserio

Yeah I screwed up. I've been meticulous all weekend getting the intake and plenum off but I got hasty at the end of it all....sadly it was the part that required the most attention to detail.

shaeff

The way I've always gone about doing stuff like this, is to set the motor to 0° Top Dead Center before removing the timing belt. That way, all you've got to do is set everything at 0°, slap the belt on, and your base timing is set.

scope103

Better yet, get a new belt. Since the truck is new to you, you don't know how old the timing belt is, and there's no point waiting for it to break.

The only slightly difficult part is that you will now need to remove the harmonic balancer to get the belt off the lower pulley. The crankshaft bolt is spec'd at 181 ftlbs, so you're going to need to resist a lot of torque to remove the bolt (otherwise you just turn the crankshaft). There are about a dozen distinct ways to do that, but don't forget that you will need to put that bolt back in and torque it up. So before you try a method that will get it off (starter?) but not back on, think about building a simple tool. There are lots of very good ones on this list; I'm partial to https://www.yotatech.com/forums/f116.../#post50756358

Of course, you can go to town now that you're in there and replace the timing idler pulleys and the water pump, but that's up to you.

cjserio

Yeah I might just do that. The last one was replaced at 96,000 miles (it currently has 166,000 on the truck) so it's getting close to the end of it's life anyway. I've read dozens of articles on doing the job and what I don't understand is why I can't just put the truck in 5th gear and 4L or something since i have a manual transmission. Is 181ft-lbs that much torque that i'd still turn the wheels?!?

scope103

I don't know (I have an automatic), but several folks on this site have reported success with that method. Do make sure you have the parking brake pulled up tight, and you might want chocks on the front wheels.

shaeff

And if you start walking the truck, you could always have someone stand on the brakes as well.

Team420

thats not really that unusual a cause... I have pulled several intake plenums on 3vze's, and I'd say about 80% of them had a nest under there....

oldblue

not sure why, but mice LOVE chewing on knock sensor wiring. I've probobly done 20 knock sensor wiring harneses on the late model honda v6's, always have a kncok sensor code due to rat damage. strange.

coopster

I wondered that myself. My 94 had some sort of feed pellets, but no nest. The 95 had the nest. Can't figure out HITH they get in there, either.

cjserio

Wow so i guess it's not that unusual after all. I just expected a brittle wire when I got the intake off. I'm kind of happy to see this nest and chewed wire. At least now I feel like the teardown wasn't a waste of time.

cjserio

I got the intake back on and put in the new idler using my handmade marks that i drew on the belt and cams before i disassembled....I turned the engine until the notch on the harmonic balancer was at 0deg on the plate. Both cam notches lined up perfectly even after a couple of rotations so I guess I'm a lucky SOB that nothing slipped even though the belt lost tension in the process.

I have all the parts for a new timing belt but it looks like I can save that for another rainy day.

buel09

Does the intake have a certain bolt pattern ?

Davidjross

guess u guys are the ones to ask. Just bought 90 4runner. The engine check light comes on when I hit the gas. Friend checked code. Code 53. Knock Sensor. Read a lot of horror stories. Does the code mean take off intake? I am told cant smog with light on. Got temp sticker til end of month. Is this going to cost me a fortune to smog? help

Davidjross

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93toyrunner2

Try the "Search" button at the top right of the page, it will produce hours of reading enjoyment with all the answers to your questions. Downloading the FSM (Factory Manual) would be another great place to start reading. See the link in my signature.
Have you read the forum rules for new members yet??

sb5walker

It helps to let us know what motor you have when you're asking for tech help with it.

Code 53 is actually a code for a bad knock sensor circuit in the ECM (computer). It's the 52 that's the code for a bad sensor, or wiring (or mice, lol). So if you're really getting a 53, you may have an issue with your computer.

One thing you can try is to clear the codes by pulling the EFI fuse (in fuse/relay block on passenger inner fender) for a minute or so, and see if the codes come back. Sometimes codes appear for mysterious reasons and don't recur. If you do that before your drive to the smog check, that might squeak you by, but if it is a recurring condition, the code might come back pretty quick.

If code 53 does come back, you might pull the passenger kick panel, pull the ECM, and open it up to see if it contains water, or corrosion, or any burnt components. I see that the knock sensor circuit in the ECM can contain a "filter" and shows an active bandpass filter using an op amp. The filter is required if the knock sensor is the "mass" type as opposed to the "resonance" type. I don't know which our series trucks use, but it's probably the "mass" type which requires the filter in the ECM. An active bandpass filter like the one shown in the schematic usually contains a couple of capacitors, and caps are usually the first components to go in any electronics. You might be able to get the caps replaced at an electronics repair shop, or check for any HAM operators/shops in your area. Most HAMs would probably be able to do the fix.

ECM knock sensor circuit on page 32: http://www.autoshop101.com/forms/h24.pdf

Info on active filters:
http://en.wikipedia.org/wiki/Active_filter
http://en.wikipedia.org/wiki/Operational_amplifier
http://www.swarthmore.edu/NatSci/ech...d/Filters.html

22re diagnostics: http://personal.utulsa.edu/~nathan-b...26diagnosi.pdf
3vze diagnostics: http://personal.utulsa.edu/~nathan-b...85diagnosi.pdf

shaeff

^Great post