Karlton

It's hard to tell the timbre of the tapping from the sound clip, but I can say that the manner in which the sound appears is somewhat similar to what I was experiencing with my engine.

Hopefully this is not the case with your engine.

In my case the knocking sound was never on load or at idle. If I was accelerating I could keep it from knocking by shifting between gears quickly and then getting into a higher gear and cruise keeping the revs low.

My knock would appear between a certain RPMs, either when winding down between casual gear shifts, or when I was cruising at part throttle within that particular RPM range. This was a problem at highway speeds, since cruising at 60-70 miles per hour at part throttle would be right where the knocking was at it's worst.

Idling in the driveway, I could pop the hood and manipulate the throttle by hand and get the knock to occur ... never when revving up, always when revving down or holding at constant high RPM.

If anything, I hope this info helps you determine rod knock is NOT your current issue, since rod knock sucks.

Good luck!

4Runner J

My engine has developed a louder knocking sound. My mechanic called it piston slap. My symptoms are almost exactly like Karlton's. I have a '91 4Runner with the 3VZE engine. I am getting a metallic rattle at part throttle. It is occurring at RPMs anywhere from about 1750-2750, but only under partial throttle. Not at idle and not under significant load. Even decelerating off throttle from 3000-2000, it rarely makes a sound. Does this sound like a rod bearing to you guys? If so, what is parts and labor worth on a job like that?

toyota4x4907

Those are for the ADD....

EGR filter housing and modulator.

Karlton

4RunnerJ, it's hard to say. Your mechanic has diagnosed it as 'piston slap' ... which could be caused by a worn cylinder bore which results in the sides of the piston slapping the sides of the cylinder wall.

In my case the sides of my cylinder walls were in good shape, despite the spun rod bearing, but my crankshaft had to have the rod journals reground and I had new wrist pin bushings pressed in by the guys at the machine shop. I'm not familiar with the 3VZE and what it would cost to rebuild or replace one, but for whatever it's worth, my local independent (who I trust) wanted more than my little old truck was worth to replace my engine with a rebuilt ... over $3k. So that led me to go ahead rebuild my 22re with the help of Yotatech.

If you do have a bad rod bearing and it spins, the oil hole will no longer line up with the connecting rod and the already bad bearing will be starved of oil, accelerating it's deterioration ... which also means fine metallic particles in your oil. That's a downer.

If you have the time and inclination you could drain the used oil and check it for metallic particles. Cut open your used oil filter with some snips and check for an excessive amount of fine metallic particles. When I cut open my oil filter it was full of metallic particles and under a light it looked like metallic paint! Left unchecked, the filter could quickly clog and blow the pressure relief valve, sending metallic particles throughout your engine.

Good luck!

xxxtreme22r

Just went through a rod knock with mine, heres the deal, did it only slightly at idle, however if no load and i revved the motor maybe 1/4 throttle I'd get it, and then again while driving it seemed to do it at high rev and mid rev when coming off the gas to lets say shift from 1st to second and again from 2nd to third. or constant speed and lift the throttle a little. Could possibly be a main bearing starting to go as well, specifically the middle main.

pitviper33

Ugh. That sounds pretty familiar. How long did it last like that? Spin a bearing in the end? Did you rebuild it?

xxxtreme22r

Spun a bearing, fused 1/2 of the bearing to the rod and mostly crank. toasted the rod and crank. Neither savable in my opinion. Lasted over 5000 miles like that with the knock. In the process of rebuilding now.

skinnadoor

It sure sounds like my engine did after my timing chain was done on my engine... Man that sure sounds like the valve cover... after listening it to half dozen times... The only difference is, myne was constant becasue it was on so damn tight. You did say it got a little quieter after your adjustments ? If So your on the right track with the cover. In my case, the back 2 bolts holding on the cover seemed to cause the most noise, and ironicly the noise didn't sound like it was comming from that area, but in reality it was.

Did you just back off the nuts on the valve cover or did you pop the cover off then re-seat and retorque it ? I only ask becasue after backing myne off, it got better, but after reseating the cover it dissapeard all together.

pitviper33

Good idea. I didn't pop mine all the way off. I don't think mine were as tight in the first place as you described yours, but they were tighter than 40inlbf. Tonight it'll come off and go back on. Fingers crossed.

4Runner J

Thanks for the info Karlton. Seeing as I too have a truck that is not worth paying for a rebuild, I will probably just drive it until it dies and then part it out and get a newer Runner.

pitviper33

Well I hit a deer with my car, so the truck has been my main transport while it's in the shop. That hasn't put me in a spot where I feel very comfortable digging into it very far in the evenings. However, this morning I did pull off the valve cover bolts, lift the cover, then torque them back down to 40inlbf. Tapping is still there. I was really hopeful we could come up with some explanation other than rod knock. It's not looking (sounding) good right now.

pitviper33

Here's an update: Last night I replaced the valve cover gasket and the washers on top. For 21$ it was worth trying. Well it didn't make the noise go away. Nope. I'm about out of options other than rod knock.

pitviper33

For the sake of anybody still following this or having a similar problem, here's another update:

I tried some STP oil treatment. I know that stuff should never be necessary if your engine's in good shape, but I wanted to see what would happen. Well it quieted the tapping down a little. Not good. After driving a couple hundred miles it was as loud as before. Not good at all.

I pulled it into the garage and got down to business. I tried listening with a stethoscope while revving by hand to make the noise. It sounded like it was coming from around cylinder 1, but I still couldn't discern top of engine or bottom of engine. I drained the oil, dropped the front differential from its mounts (left axles connected), and wrestled the oil pan off. I pulled the rod cap from #1, and sure enough, there's the problem. The bearing is toast. It's down to the brass all the way around, and there are a couple chunks missing. The crank journal has some marks but is smooth to the touch. I mic'd it, and the diameter is within the range in the FSM. So I decided I'm leaving the crank alone and installed. I ordered some new rod and main bearings, and the plan is to change them with the crank in the engine and the engine in the truck.

Any tips for this job are appreciated, and I'll try to give another update when things move forward. Wish me luck!

pitviper33

Well the last three posts were mine, so I'm not sure whether anybody else is following this anymore...

If you are, I have a question. Are the rods numbered in any way from the factory? The two rod caps I've pulled off both have numbers on them. Neither of them is on the cylinder its number would suggest. It has me questioning if this engine has been rebuilt before. If it was, did they put the rods in the wrong places (not a big deal), or did they put the rods in the right places and the caps on the wrong rods (big deal)? If the caps are in the wrong places, that could be a reason for mine to fail the way it did. So is there a way for me to pull the rod down and find a number? Maybe I can reach up in there and feel the number? I'd like to try.

Thanks!

xxxtreme22r

Mine were the same way, they are not numbered from the factory. you should number then as they are taken off. rod and cap. the mains you will notice are numbered 1-5. Not sure what those number nean but it confused me too. take notice that each side of the rods/bearings there is a little nipple on one side and not on the other. the niples face forward and have to go back on that way. on the mains you will notice that there are little what look like trees, they point forward was well.

karlster

I had the same problem in my 92 22re pickup since new. Anytime I would be rolling at a steady speed and slightly back off on the throttle I would hear a rattling/tapping noise. If I was going over 30 or 40 miles per hour there was usually enough road noise I wouldn't hear it though.

I took it to a mechanic who claimed he didn't hear it. I figured I would just live with it. At 150k miles I got my timing chain replaced by a non toyota specific mechanic. It rattled as bad as ever and when I took him for a ride to demonstrate it he claimed it was piston slap but not to worry as the truck would run forever like that.

Eventually I found a recommendation online to a local Toyota specialist (Santa Cruz import truck repair), family run business (dad, son and mom) that knows these trucks inside and out.

The owner said it was a rare thing but on occassion he had found a bit of paper (possibly from the oil filter element) clogging the orifice in the timing belt tensioner that applies oil pressure to it.

I told him to go ahead and check it out. That evening he called to say that , sure enough the orifice was blocked preventing proper chain tensioning.

Ever since then it has been fine. The bad news is you pay a lot of labor to have the front of the engine torn apart to repair this but it cant be good if the chain is fluttering around due to inadequate tension.

Good Luck,
Karl

pitviper33

I thought I should give one final update here. I went through with it and replaced the rod and main bearings (they came in a kit together from engnblder.com, so why not replace the mains at the same time?). The noise is now totally gone. I can't get it to make it at all. The bearing replacement job was pretty simple. It's a little time consuming, but you could have it finished in a day pretty comfortably if you had the parts in hand.

So if you hear a noise like my sound clip posted earlier in this thread, it might be rod knock. Replacing the rod and main bearings fixed it for me.

92 TOY

I'm marking this thread since it's full of alot of trouble-shooting info. Good job on figuring out the problem.

1styota4X4

I am fighting the same demon. I am going to pull the pan and replace the rod bearings and see if that helps. if not i am going to start the rebuild of the motor. Already priced out through enginbuilder great prices Im gonna get a new head as well with a cam...Mine fits your exact description and has slowly gotten worse over the last 6-8 weeks. I to thought it was piston slap till it slowly got worse. I even have the timing chain kit as that was next on the list. I will keep you posted and let you know what I come up with.

Jeremy11

I had the rod knocking problem also.. I bought my 1990 4runner for 500 bucks considering its owner didnt know how much it would cost to fix the "noise" which was a rod knocking. Turns out 5 of my rods were burnt so i ended up replacin my whole crank kit all 6 rods and a new oil pump etc. just in case that was why they were burnt. It fixed the rod knocking sound but now i have another "tapping" sound which i dont know what is causing it.. it starts as soon as i turn on my truck. and it taps all the time and gets more definite while im driving. I have a 3.0 V6 in my 199 4x4 automatic Toyota 4runner. Any help is appreciated