Annoying tapping!
 

Hi, My dad recently gave me one of his 4runners :rockin: ... it is a 1992 toyota 4runner SR5, with the 3.0 3vze V6 motor...it has an automatic tranny, and some mods done to it... it has a motor from a 1992 toyota 4x4 pickup in it... now when the truck is running, and you let off of the gas, there is an annoying tapping coming from the motor... :bang: we've put a stethoscope on the oil pan, and it doesn't sound like it's coming from there... you can hear it a little in the exhaust note, but you can't hear it in the valve covers (Cam covers...sorry...lol)...Im thinking it's maybe a bent valve or something... ever hear of that??? also I put thicker oil in it (20w50) and it got quieter... but we've changed the rod bearings in it, so the only possible bearing it could be is the mains... but I don't think they would make this sound... and it doesn't hurt the truck's performance, or reliability.. it's just an annoying sound... i've had it to almost 4500 rpm, and no problems... the thing flys... but that sound is there when you let off the gas...if all else fails we have 3 spare motors sitting in my garage(Just in case...lol)... any Ideas of what it might be??? also you can hear the sound best if you stand right next to the driver's side door... weird...

Thanks for all your help!!!
Steven...

fuel injector ticking?

I know mine are pretty noisy. I also developed a slight exhaust leak, but mines the oppisite louder when I give it gas, quieter when I let up.

I have a '94 xtracab 4x4 and it has a ticking sound that I believe is from the injectors; sometimes it isn't there but most of the time it is. It hasn't seemed to matter because I've put 110k miles on it since 2000 and it runs great.

valve adjustment maybe? putting thicker oil in wouldnt quiet down injectors...

I tend to agree with yota krazy... A valve adjustment can only help, and you won't spend any cash unless you get new gaskets for the covers. Just check on what the adjustment should be at and make sure to torque everything back down to spec.

Could have a bent rod, mine did the same thing, and when i got water in my intake, after clearing the water and getting it started the noise was more obvious and vibrated harder, and i was told it was a bent rod.

If you could describe the exact sound or post a sound file of the tick/clack/click/whatever, someone may be able to give you a better idea...

its hard to describe.... it sounds to me like a connecting rod... but that's just me... but it's not coming from the pan.... I will try adjusting the valves...hopefully that's all it is... I had it to 5000 rpm last night... just seeing if it would give... and I actually think it runs better now... lol... it almost sounds like metal hitting metal... another reason I thought a valve... but still not sure... I'll see if I can get a sound clip of it...

Thanks!!!
Steven...

here is a sound clip of the infernal tapping sound... listen closely... it bugs me... lol...thanks!!!

http://media.putfile.com/weird-motor...Toyota-4Runner

Steven...

TRY (it seems hokey, but it has worked great until we have time for rebuilds on the motors in some of our daily driven race/track cars) changing oil, and going with oil one wieght thicker than you usually run, but only add 4 quarts, the 5th quart put Automatic Transmission fluid, which thins your oil badly, but thats why you use the thicker oil, and it will quiet all sorts of noises out of your valves and rods. Try it Good luck...chris

well at this point, I have Castrol GTX 20w50 in it with half a bottle of Bardahl's No-Smoke... I used that because it is the thickest product I could find... and it is proved by the "Bubble Test"... lol...

I listened to the sound file; have you ruled out the A/C compressor, alternator & idler pulley for the A/C? Disconnect all the belts & see if you still hear it.....

If that doesn't work, I'd check the idler pulley under the timing cover.

yeah also check the exhaust reed valve thingy....when I had my intake hoses off it would make a gargling sound where you are hearing the clacking...

I'm agreeing with the previous 2 posts. Doesn't seem to be anything internal to me. At least like a Rod, Crank, Piston, Valves. It sounds like something external. To me it almost sounds like a belt slapping around.

Does your Runner have an automatic tensioner for the timing belt?

also check the 4 nuts that secure the fan to the fan clutch...mine were loose and it made a wierd arse noise that I couldnt put my finger on for about 2 hours...

ok, I will try these things.... I'm not sure about the tensioner... my dad built the motor, honestly I'm kinda new to the "Toyota Thing"... lol...but so far I like it, the truck is almost fast, and it pulls like crazy... so, it might be a keeper if I can figure out that sound... thanks for all your help so far!!!

Steven..

Is the sound noticeable more from inside the cab? I ask because the steering shaft seal WILL be broken on the fire wall. On 3vze trucks it will sound like a clicking/ticking most often mis-diagnosed as an exhaust leak.

I second the reed valve, mine began to make a rattle like sound when you'd let off the gas.

Nevermind the inside cab thing, I just listened to the sound clip. I would check the reed valve but also possibly sounds like an exhaust shield.

The dead giveaway this isn't an internal engine problem is that you get the rattle at specific RPMs, mostly when the engine is on it's way back DOWN from up in the range....reed valve is a good possibility, but I still think it's bearings going bad on an external piece....good luck!

problem is, if it was external, putting thicker oil in would not have quieted the sound. if you are very positive the thicker oil helped, then its definitely internal. how long ago did you do the bearings(rods only im assuming?) and, did you machine the crank throws? is there any difference in the sound from engine cold to engine warm? try using the stethoscope on the block itself, between the cylinder barrels where the mains are. rod knock noise direct path is through the crank throws, to the mains. if you listen where the all the mains are (listen both sides) and you pinpoint 2 mains louder than the others, you found it. it could be a broken or collapsed piston skirt as well, which makes noise, but usually is not fatal. when my rod knock first started, it was rpm specific, and it only did it when off load(de-accel, or very light steady rpm cruise, like lifting going through corner, and very lightly get on the gas it would do it) its gotten so bad now that I: 1, don't drive it, 2 it sounds like the predator coming down the street! (that sound it would make right before it kills someone, a rattling kinda locust sound, sometimes the rig does it very well!)