ShadowTek

I have an '88, 22re, 5 speed, 4wd, truck. Today I noticed a sort of engine knock that only occurs every few seconds. It seems erratic and doesn't seem to occur at a regular pattern. It doesn't sound like it's affected much by pulling the throttle, but I can't really tell over the engine noise.

The noise only seems to start about a minute after starting the truck.

Anybody have any idea what could cause a knock like this?

Another issue with this truck is bucking when I first put it into gear. I haven't traced that problem yet, so I don't know if it might be related.

JasonYota

iTrader: (1)

Does the noise happen while driving or just sitting idling? Is it coming from the engine compartment? Look for anything loose that's where I would start. It could be many things

ShadowTek

I can't actually hear it from in the cab, so I can't tell when I'm driving. I can only hear it with the hood up, or it's just as noticeable from under the truck.

I runs strong, and I can't feel any lack of power or missing when I'm driving.

I tried pushing on a few things here and there to see if i could find anything loose, but I couldn't make any difference like that.

JasonYota

iTrader: (1)

Interested to find out what it is. With a vehicle that old it could be anything.

Flash319

I have found that most erratic noises from 22re is a usually a timing chain (tensioner) issue. Pull the valve cover and have a look. See if your guides are broken. Also piston slap on these engines is somewhat normal, but that would be regular not erratic and more when cold.

yota81

Timing chain, valves make a good bit of noise (but in a rhythmic manner) and piston slap is common...these old tractor motors are not the smoothest or quietest

ShadowTek

Today it seems to be a more regular rhythm, like once or twice a second.

I've taken the valve cover off. None of the rockers were loose, but about half had no clearance at all.

By the guides, I guess you mean the things just below the camshaft on either side? They look metal, and the chain had no slack.

I won't have it back together today, and I broke one of the stupid plastic sleeves that a vacuum hose slides over, so I'll have to fix that too.

ShadowTek

I adjusted the valves to spec, and the engine seems to run smoother now, but the odd knock is still there. I held a stethoscope to the valve cover and then the oil pan, but all I heard was a steady rhythm. I couldn't find anything with the stethoscope that returned that knock.

ShadowTek

HA! Three years later and I finally solved the mystery!
The nut on the alternator pivot bolt had loosened up just enough to allow the alternator to rattle back and forth. I didn't realize it until I shined a flashlight on it and I could see it barely wiggling.
The crazy thing is that is sounded like all the racket was coming from back around the firewall, the way the sound was carrying.
I added some low-strength loctite and tightened the nut back down and the sound is completely gone.
FINALLY! lmao