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.

 

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

 

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.

 

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

 

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.

 

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

 

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.

 

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.

 

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