I get a knock from the engine between 2500RPM and 4000 that only occurs under load when accelerating or when blipping the gas a little. Sounds like it's coming from the top of the engine. I suspect a valve issue. Has anyone had this problem and figured it out? It runs OK except for a cold start issue and for some reason when the engine is warm and has been shut off, then restarted, it will idle low and act like it wants to die, that might be a TPS issue because it started to do that after I replaced the TPS. Idle is a little rough but not too bad; exhaust seems to have a little puff to it every now and then. I also have low compression in #4 cylinder but only by 60psi. and is still over 100. I'm trying seafoam right now and has improved a bit but not enough. I still haven't done the seafoam in the PCV valve yet.

 

Since it seems to only be while you accelerate it is probably not a rocker arm issue.
Back when I had an olds cultass V6 I got the same knocking and the same symptoms, but only it was right from the start.

Head gaskets good, maybe the minor psi drop might be the problem.

 

bad bearing. sorry.

 

I think if it were bearings, I would know it and would hear the knock all the time and more towards the oil pan area. The sound is clearly coming from the top of the engine. #4 cylinder which is the one with low compression. When extra oil was added after the oil was added for the ring test, the psi. jumped 10psi. on the compression test. Most mechanics have told me that it was a valve/head issue when they heard that. The truck would idle and blow gobs of black smoke for a while, then once that cleared up, on deceleration, the engine would blow blue smoke but after a battery change, all those problems seemed to clear up.

 

I concur. You wouldn;t have to hear them all the time for them to start going bad. Another common issue is the wrist pin on these engines. Try unplugging one plug wire at a time, to see if you can get this to stop briefly. If it does it all the time, then you know you have a valve issue. But if you can get the knock to stop (say when you pull the #4 plug wire off for example) then you know its bearings, or wrist pin.

 

Sounds a lot like a HG or valve issue with the 60 psi drop (that's a LOT). Are you certain it's not the head gasket???

 

It might be but I still get a knock and if it is the head gasket, it's only affected one cylinder and no radiator fluid is pouring in the cylinder. It doesn't smoke on startup or anytime anymore although it did at one point. I'm going to do the spark plug wire test and report back what I find.

I forgot to mention it's the 22RE in an 86' 4runner.

 

front main bearing has a little to much clearance. More pronounced when engine is warm (i.e. warm/thin oil)?

 

All to familier. Sounds like the old rod knock for sure.

 

I pulled the wires off all 4 cylinders and it still made the noise, a tad quieter when #4 was pulled. It only makes the noise under load and when opening and closing the throttle really quick. At idle, the engine purrs. I can hear it louder after the engine has time to sit but driving down the street makes it quiter, I'm guessing when the oil hits the valves, cam, etc. It gets quieter before the engine even has time to warm up. Considering a mechanic figured there was something wrong with my valves/head on the #4 cylinder, that's probably what it is but just want to get other opinions and see if anyone else has had this problem.

 

I just did the seafoam down the intake trick and noticed smoke was coming from the engine bay. Since I don't have an exhaust leak I was looking around and found seafoam coming out of where the head meets the block so I guess I do have a blown head gasket. Would this cause a knock sound? It's right at the back probably affecting the 3rd cylinder just a little bit but I guess it didn't blow near a water hole because the truck cools great and doesn't smoke.

 

I have exactly the same symptoms (though on a 3.4L) and to me, it sounds more like an exhaust leak, though it's "sharp" enough that I could see it being thought of as knocking.

On top of things, I'm throwing a misfire #2 code. For me, this all started when I pulled out to pass someone on the highway a couple of weeks ago. I jumped on it and heard "PFFFFFFFFFFFSSSSSSTTTT" and then "pfft-pfft-pfft-pfft" in time with the engine RPM. Exhaust color is normal, engine runs nice at WOT, but chugs and lugs below 1200rpm with some _nasty_ vibrations at 1500 or so. I've had to kick up the idle in order to stop it from stalling at the normal 600rpm idle.

 

in the owners manual it states while heavy accelerating, accelarting under a load, and accelerating up hill, you may notice a knock. it also says pay no mind as it is normal. in my own experience, i haul ass up hills, when i pull trailers, and ive run my truck at the drag strip for a good laugh....have i ever heard this knock? no.

 

Funny thing is, it runs pretty damn strong for having 33" tires, weighing 5k pounds and having a blown head gasket. It idles very well, accelerates very well (guess that can only get better now) engine doesn't shake excessively but I do have a misfire on slight acceleration. Guess I just got lucky. Well, off with the head, it will be nice to have a fresh gasket and probably a new cylinder head too.