Engine knock - 2 different engines?

Ok I pulled my badly abused 4.0l Renix (read heat seized 3 times in one afternoon and held mostly to the floor while mudding by my buddy who was the previous owner) out of my '88 last week as it had developed what sounded like a wrist pin knock under light load over 2000 rpm. So I put in a fairly low mileage (180km 110mi) motor from an 89 which we ran around the yard and I revved up quite a bit before I pulled it from the old truck to make sure it "sounded ok" and incidently it makes tons more power than the old one which is good.
The bad is that the knock is still there, and actually it is worse. It knocks badly on startup and again as soon as it is over 2000rpm again which leads me to believe that I have a electronic problem and what sounds like wrist pin is actually detonation.
Ok all the sensors are from the '89 except I did break the knock sensor on the driver's side of the the engine and replaced it with the one from the original engine.
Does anybody have any input? Is the knock sensor possibly bad? I am going to swap the computer from a 91 I have or even the 89. Will the computers mess up timing on these Renix engines and where is the mass air flow sensor located?

Thanks
dj

:helpme:

Could it be an noisy injector? I say this b/c i might have the same problem, i think. ticks a bit at start up for a few seconds; ticks rhythmically fast at medium acceleration (going up hill at 2200rpms or so); ticks really machine gun fast in overdrive @ 3000rpms or so).

First i thought lifter, but I am really having my doubts, since i have seafoamed, mystery oiled, lucas stabilized . . .you name it and there is no change at all after 3+ years of doing it. Also, power seems great.

I also though manifold: I don't think so now. No visual cracks + passed the seafoam test.

Now, mine is a 98, so you might be on to something with the knock sensor. i really wouldn't know. but it does sound like its not the actual engine . . .that would be too big of a coincidence.

No this is definitely not an injector, it is not a tick it is a "oh boy I hope that is a diesel otherwise that sound is just not right"!

dj

Ok changed the CPS (crank position sensor) or as some people have called it on here the ping or knock sensor from another used motor I have and that seems to have fixed the problem......well I can hear a really weak knock still when I am revving it hard but it definitely does not sound like a diesel under light acceleration. I hope I didn't do any damage with all the detonation, or could it be that this used CPS is on it's way out?

dj

a small knock is typical of a 4.0L

Did you check your flex plate for cracks?

Could be a lot of things. An old school test is to pull the plug wires one at a time and see what happens with the knock. A diesel knock, too little fuel from a partially plugged injector, will probably go away. Wrist pin knocks, tend to also disappear, when the plug wire is pulled.
This method can be a shocking experience, keeping your crotch off the fender while doing it, is advised.
Piston slap and even which oil you use cab also be a factor.
You mentioned 2000 RPM's, In my experience this is where a lean running motor will first show signs of detonation from lack of fuel, often it's the O2 sensor or the wiring. The wiring from the O2 sensor runs up the front of the motor and it routed incorrectly (or even by itself on the earliest 4.0's 87 or so) will cook on the exhaust manifold.
Anything is possible, but in my experience the connecting rod bearings go out first and knock, piston slap is common, but usually worst near idle. I've had lean burn dieseling in most of my 4.0's at one time or another for various reasons. I've even had vacuum leaks cause it. I use a piece of pipe or a stethoscope to localize the knock as much as possible.
Let us know what you find out.