Could easily be a head gasket. Best pinpoint would be a leakdown test - feeding compressed air to the cylinders while on their compression stroke. Dennis

 

There is a fairly big difference between engine knocking and valves rattling, but a leakdown test beginning with #1 and #2 certainly wouldn't hurt at this point.

Have you tried pinpointing the source of the noise using a stethoscope or holding a long screwdriver between your ear and the engine block at each cylinder ?

Does the noise change if you rev the engine when it's parked in neutral vs driving around ?

Have you checked the timing lately ?

Do you see any evidence of water in the oil or oil in the radiator ?

Oh, and yes, it's a LOT easier to turn the engine over by hand with the plugs out !

 

I have not heard a blown head gasket make this sort of noise before. More of a knock than a rattling. Most evident when driving, under acceleration starting around 2k RPMS. Reving the engine while in neutral does not produce the same noise.

With stethoscope to the engine block it is the loudest near cylinder #2, more toward the top of the engine. Honestly hard to pinpoint as it is most noticeable when driving...

Timing has been checked recently. Haven't drained oil to check for contamination yet.

Hoping to get some more diagnosis time here in the next couple days. The tech at the shop its currently convinced the sound is coming from the top end. Probably going to pull the valve cover back off so they can take a look. Possible push rod or lifter problem he says? Top end looked good to me.

 

There aren't lifters or pushrods in the 4ZE1 since it' has an overhead cam. Under hard acceleration or light acceleration? It could be a number of things. Piston slap, bad piston pin, rod bearings, etc. I had a vehicle that I thought for sure had a knock in the engine. It turned out to be the inspection cover on the auto transmission was slightly bent and the torque converter bolts would touch it only under load. But since you have a 5 speed, that's a moot point.

 

It could be a bad timing belt tensioner. In which case it may have affected timing resulting in lower compression in #1&#2. Pull off the top half of the timing cover and see if your noise gets louder. I've heard tales that a bad tensioner can mimic a rod knock.

 

Blown head gasket can indeed sound like a knock on these engines. Especially if accompanied but a rattle sound.

A couple of years ago I blew a head gasket while climbing a hill near home towing my boat. I thought I had broken a rocker arm. That what it sounded like.

 

Update.

The local shop I took the Trooper too was unable to diagnose the problem. And it became evident pretty quickly they had no idea what the f*ck they were doing. (Suggesting lifters as a problem, beating on the starter with a hammer and ultimately being stumped and telling me the engine needs to be replaced without being able to point to a single definite problem.) Long story short, don't go to Bernie's Automotive in Seattle.

A local Isuzu friend pointed me toward the distributor in my search for what is causing the noise. Distributor cap was indeed damaged, fitting loose and full of moisture/oil/gunk. Cleaned it up, replaced cap and rotor. Reassembled, started trooper and... The engine kept cranking after turning the key. Starter just kept trying to start, even with the key turned off and removed. I actually had to disconnect the battery to get it to stop!

I am not sure if the issues could be related (The noise, Distributor, and Starter), but problems seem to be compounding. And obviously I can't get much further along in diagnosing the noise without the starter working properly. Also should mention the compression results from the shop are not to be trusted as I really doubt they did the test correctly (They were that incompetent). Thoughts? Could the starter being stuck on have something to do with the original problem/noise? or is it just a symptom of something greater going on? Hard to do much more until I am able to test/address starter.

Frustrated.

 

Starter should be completely unrelated. Starter is most easily removed through right fender well (pull the rubber out of the way or off - may need new fasteners if you do)
Double check that you have your wires back on in the right order.
Here's a new thought on your original noise problem: pull the cover off your exhaust manifold and check it for being cracked (check last page of my build thread). A cracked manifold can make ticking or knocking noises).
Sounds like you took it to the "Fred Flintstone Garage". Dennis

 

If your starter is not disengaging, check the mounting bolts are tight and the starter is on tight.....no telling what those bozos' did by pounding on it.

Check your spark plug firing order. you may have hooked your wires back up wrong if it is not starting.

 

No news on this? Another (real bad) possibility of a knock would be crank thrust bearings (hope not for your sake). Get a decent size screwdriver (or small pry bar) and carefully try prying the crankshaft forward at the harmonic balancer - carefully - it shouldn't take much force. Now try prying backwards (maybe at flywheel end if accessible) If it moves with any distance (1/8-1/4"), your thrust washers are shot (probably laying in the bottom of the oil pan). If this is the case, your engine block is probably history (unless you barely ran it after the knock). Hopefully, not your problem. Dennis

 

No news on this? Another (real bad) possibility of a knock would be crank thrust bearings (hope not for your sake). Get a decent size screwdriver (or small pry bar) and carefully try prying the crankshaft forward at the harmonic balancer - carefully - it shouldn't take much force. Now try prying backwards (maybe at flywheel end if accessible) If it moves with any distance (1/8-1/4"), your thrust washers are shot (probably laying in the bottom of the oil pan). If this is the case, your engine block is probably history (unless you barely ran it after the knock). Hopefully, not your problem. Dennis

 

Per Dennis & Jerry's recommendation, I checked for movement at the harmonic balancer. There is no movement that I can detect. I removed the skid plate and small metal shield to get good access to the harmonic balancer. Also, double checked and plug wires are connected correctly at plugs and distributor.

I guess this is good news, but I still am unable to diagnose the problem. At this point if the battery is connected the starter is cranking non-stop.

No news on this? Another (real bad) possibility of a knock would be crank thrust bearings (hope not for your sake). Get a decent size screwdriver (or small pry bar) and carefully try prying the crankshaft forward at the harmonic balancer - carefully - it shouldn't take much force. Now try prying backwards (maybe at flywheel end if accessible) If it moves with any distance (1/8-1/4"), your thrust washers are shot (probably laying in the bottom of the oil pan). If this is the case, your engine block is probably history (unless you barely ran it after the knock). Hopefully, not your problem. Dennis

 

Sounds like you have a problem in the ignition switch. You can remove the switch module without having to remove the entire switch from the steering column. inside the plasic module itself are brass contacts and springs. clean these up, and reassemble using a little white lithium dielectric grease, then reinstall. More than likely this will solve the sticky starter problem.

 

Non-stop cranking problem is with the starter itself. Unrelated to ignition switch. Wish it was that simple! I tried pulling the starter relay when it first happened and the starter keeps going.

Sounds like you have a problem in the ignition switch. You can remove the switch module without having to remove the entire switch from the steering column. inside the plasic module itself are brass contacts and springs. clean these up, and reassemble using a little white lithium dielectric grease, then reinstall. More than likely this will solve the sticky starter problem.

 

Then you have a bad starter....or it is hooked up wrong.

 

Pulled the starter. Jacked up the front end and went through the wheel well. Didn't even have to take the wheel off. Thankfully it was easier and quicker than I had anticipated. You can see the hole where the starter used to be in this photo.

Once the starter was out of the truck I could see that it was stuck in the forward or engaged position (failed to take a picture of this). I was able to get it to release by hand and go back into its normal position. It now seems to move freely, but I plan on replacing it with a whole new or reman starter.

Maybe I'll get lucky here and the sound could have been the bad starter. Perhaps partially engaged, knocking on the flywheel? Fingers crossed.

Any recommendations on where to get a quality starter at the best price? Thank you all for your help.

 

Try O'Rielly's auto parts their remanned starters are decent...take your old one with you for the core charge.

 

In the 3rd pic, are those hammer marks from where the tech "whacked" it? If so, no way would I let them work on my vehicle. May have something to do with the starter hanging? Sure couldn't have done it any good.

Mike

 

In the 3rd pic, are those hammer marks from where the tech "whacked" it? If so, no way would I let them work on my vehicle. May have something to do with the starter hanging? Sure couldn't have done it any good.

Mike

Yeah that is what those marks are from, it looks like they really beat on it...

 

Holy crap ! They really did a number on that thing.
Did they charge you for the bonus 'adjustment' ?
Any update as to whether or not replacing the starter solved the problem ?

 

I can see how many teeth the starter has. How many teeth did the mechanics have? Dennis

 

Question is, how many teeth does the flywheel have left? Lot of metal shavings on the business end of that starter.

 

Picked up a reman starter from O'Reilly's and popped it in the week before last. The guy at the counter said it looked like the unit had been on the shelf for at least ten years.

Freewheel teeth looked okay as far as I could see. Trooper starts right up. No more starter stuck on problem.

Idle is low after initial warm up cycle, but engine stays running. Took it for a spin around the block and the noise is still there. Next step checking/setting timing...

 

Actually , I think the next step is to change your oil and check for metal shavings in the bottom of the drain pan. It's a pretty tell tale way to see if you've got a bearing gone bad.

 

Actually , I think the next step is to change your oil and check for metal shavings in the bottom of the drain pan. It's a pretty tell tale way to see if you've got a bearing gone bad.

Drained oil and there was absolutely no signs of metal shavings. I ran a magnet through the bottom of the drain pan a couple of times and didn't find anything.