Annoying Rattle 1996 FZJ80

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Need your help here guys..

cannot for the life of me figure out this rattle, only happens in gear between 1200-1500 rpms, sounds like pennies in a tin can. I’ve went through heat shields, U joints, and playing with timing and higher octane fuel but it’s still there. I’ll try to attach a video, it almost sounds like the sound is originating near the plenum area, any thoughts?
 
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Fueling issues (running lean, clogged injectors, leaking injectors ect....), excess carbon build-up in the cylinders. Also, your knock sensors should be adjusting timing to control it, so likely they are bad in addition to the listed concerns.

This is all IF it is actually knocking/pinging.
Can knock sensors go bad without throwing codes? It’s a 96. It runs like a top this has been the only concern so far. Last night I adjusted the timing to 6 degrees to test and sure enough the pinging rattle came back, brought back to 3 and quiet.
 
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Throwing any codes? What's your idle in neutral/park when fully warmed up? I wonder if you have a vacuum leak leaning out your mixture.

If not, I would probably spend some time on BobIsTheOilGuy.com looking for additives to clear carbon, and I'd find a nice, long hill. I've got a long, uphill freeway on-ramp locally that I take at full throttle every now and then just to help clear out carbon.
 
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Throwing any codes? What's your idle in neutral/park when fully warmed up? I wonder if you have a vacuum leak leaning out your mixture.

If not, I would probably spend some time on BobIsTheOilGuy.com looking for additives to clear carbon, and I'd find a nice, long hill. I've got a long, uphill freeway on-ramp locally that I take at full throttle every now and then just to help clear out carbon.
A vacuum leak would actually make it overfuel and run rich.

You're allowing in excess O2. The O2 sensors read the extra O2 and the ECU increases the fuel to prevent a lean condition.

OP: Pull your spark plugs to evaluate for condition.
 
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A vacuum leak would actually make it overfuel and run rich.

You're allowing in excess O2. The O2 sensors read the extra O2 and the ECU increases the fuel
I've read this before and I don't believe it. If the fuel mapping can correct that far, then it would simply adjust it to the point that the mixture is correct. Why would a leak make the ECU *overcompensate* and cause a rich condition?
 
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But if the O2 sensors aren’t reading well, then the MAF will be expecting less air and only inject a lower amount of fuel. So it is possible a vacuum leak could cause leanness IF the o2 sensors are faulty but not faulty enough to cause a code...
 
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Throwing any codes? What's your idle in neutral/park when fully warmed up? I wonder if you have a vacuum leak leaning out your mixture.

If not, I would probably spend some time on BobIsTheOilGuy.com looking for additives to clear carbon, and I'd find a nice, long hill. I've got a long, uphill freeway on-ramp locally that I take at full throttle every now and then just to help clear out carbon.
No codes, idle is about 600 fully warmed up. Idles great. I tried some gum out today so we will see
 

TYM4FUN

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I doubt fixes in a can will do anything. This will be hands on for you. Pulling injectors for service, refreshing head, hand cleaning/inspecting pistons, checking flow volume and pressure of the fuel system ect.... Something or somethings need to be fixed. Cans won't work. I tried, zero visual results on tear down or inspection of items. I did not have the issues you state, but know the results of "fix in a bottle" first hand.

Only thing you will notice in your situation, are some fluids will raise your octane. Thus reducing your current problem until the additive runs out.
 

Tedward

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I've read this before and I don't believe it. If the fuel mapping can correct that far, then it would simply adjust it to the point that the mixture is correct. Why would a leak make the ECU *overcompensate* and cause a rich condition?
A vacuum leak would actually make it overfuel and run rich.

You're allowing in excess O2. The O2 sensors read the extra O2 and the ECU increases the fuel to prevent a lean condition.

OP: Pull your spark plugs to evaluate for condition.
I had a vacuum leak past the mating surface of the intake plenum and cylinder head.
A large leak because I did not torque the hardware to fasten the plenum.
Drove like that for some time and miles before I finally found the problem/my mistake.
During that time the engine would run lean. Way lean at idle and a bit less under throttle as read by the ultra gauge.
The ECU compensated with more fuel the best it could, but not enough.
There is a limit to how much extra fuel can be delivered. My leak outmatched the extra fuel and then some.

The ECU will show a code when the extra fuel is added past a certain percentage over the base fuel map.
Don't quote me but I think it's 18 percent shows a code and 30 percent is the max percent that can be added. Those number are likely be off but are close.
Point here is unmetered (after the MAF) air (O2) was sucked in. The ECU adjusted with more fuel because of the O2 sensor readings in the exhaust.
It still ran lean.

Just junk food for thought.
 

Howard705

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Isn't the video of it in park just being throttled up?! I can't hear Pinging/detonation. Even if a noise was heard the only time i think Ive ever heard Actual pinging under no load in neutral was if an engine had ZERO coolant in it and run up to about 400f degrees or if someone wound a distributor around 50 degrees by hand playing with it. This appears to me to be just a bit of an internal rattle unless the video is not the actual problem. May be some loose parts inside or collapsed piston skirts etc.
 

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