1997 FZJ80 rough/trembling idle

[Rain]

hi everyone, i just bought a 1997 LC80, my problem is my engine trembles at idle, idle is 600rpm and it would go down to 400 sometimes lower like stalling, but at higher rpm above 1000 the tremble disappears and the engine is solid and responsive, i have checked all the plugs, the air intake hoses,air filter,the FPR, the engine harness( mine doesn't have the EGR= Dubai ver), the iac, the TPS, latest done was compression check on all 6 cyl which give constant 220 psi, Hope you guys can give some more ideas what's wrong with my 80.

Regards and more power to all.

 

[94SRUNNER]

Have you checked all of the vacuum lines?

 

[Sanchez]

How about fuel filter and fuel injectors?

 

[phatairman]

I had this same issue and my problem was the porcelain was cracked on a spark plug.

 

[firetruck41]

Replace your plug wires if they are original.

 

[4x4CPOSEADOG]

hi everyone, i just bought a 1997 LC80, my problem is my engine trembles at idle, idle is 600rpm and it would go down to 400 sometimes lower like stalling, but at higher rpm above 1000 the tremble disappears and the engine is solid and responsive, i have checked all the plugs, the air intake hoses,air filter,the FPR, the engine harness( mine doesn't have the EGR= Dubai ver), the iac, the TPS, latest done was compression check on all 6 cyl which give constant 220 psi, Hope you guys can give some more ideas what's wrong with my 80.

Regards and more power to all.

Firstly, welcome How many miles do you have on your 80 when you bought it? Where are you located?

 

[Rain]

Hi guys and thanks for all your ideas, i have checked all the vacuum lines even the small ones hidden under the intake manifold, the spark plugs were all good but i can try to buy a new set, i havent checked the fuel filter and the injectors yet, what my mechanic noted is that the engine is very solid at RPM above idle say 1000rpm, and you can feel a good launch from full stop, when cruising steadly its very smooth, he is now leaning towards an air leak possibly at the air intake manifold, I'am from Manila

 

[chitown40]

Check your intake hose for cracks, especially at the accordian section. Remove it gently and inspect while it is off the vehicle. It may be difficult to find some of the smaller cracks.

 

[REELhybrid]

TB

hi everyone, i just bought a 1997 LC80, my problem is my engine trembles at idle, idle is 600rpm and it would go down to 400 sometimes lower like stalling, but at higher rpm above 1000 the tremble disappears and the engine is solid and responsive, i have checked all the plugs, the air intake hoses,air filter,the FPR, the engine harness( mine doesn't have the EGR= Dubai ver), the iac, the TPS, latest done was compression check on all 6 cyl which give constant 220 psi, Hope you guys can give some more ideas what's wrong with my 80.

Regards and more power to all.

Had the very same symptoms....being that you just checked all the above, try cleaning the throttle body with carb cleaner.

 

[VanGo]

Follow the FSM to trouble shoot the resulting cause of the problem. I discovered 3 of the 4 wires terminated at the molex connector above the distributor had cracked housing, once I resolved the problem with heat shrinking each wire- no more hard starts, hesitations or rough idling.

 

[LC80Ducati996]

I had a small stumble. I cleaned the TB, checked and fixed any vac hose, etc... I ran some amsoil fuel system cleaner in the tank.. It helped. I have heard good things about redline.. It solved it for a while.

Then a low rpm miss happened again intermitently after I flushed the cooling system. I checked the spark plugs and the #6 plug showed signs of a tiny amount of coolant on it. So it could be a simple vac hose or a PITA head gasket.

 

[BillyGoatMTB]

Bump
Morning MUD

I have a slight stubble at idle. As a preventative item I want to track it down.

I saw in a previous post someone suggested looking in the molex box I can't find that in my FSM. Where is this located any pictures maybe it's as simple as some wires are cracked?

I have had this 1997 FZJ80 for 1 year. The maintenance and restorations I have performed are below.

Complete cooling system restoration including every hose and everything with the cooling new, complete tune-up plugs wires cap rotor dizzy o-rings, complete Dobinson 3" suspension with Delta radius arm and components, 35" BFG AT, fuel injectors have been sent in cleaned and balanced, fuel filter, no oil and intake since I replaced the spark plug tube o-rings and had everything parts washed, every vacuum hose is new and all vacuum switching components were tested with the factory service manual specifications and passed, every hose in the engine bay is new.

I thought about ordering Joey's intake MAF upgrade in hopes that would clean up the tiny stumble at idle but want to rule anything else out.

Thanks

 

[WarDamnEagle]

Follow the FSM to trouble shoot the resulting cause of the problem. I discovered 3 of the 4 wires terminated at the molex connector above the distributor had cracked housing, once I resolved the problem with heat shrinking each wire- no more hard starts, hesitations or rough idling.

Bump
Morning MUD

I have a slight stubble at idle. As a preventative item I want to track it down.

I saw in a previous post someone suggested looking in the molex box I can't find that in my FSM. Where is this located any pictures maybe it's as simple as some wires are cracked?

The typical wire connector (male side and female side) in your 80 are known as molex connectors. There's no molex box. The post you referred to references a connector above the distributor. I would just check all the connectors I could find. They are not hard to take apart. Just need a small screwdriver to depress a small latch on one side.

Welcome and good luck with the problem.