2012 L4600 Loping at Idle

curtmlee

New member

Equipment
L4600w/loader M108S
May 19, 2026
1
0
1
South Dakota
I have a L4600 with 750 hrs on it. It started to white smoke at cold start, a slight ping when cold and when warmed up it lopes at idle. I removed all the injectors and the injection shop said the pop pressure was low on all of them. They replace the tips cleaned them up and I reinstalled them. White smoke at start up is gone, slight ping when cold is gone but still have loping at idle when warm. If i crack the fuel injector lines while loping, the #1 cylinder doesn't seem to slow the engine down. if I rev the engine up to over 1100 rpms the engine smooths out and cracking the #1 fuel line slows the engine down. Using a AI chat sight they say I have carbon build up in my prechamber of #1 and running is under high speed and power will clean this up. Has anyone else had this issue?
 

North Idaho Wolfman

Moderator
Staff member
Lifetime Member

Equipment
L3450DT-GST, Woods FEL, B7100 HSD, FEL, 60" SB, 743 Bobcat with V2203, and more
Jun 9, 2013
35,723
10,793
113
Sandpoint, ID
AI is pulling your leg!
Really confused by your " They replace the tips cleaned them up " that won't effect the pop pressure.
Weak springs and shim count effect pop pressure.

Sounds like you have either a bad injector, valves out of adjustment, or a bad injection pump, or possibly cylinder damage.

(Long shot advice) Run some Stanadyne or other fuel system cleaner / fuel system conditioner in the fuel and see if that help clean it out.

Pull that injector and swap it for another and see if the issue follows the injector or stays put.
If it stays put, do a compression test on all cylinders.
 

North Idaho Wolfman

Moderator
Staff member
Lifetime Member

Equipment
L3450DT-GST, Woods FEL, B7100 HSD, FEL, 60" SB, 743 Bobcat with V2203, and more
Jun 9, 2013
35,723
10,793
113
Sandpoint, ID
They reset the pop pressure. The valve lash was checked. The engine runs good cold, high rpms and under load. Just hot idle it lopes. No smoke or oil consumption
Why do we have 2 different accounts commenting on the same issue?

Move the injector and see if the issue moves.