I have a D6TXL with a C9.3 engine that is misfiring on number 4 cylinder at low idle below 1500 rpm. Above 1500 rpm it clears up. We have replaced the injector with a reman cat injector. Pressure checked the cylinder and changed the ecm but no change. Has anyone experienced this problem? Any advice would be appreciated.
Have you tried looking at Diagnostic Codes.? It may be possible to get at them using the Monitor. With a S/N I could find a procedure for it.
My mechanic has hooked up his computer to it and it does not tell him anything. It’s not telling him anything is wrong with the wiring.
He is using Cat ET diagnostic software I take it.? What’s the tractor Serial Number.? I wonder if something in the operating side of the injector could be the issue.?
GMK00665
Quick question. When was the last time the valve clearances were checked.?
Wonder if there could be an issue with the camshaft? Has the overhead been checked?
He hasn’t checked the overhead yet. But he put pressure on that cylinder with the valves closed and it held pressure. Just did not want to dig to deep into the engine if not necessary.
First thing that came into my head was camshaft/followers on that cylinder. Checking the clearances might just tell you something, especially if one of them is on the big side by a fair bit. The problem might not be related to the valves closing correctly but to them not opening far enough. Check for damaged/broken valve springs while you're at it.
That makes sense. I will tell him to check that tomorrow if he hasn’t already.
I would suggest that he does nothing more than measure the clearances as a first step, then report the results. Specs: Inlet 0.015 ± 0.003 inch, exhaust 0.025 ± 0.003 inch.