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spankyjr1, Journeyman
Category: Medium and Heavy Trucks
Satisfied Customers: 2602
Experience:  I worked on all types of equipment semis,forklifts,farm,ect.
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I have a 2000 c7500 with a vortex 7400 454 RPO code L21It

Customer Question

I have a 2000 c7500 with a vortex 7400 454 RPO code L21
It has what appears to be at least one dead cylinder depending on the engine temp.
I have replaced all coil packs, plugs, wires and injectors. My snap on versus can't pull any pending or active codes no check engine light or anything. Basically it starts up idles fine runs OK if you take it out on the road until it warms up and then it loses a cylinder maybe more. It has no power and you can hear the dead cylinder going g down the road. Until I replaced the injectors it would shoot an exhaust flame once this started. There's a bit of oil on the back 2 plugs on the drivers side leaving me to believe it needs valve seals. Any help would be greatly appreciated!
Submitted: 2 years ago.
Category: Medium and Heavy Trucks
Expert:  spankyjr1 replied 2 years ago.
Hi, my name is ***** ***** you for your question.
Get engine hot when miss is present,,use a laser temp gun to find which cylinder is miss firing,,then do a compression test and leak down test of suspect cylinder to confirm problem.
Just point laser directly at exhaust port on head above manifold and compare readings to find one or more cylinder miss fire.
Laser temp gun prices vary so shop around if you don't have one, I have seen them lower than $30.
Just in case test is good swap a injector with bad/good cylinder since I have got bad ones out of the box.
I agree oil is probably valve seals but that won't cause a miss unless plug is fouled.
The flame concerns me,, may be a bad cam but testing exhaust temps and compression test will confirm
Questions or problems let me know I'm happy to assist.
Expert:  spankyjr1 replied 2 years ago.
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