Injector #4 mechanical malfunction

what engine ?

 

Head problem possibly turbo for sure burned valve or bad cam one or the other wither or very expensive fix

 

I will bet on bad camshaft lobe.

 

Sometimes you are able to see it clearly in plain sight. If he could not, then he will have to remove rocker shaft (VERY HEAVY), inspect rocker arms and rotate engine while inspecting camshaft.

 

Every engine can be checked for cam lift without disassembly. If you have an issue where cylinder is not producing power and you suspect a valvetrain issue, valve lift can be measured with a dial indicator to match a known good cylinder or engine manufacturer specs.

This is a way to check cam integrity without teardown. This in no way inspects the parts for reuse or surface integrity and obviously teardown would be needed to see or feel surface imperfections. But if the lobe is flat or worn, bad follower, you'll know by only removing the valve cover and measuring. Overhead cam failures are usually pretty easy to spot without disassembly.

 

How many miles? Do you idle alot?

 

Remove injector #4 and do a compression test and see what happens