Really, this is one of those cars that has me really thinking.

Here’s more things I thought of?
What does cracking the injector lines prove?

It has 6 new (just about) glow plugs, but even with that in 30 degrees, if it had low compression wouldn’t the motor be hard to start? It went over the first crank and fired up immediately.

It has 6 new fuel injectors. I also realized I worked on this car not too long ago (local car) and remember driving it when it had about 10000 less miles on it. It definitely did not used to have this rough idle and low power problem.

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Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k