Willdsl

Hello, I could use some advice. My engine has been slowly getting worse over the last 9-12 months.
1. RPMs have dropped according to my tach from 850 or so to 600, less with A/C and lights on, like 500 rpm's.
2. It takes more cranks to start. Used to start bam, right up not even one starter crank. Now 5 or more cranks unless I give it throttle, then chukes black smoke when it starts.
3. Loss of power, used to go pretty good especially once you hit 1700 rpm's. Now doggish until almost 1900 rpms then the power comes.
4. At 23-2500+ rpms lots of grey smoke especially in 3rd gear. Used to give black smoke when I punched it.

Fuel filter, oil &filter, air filter all changed religiously at correct intervals.
Had valves reset at around 124k.

Any advice will be thoroughly appreciated.

mysterync

Still have a fuel heater? What kind of fuel pressure are you making?
It could also be timing but its worth checking the basics first. From my experience timing usually isn't a gradual loss, it normally a fairly instant and notable change. Generally the only slipped timing I've been present when it happened is after a pump has been recently installed or timed and torque specs were not met or the mating surfaces were not cleaned correctly. I've timed trucks that had slipped without being touched but never been in one when it slipped in that type of situation.

Lil Dog

Sounds like air is getting in the lines. Have you replaced the fuel lines lately? Notorious failure point is the rubber lines between the engine and the frame. The Fuel heater is another leak point for air as already posted.

Second to that may be an overflow valve failing. This would lower fuel pressure and cause the same symptoms.

Tate

First two issues sound like low idle. Bump it up and those will be solved. Last two could be fuel pressure related, timing related, turbo related, AFC related. Check your FP, check out the health of the turbo, make sure there is no rips in the diaphragm in the AFC. Have the timing checked out if you can find someone to do it.

patdaly

You said fuel filter changed, did you also clean the pre-filter?