Irratic at 3,000 rpm

[Bzybuoy]

After replacing the harmonic balancer due to rough idle and noise coming from it and replacing the crankshaft sensor at the same time being that I was down there anyway My truck started throwing a combination of codes, —— PO300, 301 and 305 which is a general random misfire and misfire on cylinder one. misfire on cylinder five. This was not happening before I replace the harmonic balancer so I went ahead and did the easiest thing being the truck is still somewhat new to me and it has 140,000 miles and change on it (I didn’t mention that it is retired DPW Supervisor’s fleet vehicle from Suffolk County, thus making the 140,950 irrelevant imho by means of that it has idling hours most likely closer to a vehicle with 400,000 on the clock and never went over 40mph in its life) )and I replaced the plugs wires and coil being the easiest thing to start with it really needed that! The plugs were showing signs of a lean condition or overuse of a fuel system cleaner. That solved the codes for about a half of a day until I went to go home from work and it’s threw the codes again. Which prompted me too start replacing the most likely near end of life sensors. MAF, EGR control solenoid, and the crank sensor. Also fuel filter after doing a pressure reading off the rail and getting 45lbs and then even lower after doing the plugs and wires/coil. Now that. Made me do the fuel pump I dropped the tank down and did that. I removed the intake manifold and thouroghly scrubbed out carbon deposits like I’ve never seen before. Pulled rail and all injectors, screw that getting them clean shit on this case I bought all new ones $$$$ . Underneath a few of them were injector adapted seals that were fractured and cracked so I replaced all of them too. Inside the two misfiring cylinders and another injector port it looked as if it was plugged solid with carbon deposits. Cleaned that the best I could and then polished the ports on the rail and head where the injectors seal with a dremel and a “scotch” pad rotary bit. The Intake o-ring seals that are known to allow vacuum leaks i cleaned and coated with some high temp red RTV silicone gasket maker and polished the surface on the heads where they mate up to. I replaced the pcv valve and put a new EGR gasket. I vacuum tested the egr valve and it is working and the entire vacuum system is holding a 21lbs vacuum. Idle is normal now no roughness and throttle is responsive but when I bring it to 3,000 rpm at a standstill it tops out and it starts jumpIng up and down like it has a governor or it is starving for fuel. I am putting tools away and I will take for road test in a little bit to see what it does under load but any advice would be greatly appreciated thanks in advance

 

[DILLARD000]

There is a limiter at 3000rpm when idling in Park\Neutral;
don't recall what year that was first used.

 

[Bzybuoy]

There is a limiter at 3000rpm when idling in Park\Neutral;
don't recall what year that was first used.

Well that would explain why it seems like a limiter! And I took it on my commute today about two hours ago and it ran perfectly through the gears and no hesitation at 3,000 or misfire codes generated. I’m gonna do some research on rev limiter and see if I come up with anything interesting, thanks dillardooo