The truck has about 250,000 miles. It usually takes two attempts to start and stay running, then the idle alternates between 500 rpms and 1000 rpms. It usually levels off at 500 rpms when warmed up. It sputters as it gains speed whether ita warmed up or not.

I have checked and cleaned the pcv valve, the egr, and mass air flow sensor. I.have also changed the fuel filter, the plugs and wires, cap and rotor, temperature sender by the thermostat, heater core, thermostat and air filter. Also, it appears the truck is losing water behind the water pump which I have not addressed beyond adding coolant every couple of days.

One thing I came upon while researching was the possibility that the fluctuating idle and sputtering could be due to timing chain slack(?). Otherwise, in efforts to address the issue, I just picked up a fuel injection pump tester to rule out the pump, regulator, and injectors.

Another issue is that the heat is not good and it's cold outside! I know it blows because I can hear it but to where I do not know. I suspect a door is stuck closed but I havent looked into it yet.

I want to address as much of these problems as I can this weekend. Am I on the right track? Are there any other issues that may be the culprit of these problems that I am missing? Thanks for any guidance!

 

Sounds like a vacuum leak to me, likely the intake manifold gaskets at 250k. Might have a bad actuator with the heat. Are both heater hoses feeling warm/hot?.

 

I know its been awhile but I have had ball joint, tie rod, and alignment issues I have been dealing with (and other unrelated issues). Oh yeah, AND I nailed a large whitetail buck going 55mph which took out the grill and driver side lights, dented my hood, and bent my number. So it's been busy busy...

The answer is "yes." Both hoses going to/from the heater core are warm. If I didnt mention already, I have a leak which appears to be coming from the water pump . The leak is to the point that I have to ad about a half a gallon of water after an hour driving.

 

Sorry to hear about the deer. To hell with the law, I'd have thrown it in the back, dressed it out and cooked it up. As to your water pump they don't come much easier to change on a Chevy small block.Pop the S-belt off, (might have to undue the shroud) disconnect the hoses, four bolts and its out. Clean surfaces, new gaskets new pump, install in reverse and you are done. F**d and D***e like using it for the timing chain cover with alloy to contend with but Chevy is all steel/iron, easy as pie to swap out..