Need some guesses on what this could be. It started before I replaced the head and I thought the new head would fix it, but it was not to be.
Sometimes it idles perfectly smooth, and sometimes it idles (and off idle also) with something less than a miss.
I don't know what would come and go like that, but has to be the pump or an injector.
Thoughts?

 

My truck started doing the same thing about a month ago. Its not a full miss but not quite a lope. I installed a new set of Bosch oem size injectors and it made it worse. I think its in the injection pump getting tired. Does it get worse the longer you run the truck? Like when the fuel gets nice and warm?

 

I'm thinking pump also.

 

Is there any way to tell, say with a motor stethoscope, which injector isn't firing. Then swap the delivery valve involved with a known good one, or another on the truck. If you move the bug, you've found the problem.

It's a distributor pump. About the only parts in it after the distributor are the delivery valves.

If someone replaced a fuel line with a home made one, that be trouble too.

 

I could use my digital temp gun to maybe see a temp difference on the exhaust ports.

 

I have 3 cylinders reading reading 200-215 and the other 3 reading 150-160. I"ll have to look at the deliver valves. Isn't there cam springs or something in the pump that can break but still continue to run?