My truck has had a sort of miss at idle for some time. It's not so much noticable from the engine as it is at the exhaust. Kind of a puh puh puh noise but its not always there sometimes Ill stop at a light and its there then smooth at the next. Dealer said it was my valve guides and would cost $2500 to repair but I dont put to much faith towards that.
Anyway I have replaced liftpump (10 psi at idle) fuel filter many times. Could this be an injector or injection pump or maybe computer trouble?
any suggestions greatly appreciated.

 

Next time it is missing, feel each of the injector fuel lines. If one feels different, that is probably the injector that is bad. I would think sticky injector, maybe dirty nozzle.

 

This happened to me, it was missing at idle. I took it to a shop in Salt Lake City, he tested the compression and found it to be OK, he tested the injector and that was OK. He then pulled the injector pump and had an injector pump place test it, they found two delivery valves that needed new seals.

I was able to narrow down what injector line was bad by feeling the exhaust ports on all 6 cylinders, when they were cold, and finding the one that was not heating up the same as the rest.

It runs sweet now. ;D ;D

Cost me $700 :'(

 

Thanks yall Ill give it a shot. Other than the front end giving me fits, this is the only trouble I have had with the truck and she's pushing 175000 miles.
Guess I shouldnt complain to much.
Thanks again

 

Overflow valve took care of my "miss" at idle and just above it. This is the cheapest thing to start with. If not changed in awhile, do it. For best price, do a search, plenty of info. Kevin

 

kkwhite4

When my '91.5 did the same thing and sounded the same at the exhaust it was the injection pump at 140,000 miles. If you have not replaced the pump yet, it is likely the problem. Mine did not miss at speed, only at idle. Unfortunately, injection pumps are expensive.

 

Note the truck in question is a "98.5" which puts it in the 24v vp-44 gang. Noted alot of "dumb pump" suggestions here which wouldn't apply. Congrats on having a VP last that long, especially on a 98.5. Look at the bright side if it's the pump. When the 98.5's came out that pump sold for over $2500 new. At least now you can find re-mans for around $1000.

 

I have experienced that on a couple of early 24 valves. If the truck idled a lot, the valves would get sticky and bend a pushrod.
The miss wasn't intermittent in those cases, though. It was easy to find with the valve cover off and a feeler gauge.
Just a thought.

 

Where is the best place to look for an injection pump?
Wouldnt mind paying a little more if I know the quality is where it should be.So far I found one for 1200.00 + core at Oregon fuel injection but havent read anything about them.

 

My truck had the same phenomenon, and developed more smoke than usual- had to change my injectors and it went away. ( DonMs Mach3s)
Do you run a fuel additive?

AlpineRAM