Engine/Transmission (1998.5 - 2002) slight miss at idle

[mongoose]

Just recently started: after truck is run and pull up to stop light or stop sign, truck seems to miss at idle. Not a particular pattern, might miss three times real quick and then not do it again for 10 seconds or so. Tach seems to flinch when the miss occurs.



New fuel filter did not help.



Could this possilby be a cam sensor or something similar?

 

[Todd T]

Well i just had a nice awakening on this or a similar problem. mine would run a little lumpy and give out a good shake on start up on a cold morning. i was also hearing some glug glug sounds through the open (K&N) filter element.



when I pulled the head to prep it for the twins I found one burned valve (#5 exhaust) and a second that looked pretty suspicious (#3 intake)



this truck had 135K never seen a trailer or a bomb so you cant rule this out even on a stock truck.



$1900 later it runs like a singer sewing machine

 

[mongoose]

oh, now i'm really scared. Going to do a valve adjustment on it monday and see if that helps.

 

[Todd T]

It may, i'm not saying that's your problem but on my otherwise hardly used truck that was my problem. the heads on these are not all that great of a design. the hardened seats they put in still develop cracks and you cant just re-grind them. they have to be taken out and replaced along with the guides. OK, you can re-grind them but not for any type of performance use, the cracks are still there just the seat is even again, for a while.



like i said, 135K on a truck that has NEVER seen a trailer and maybe the worst action it ever saw was long idling times in the Texas traffic/heat. it's head was disturbingly damaged for that amount of use.

 

[DNolan]

Do you have eletric sending unit? Mine went south twice. just a thought!! Caused a Miss like yours. Scott@ Massdiesel and I went nuts trying to find the problem.

 

[mongoose]

Did a valve adjust over the weekend. seemed to help. I had a couple of intake valves at . 014 and a couple of exhaust at . 022-. 023. Pulled the intakes down to . 010 and the exhaust to . 020.



Truck seemed to idle smoother and i did not notice this miss this morning.