1998 dodge ram 2500 5.9l gas.. cylinder 8 misfire, runs very rough, newish cap and rotors, shudders and hesitates when accelerating, absolutely doesn't like hills, terrible fuel economy... I keep wanting to think it's the plenium gasket or whatever but I'm not loosing any oil? About 2000 miles since last oil change and it's still full.. do you think it's the plenium, truck has 172k miles

 

Need to have a look down in there, see what you see. I expect to see SOME oil in there, just from the PCV system. That should be a spray like pattern, if oil is pooling, that's an entirely different kettle o' fish.

What plugs in there? How old are your O2 sensors? Getting any codes? Flashing check engine lite?? How are the plug wires? Probably wouldn't hurt to check fuel pressure as well...

 

I'm not sure which plugs are in there but they were changed with cap and rotor about a year ago, 02 sensors, probably not good honestly, I've only had the truck for about a year so, cel is on not flashing the code was for a cylinder 8 misfire

 

Would that work for fuel pressure tester?

 

Looks like it should. If you dont really need to have one permanently in your toolbox though, you can rent them from the big chain auto parts stores. You get your money back when you return it.

 

NO! Not for your vehicle.
This is for carbureted vehicles NOT efi. You need one that will go past 50 psi like this one.
https://www.harborfreight.com/fuel-i...ter-58760.html
As for the plenum I look at it like this, You have a known problem area. Either fix it now or fix it later.

 

Ooops. Missed that. Thank You.