Just bought the truck has been sittn for three years.The cel light came on about a week after having it back on the road..started running rough.. it came back with cyl 5 misfire code..when i use 4wd most of the time the cel goes off and no misfire and runs clean..i checked vac lines from transfercase and they look fine but hard to tell..one of the 4 lines is disconnected up by the firewall but cant seem to find where it goes..any help would be much apreciated.. thanks

 

Is the plenum blown? How's the ignition parts look?

That fourth line is a vent line. If your 4x4 works, its all good.

 

im gonna do cap and wires this weekend just to rule that out .is there a way to tell if the plenum is blown? take off throttle body? and yes 4wd works fine other than some binding in the linkage when shifting in and out.

 

Check fluid in the T-case, might be a contributor to your binding.

Yep, pull the TB, and have a look around, if you see oil pooling in there, (corners especially...) plenum is blown. Fairly standard for these trucks anyway..... not an especially good design.

 

Thanks bud. I'll get back to you when I tear it down..

 

Forgot to ask can a blown plenum contribute to low compression on that misfiring cylinder?

 

In an offhand sort of fashion.... If left long enough, the products of burning oil foul the valve seats, and you start losing compression. Seafoam will help clear that up.

 

Seafoam? Sorry never heard of it. Can I get that the local parts store?

 

Yep. Or Wal-Mart, Meijers, and a host of other places as well I would think.

 

Ahh. Spray foam. Took a second there. haha Thanks again