i just purchased a 98 1500 4x4, 5.9, bought it for $2,800. the problem is when u crank it, runs fine no problems. as soon as you rev up to about 1500 rpms it starts smoking dark grey smoke alot!!!! now this is a huge smoke cloud it puts out. but when back down to idle it fades out to no smoke again.... i was thinking a ring but it only smokes when you gas it, has plenty of power and runs smooth. is there someway it is getting oil into the intake and strait into the cylinders. ive unhooked the pcv from the intake, thought it was sucking oil in from valve cover. no luck. where else is it sucking oil in at???? its not the head gasket i know. any help will be appreciated..thanks

 

welcome to DF... I'd start by yanking the plugs and have a look. that will narrow it down to a cylinder or two, then go from there. you might also want to doa compression check, find out what kind of shape the cylinders are in (if they are building compression or not).

 

compression test first ^

then check plenum for oil inside intake manifold

remove air box and open throttle plate and look inside intake with flashlight for oil pooling up inside

 

My mustang did that and it was a hair line fracture in the aluminum intake.I think the smoke was light blue though. Compression test would be a great start.

 

im thinkin its a cracked intake. its got oil sitting on the bottom of the plenum. i unhooked my pcv while running, put my thumb over pcv hole on the valve cover, which sould now have no suction, and over the hole on the other valve cover and its got MAJOR suction, when u let off the hole it has alot of pshhhhhh, sucking. so would that make it a cracked plenum to suck oil in from underneath?

 

the plenum gasket is a known failure... just have not heard of the grey smoke associated with it before. maybe yours is so sever it's the 1st to my knowledge...

there is a DIY writeup in the DIY forum on how to do the plenum gasket if your up to it. not a hard task, just takes a while.

 

welcome to df. read the diy's on plenum gasket repair - its very very common. get the hughes kit with the aluminum plate that replaces the flimsy steel plate. plan it out... since you have to tear down the top of the motor, consider the age of your water pump, hoses, timing chain, thermostat, etc. if your mileage is below 200k, this will probably fix it back like new, or at least better than its been in many years.