High-mile 5.9- smoking on start up.

I've got a 99 2500 4x4 with a 360. It's got approximately 225,000 miles on it. I'm the third owner of the truck and it runs out pretty well. However, I've noticed it's got a nasty habit of smoking upon startup and initial acceleration. It's not really a noisy motor, but it has a little bit of spark-knock and some valve train noise. I put new plugs in it when I bought it, and I suspect the timing may be off due to a sloppy chain, but of course there is no adjustment.

So, I'm kind of wondering what to do with it. I don't want it to take a dump on me at an unfortunate time. I'm a mechanic by trade so I'm not afraid to work on it, I just want some input on suspected issues that might be simple to remedy before I go yanking the motor and dropping in a different one, since it does run pretty well. I'm putting approximately 2 quarts a month in it. I'm thinking it's a leaking plenum.

Hello and welcome, I see this is your first post. Being that you are a mechanic by trade I might not have much insight but here it goes....
I was always taught start simple:
What color is the smoke?
When was the last tune up?
How about cleaning the TB?
Rings/Gaskets/Fuel pump-Filter?

I am not a mechanic by trade but I fix Barbies heads when my little girls accidentally play to rough. Just kidding...some free humor. Best of luck and keep us updated.

I'll be honest, the old adage "the shoemaker's kids go shoeless" applies to me. I don't work on anything of my own unless I absolutely have to. I do like this truck though and I'd like to give it a fair shake. Like I said I put new plugs in it and the wires and cap/rotor were done within the last 10k. The smoke is blue and it stinks so it's definetely oil. I'm not losing a whole lot of oil under the truck onto the ground so what I'm replacing is definetely dropping down into the valves. The TB is pretty clean.

Then I think you might be on to something with your timing. I don't think it is the plenum leaking. 2 quarts a month sounds like piston rings.You sound like you've done a great job on your own diagnosing it. Stick around and others will chime in.

I'd bet cash money on a leaking plenum pan gasket. This explains the spark knock and oil consumption. The chain may have some slop and it may have some spark scatter but the timing itself is probably where it belongs unless the distributor was pulled and never put back in sync. You can check the cam/crank sync with a scan tool.

Ok, I'm hoping you are right, since that make me avoid pulling the motor. I'll have to climb up on it and start pulling apart to check.

Thanks Randy for jumping in....I will go clean the kitchen now.

Time for the the newer kit

Due to funds, I went ahead and installed the regular gasket. Trucks seems fine now, no smoke, more power, better MPGs. I know it will probably be temporary but it's all I had to work with. Thanks for the input.

willyjr said:

Due to funds, I went ahead and installed the regular gasket. Trucks seems fine now, no smoke, more power, better MPGs. I know it will probably be temporary but it's all I had to work with. Thanks for the input.

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If the plenum pan gasket is metal, you should be fine from here on out. the original paper gaskets were nothing but trouble.