Got a 1996 F350 with the 351w 5.8. Truck starting puffing blue smoke from the exhaust but only at idle and after it had been warmed up. Does not smoke on start-up or while driving. Thinking it is the rings I did a compression test to make sure. But now I'm stumped.

The compression test was on a cold motor. Here are the results,

Passenger side
1-135
2-130
3-135
4-135

Drivers side
5-150
6-150
7-150
8-150

I have no clue why one side would be so different from the other. Any thoughts PLEASE!!!??? I didn't do a wet test yet. Just don't think all the rings are bad on only half the engine.

I have pulled codes and have a 334 code on both KOEO and KOER tests. It has to be a short because everything is new (egr, sensors, vacuum lines, etc.)

 

I would check the pcv valve. Do you have a lot of blowby in the air cleaner? That would be a sign of bad rings but i agree, rings usually dont go bad on just a side.

 

The pvc is new. But...the pcv groment was never on correctly for a long time. I didn't find this out until I took the upper intake off. Any chance that could have caused a problem?

 

The air cleaner is pretty clean. There is a little oil on the sponge from being there so long but that is to be expected.

 

Is there a lot of build up in the runners of the intake? If its a pcv valve the #8 cyl runner will be coated with oil.Usually if the rings are bad,it will smoke all the time. I would also pull the valve covers and make sure the oil return holes are not plugged with sludge.

 

Not sure what exactly the intake runners are but if it means the air flow passageway ways between the upper (plennum) and lower intake then yes they all had some build up but I don't think it was much. Carb cleaner cut through it and none were much more excessive then the next.

The truck definitely doesn't smoke all the time. I run a small trash route with this truck so I am in and out of it all the time. It only starts to smoke shortly after idling and after it's up to normal temp. I can't see any smoke when I'm driving unless it too minimal to see.

I'm wondering if fresh air within the valve covers wore out the seals. The pvc valve on that side had been super loose for at least the 15,000 miles I've had the truck for.