454 tbi occasional oil smoke?

[shanegtr]

Just wanting to pick the brains of the guys who know their way around these engines more so than me. I have a 454 tbi in my burb and I get the occasional bit of oil smoke on start up and deceleration. My initial thoughts are valve stem seals but just thought I'd ask here in case there's something in the pollution gear that could case it also. The smoke does not occur at every start up and nor does it occur every time I lift off the accelerator. (My thinking if it was valve stems then it would do it all the time?)

 

[climb-101]

from what i have seen, if it’s the seals for the stems it’s just on startup after sitting. they leak oil when it sits and it burns off when you start, when it’s running the oil can’t build up so no smoke

 

[Mad gimp]

My dually does this if i let it sit for awhile..your start it and let it run for a few seconds and she'll let out a puff of smoke. Thats the only time it does it. I just say since theres a picture of indian Teepee on the corner of the cab, its sending indian smoke signals lol. Just kiddin

 

[shanegtr]

Hey all, just revisiting my earlier post to throw a little more info up. I'm still getting the smoke on start up, but at completely random times - there's more clean starts than smokey ones. As for smoke on decel it's most likely to do it after running for 10mins or so at highway speeds. I might get a light blue haze or a **** load, the longer I've been running at a constant speed the more likely it is for the later **** load of smoke. If for example I back off and she blows some smoke, I get back on it and return to the normal cruising speed and then within a few minutes I'm backing off again there would be a 99% chance of no smoke. My only thoughts are that it's still valve seals (but I would have though that would be a more constant/repeatable source of smoke rather than random), sticky oil rings, or maybe a built up of oil in the PVC system that gets sucked through every now and again. I did once have a SES light up at the same time as decel smoke (EGR fault code)

 

[Blue Ox]

How about the transmission modulator valve, if it has one? They're usually consistently leaky, but it may be something else to look at.

 

[Shorty81]

I've never seen an old 454 that didn't occasional puff a little smoke at start up. All the farm trucks thru the years did. If oil consumption is not bad I wouldn't worry about it.

 

[bucket]

I agree about valve stem seals, or a buildup of crud in the heads, not letting the oil return fast enough.

The smoking on decel, I'd point towards the pcv system or the trans modulator.

And it's funny, I've had a few 454's now and none of them have had even the slightest puff of smoke on startup. But my small blocks on the other hand, especially the original ones from the mid 80's, they have often fogged the area on a startup.

 

[shanegtr]

I'll have to do some searching on the trans modulator, if anyone has any links etc feel free to post them up

 

[1987 GMC Jimmy]

You should be able to pull vacuum on the modulator (rear, passenger side of transmission) and ensure that it holds without sucking fluid. If it doesn’t hold and sucks fluid or has transmission fluid dripping out of it, you’ll know it’s bad. Check your emissions diagram, it might be on there. I can’t remember, it’s been a little while since I had anything with a TH400. The PCV valve should rattle. If not, it’s bad. You could always test compression if your bottom line concern is blowby, but it sounds like valve stem seals worst case scenario.

 

[shanegtr]

Just another feedback post. I think you guys might be onto something with the Vac modulator. Had to top up the auto trans and no visible external leaks

 

[shanegtr]

Yep, vac modulator. Pulled the vac tube to be greated with auto trans oil. You can see it in the photo on the vacuum side.
Thanks for the help all, i wouldnt have even considered this line of thought if it wasnt for the forum help

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