Blue / White smoke at startup

[JIMMY92w]

Every time I start my truck if it’s been sitting for over 15 minutes I get a bluish, whitish cloud of smoke out of my tail pipe. It has a strong oil smell and can see it for up to 20 feet until it dissipates. I had taken the EGR off for a little cleaning / lubing and decided to fire her up to blow out any carbon crumbs. This time the blue smoke blew out of the EGR opening. When I inspect the PCV valve it seems oil laden! I just replaced the PCV. I am burning oil about a 1/8 to ¼ inch below the full mark every month. I change the oil every month with synthetic and its very clean. I changed my plugs from NGK platinum to standard AC Delco plugs. The plug tips looked perfect, but now with the non platinum I notice a major decrease in response and power, but better fuel economy. There are no external oil leaks.

It’s a 1992 GMC Jimmy. 4.3 CPI, 73,000 miles VIN W

I suspect the valve guide seals need replacing, but I want a second* opinion. I was reading one post from:

RLITH “As to the puff of white smoke, this is normal as well. On our trucks, a little oil will go down the valve guides and burn off when started. Even if you replace the valve guides, it will be back in 6 mos.”

Unfortunately my cloud is a little bigger then a little puff

Also are the Valve guides the Valve guide seals? I’m a little confused in what needs replacement.

Thanks for any input.

[Rick Norwood]

Originally Posted by JIMMY92w

Every time I start my truck if it’s been sitting for over 15 minutes I get a bluish, whitish cloud of smoke out of my tail pipe. It has a strong oil smell and can see it for up to 20 feet until it dissipates. I had taken the EGR off for a little cleaning / lubing and decided to fire her up to blow out any carbon crumbs. This time the blue smoke blew out of the EGR opening. When I inspect the PCV valve it seems oil laden! I just replaced the PCV. I am burning oil about a 1/8 to ¼ inch below the full mark every month. I change the oil every month with synthetic and its very clean. I changed my plugs from NGK platinum to standard AC Delco plugs. The plug tips looked perfect, but now with the non platinum I notice a major decrease in response and power, but better fuel economy. There are no external oil leaks.

It’s a 1992 GMC Jimmy. 4.3 CPI, 73,000 miles VIN W

I suspect the valve guide seals need replacing, but I want a second* opinion. I was reading one post from:

RLITH “As to the puff of white smoke, this is normal as well. On our trucks, a little oil will go down the valve guides and burn off when started. Even if you replace the valve guides, it will be back in 6 mos.”

Unfortunately my cloud is a little bigger then a little puff

Also are the Valve guides the Valve guide seals? I’m a little confused in what needs replacement.

Thanks for any input.

You got a 92 with only 73,000 miles? WOW, My 2000 Jimmy has got more miles on it than that. It doesn't sound like it gets driven a whole lot. You sure it isn't 173,000 miles?

First, if you're changing oil every month and using synthetic oil, Brother you are flushing huge quantities of cash down the toilet. Milage ratings for the various brands of synthetic oil vary, but you should get at least 3 months and 3000-5000 miles per change.

As Rlith said, a little white/bluish smoke is normal. A lot is not. If I read your post right, you're using 1/4 to 1/8 inch oil per month on the dipstick, which means that you would use about a quart in 3 months, is that correct?

A little oil in the PCV valve is also normal, however, Check the valve cover that doesn't have the PCV Valve for the Crankcase air intake line and also the related hose that should be connected to the air filter box and make sure everything is unplugged, open, and not pinched.

Valve Stem Seals are the usual culprit, but bad oil rings can cause oil burning too. Depending on where you live, you could try using a little heavier oil than you normally use and see if that helps.

[old_master]

What you are experiencing, more than likely, is the result of worn valve seals. Valve seals fit over the stem of the valve and keep, (excessive) oil from getting past the valve guides. When the engine is shut off, oil will leak past the valve seal, run down between the valve stem and valve guide, and accumulate in the combustion chamber. When the engine is started, the accumulated oil burns creating a blue cloud. After the engine has been running the smoke is usually not visible, unless the seals are extremely worn. Valve guides guide the valves as they move vertically up and down opening and closing. Valve guides also wear and as they wear, the clearance between the valve stem and the valve guide increases making it easier for oil to pass through. Hope this helps.

[BlazerLT]

Jimmy92W,

Smell you dipstick and tell us if it smells like gas.

Your cpi and nut kit could be leaking which could be diluting the oil with gas which allows it to easily go through the PCV system and into the intake where it is burned.

[DetroitMuscle]

Valve seals, check for TSB's the 1st gens have a standing TSB for the valve seals being bad, need the corvette style ones.

Its nothing to worry about unless you are losing oil and it burns it as well. I doubt the oil will smell like gas or be milky, you can live with it, or change the seals...and that isnt fun.

[JIMMY92w]

My post is accurate, except I rounded up the miles. Crank case hose is free. Do “oil rings” = piston rings? Heavier oil! I thought there was a post about this, which concluded to only use the specified oil (5w30). If heaver oil was used and the smoke stopped, would this mean bad rings?

No smell of gas, or milky oil.
Blazer LT, could you please explain how a leaking cpi/nutkit could result in gas in the oil. What path would it take? Thanks

Any estimates to what this would cost if I brought it to a shop to have the valve seals replaced? Is it true the one cylinder can be compressed at a time to lift the valve to change the seal, or do things need to be ripped apart?

Also can a backyard mechanic too this without spending too much time?

Thanks for the replies,

[BlazerLT]

There are two drain holes in the upper plenum down into the two middle cylinders. That is why you always see a fouled #3 plug when the nutkit leaks.

When the nutkit or the cpi leaks the fuel passes down into those two cylinders and past the rings into the oil.

[Rick Norwood]

Originally Posted by JIMMY92w

My post is accurate, except I rounded up the miles. Crank case hose is free. Do “oil rings” = piston rings? Heavier oil! I thought there was a post about this, which concluded to only use the specified oil (5w30). If heaver oil was used and the smoke stopped, would this mean bad rings?

No smell of gas, or milky oil.
Blazer LT, could you please explain how a leaking cpi/nutkit could result in gas in the oil. What path would it take? Thanks

Any estimates to what this would cost if I brought it to a shop to have the valve seals replaced? Is it true the one cylinder can be compressed at a time to lift the valve to change the seal, or do things need to be ripped apart?

Also can a backyard mechanic too this without spending too much time?

Thanks for the replies,

Yes, Oil rings = Piston Rings. On a standard Piston, there are usually 3 different rings. The bottom one is the oil ring. It is different in design from the other two rings, which are compression rings. If it was my truck, and normally used 5w-30, I'd try 10w-30 or even 10w-40 in the summer. If the smoking stops, it doesn't necessarily mean you have bad rings, it could be the valve seals too.

To answer your question about changing the valve seals without tearing the heads apart, the answer is yes. It requires a a special fitting that screws into the spark plug hole and an air compressor. The piston is brought up to TDC and this cylinder is pressurized with air. The compressed air holds the valve in place which allows you to remove the valve spring retainers after compressing the valve spring with a compression tool. The valve spring can then be removed and the seal replaced. Each cylinder is rebuilt in the same fashion according to the firing order. For a more complete description, this procedure is fully described in the Haynes manual for your truck, available at most parts stores.

[DetroitMuscle]

Get that tool and you can do it at home, its still a crappy job but the air tool makes it easier then using TDC on each hole to keep the valves in.

[old_master]

When compressed air is applied, the piston will go to BDC, both valves will close and the air pressure is what holds the valves closed.

[534BC]

Make sure it's on the power sroke. It is also possible to do it at tdc (power stroke) and may be safer , but may be more dangerous too. depends on the valve arrangement.

[534BC]

Here's something to try. Let that 1/8 - 1/4 oil leak/burn out and see if it stops using oil. It's cheap and easy to check.

Can one buy your drain oil? lol

[JIMMY92w]

Alright boys. Thanks for all the suggestions and information. I’ll dig out my manual, which for some reason I neglected to do. But will most likely let the shop tackle this. Just too damn busy!

But now I’m loaded with information and will be armed to handle those sleazy mechanics’

As for the oil it’s stored in a 20G aluminum beer keg. Please take her off my hands!


Cheers