New car blows a little smoke.

[NevadaSTi]

OK, I went and did it. I ended up buying a 1990 GT Mustang for $2800. After driving it around for a couple of days, I noticed an intermittent puff of blue (oil burning) smoke come out the tail pipes when starting from a dead stop. Also, it doesn't do it all the time, say maybe 50/50.

The motor (5.0), from what I was told has about 100k miles on it. When I am cruising around at highway or city driving speeds, I don't see any smoke. Even under full throttle exceleration I don't get any smoke.

So, I am thinking that perhaps a valve guide is worn out. There is some minor valve train noises, but nothing major. I actually hear an exhaust leak more then anything else. Oil pressure seams to be fine throughout the rmp range.

So, I guess the question is, "Is my assumption correct?" Or could it perhaps be that the motor needs a quick refreshing such as; rings, bearings, oil pump, etc? Could worn out rings be the culprit of the oil loading up and causing the smoke? Or does the car need the heads rebuilt?

I know, this is a subaru forum, but I am looking for some opinions from people I know.

[NevadaSTi]

I found this on Corner carvers. Not sure if it relates directly to my situation, but it might.

Originally Posted by GlennF at c-c.com

If it blows a pretty good puff of blue smoke on startup after a warm shutdown and a long sitting period it is most likely a valve seal/guide issue. If the smoke seems to get worse under higher load and RPM it is most likely a piston/ring issue.

Smoke while under load is due to ring flutter and oil entering the combustion chamber past the rings. This could be worn ring grooves in the piston, rings that have lost their tension or ring/cylinder wall wear issues.

Valve seal and guide problems are more evident during light load conditions when engine vacuum is high. High vacuum in the intake port coupled with crankcase pressure tends to draw oil through hard, worn seals or past valve stems with excessive stem-to-guide clearance. Decelerating in gear will also lead to smoking if this is the case.

Another thing to check would be to insure you have a good PCV valve and that the screen in the back of intake is in place. Wouldn't hurt to check that intake manifold bolts are tight as well.

[sperry]

Not to be a dick, but it's a 5.0 w/ 100k miles on it. That's kinda what they do.

I remember seeing AtomicLabMonkey's 5.0 do that anytime he jumped on it, and he never really considered it a big problem AFAIK.

[NevadaSTi]

AFAIK? What's that mean?

[k-dogg39]

Originally Posted by NevadaSTi

AFAIK? What's that mean?

As far as I know?

[cody]

Correct, IMHO.

[MPREZIV]

Sounds pretty regular to me... Really, it looks like it's either rings or valve guides, but not something that I would worry about really, unless you think you're gonna end up failing smog for it.

[NevadaSTi]

Cory, thats pretty much what I wanted to hear. I don't have to smog it, its registered in G-ville.

[AtomicLabMonkey]

Originally Posted by sperry

Not to be a dick, but it's a 5.0 w/ 100k miles on it. That's kinda what they do.

I remember seeing AtomicLabMonkey's 5.0 do that anytime he jumped on it, and he never really considered it a big problem AFAIK.

Troof.

When that car was still fairly new we asked a dealer about the oil consumption - they said that going through 1qt every 800-1000 miles or so was not uncommon for those engines. I guess they were just built a tad on the loose side. Just keep track of how much oil you're going through. Mine would usually need an extra quart added at ~1500 miles after an oil change. It can be burning the oil either from seepage past loose internals like piston rings, or it can get sucked through the PCV system from the lifter valley.

FYI if it has an aftermarket lower intake manifold & the PCV shield/screen are not installed correctly like on the factory lower manifold, the oil consumption will go through the roof.

[NevadaSTi]

Its only has an aftermarket TB that is way too big. 75mm to be exact. Other than that, it only has a BBK Cold air intake on it. Everything else is stock.

It seemed like yesterday, the longer I had waited at a stop light, the more smoke it blow once I got the green light. Its a little embarrassing.

[knucklesplitter]

I owned a couple 5.0's that I bought new (1988 Saleen Mustang #318 and 1994 GT). Brand new they both used a quart of oil between oil changes. The Saleen kept that up until I sold it at around 125k miles, but it never got much worse. Never noticed much visible blue smoke though.

[NevadaSTi]

I think I am gonna either redo the heads, or go with a set of aftermarket heads.

[AtomicLabMonkey]

If you're going to replace the intake along with the heads (which you should do all at once if you can afford it), make sure that you research the PCV issue I talked about. My Edelbrock lower didn't come with a PCV shield, so I figured I'd try running it that way. It started literally gulping down oil. So I pulled the intake back off, fabbed up a shield, re-installed, and it was fine.