Smoking 3.8 Grand Prix

[freefalcon]

Greetings everyone,

I have one here I want to throw out there in hopes of someone having an idea or suggestion that might help us on this vehicle. The vehicle is a 2007 Pontiac Grand Prix, 3.8L eng, 114500 miles. This vehicle is owned by a used car lot that is a customer of ours. Let me give you some history before I go into the immediate problem. Car came into the shop 3 months ago with a misfire & check engine light on. We found low compression on 2 cylinders and leakage past the valves on those two cylinders. Heads were removed and sent to machine shop to be repaired, which they were along with new valve seals. Reinstalled heads with all new gaskets, car ran great and was released. Now the car is back and is smoking. The car has been on the car lot and probably not driven over 100 miles since initial repair. It runs good, no misfires, no check engine light but it was smoking at idle and if reved smoked more. Here’s what we’ve checked so far: PCV valve replaced, cylinder compression check all good at or near 200, cylinder leak down checks all cyls tested good, injector balance test all within specs, fuel pressure leak down check within specs, coolant pressure test holds pressure no leaks found, performed smoke test with smoke machine to see if perhaps we had a leak on the intake it checked good, spark plugs look good no signs of oil or fuel excessive burn, removed valve cover to check valve seals in case one had slipped off nothing there. Then I drove it 40 miles for about an hour when I returned to shop it wasn’t smoking at idle but still would smoke when reved occasionally and the smoke has the blueish tint of burning oil. So what do you guys think?? Valve guide possibly? rings? I’m going to let the cylinders soak overnight with seafoam and recheck in the morning but hoping to see if anyone else has an idea of something we can check before just doing a tear down again if it’s still smokes after the seafoam treatment.
Thanks in advance.

Topic

[Its me]

This reminds me of a story I heard about a new car that constantly smoked… I don’t know how true it was but it goes like this:

New car was bought and it constantly smoked. Took to the dealer and no one could figure it out… They checked everything (like you did)…. Couldn’t figure it out.. Were about to give the guy another car and declare it a lemon when….

An old Tech realized…. It had the wrong dipstick in it….

It was overfull on oil!!! 😛

I don’t know if that is your issue, but I would look at it!!!

Cheers!

[freefalcon]

Nope oil is at proper level 😉

[Walter Cheryba]

Was it smoking before the head work was done? If not then I’m suspect of the shop that did the head work. That is the biggest change you speak of. I’ve been victim of the wrong valve seals and or valves being used by a trusted and reliable machine shop. It happens.

[college man]

Try doing a wet compression test. If the compression improves
substantial then rings are at fault.

[Daniel]

I’m with Collegeman. If it smokes when reved then it’s prob rings. If the valve guides were bad it would smoke at start-up but not much when reved.

[Walter Cheryba]

Agreed, BUT what IF the seals are wrong?

[Daniel]

If there was a problem with the valve guide seals you still should not have plumes of blue smoke while reving the engine. It’s almost impossible to install the wrong size valve guide seal.

[Walter Cheryba]

I’m not here to argue, just trying to help same as you are. I can only go by the info given in the forum, in this case there was no mention of smoking prior to the head work being done. A ring problem could have developed after the work was done although the time frame is rather short. Someone could have been drag racing the car after the work was done for all I know and injured the engine. And while I agree that it is almost impossible to install the wrong valve guide seals I had it happen to me twice. It created a lot of sadness, expense and unhappiness.

[Daniel]

I’m not being argumentative. You asked me “what if the seals are wrong” and I stated that if the seals were wrong you should not get smoke when you rev the engine. I apologize if you thought I was being rude.

[Walter Cheryba]

Thank you for that-no apology needed-it is all good. B) Now-where is freefalcon with an update?!?

[Bill]

It could have the intake and exhaust seals on the wrong valves. I have been there and done that.
If enough oil is getting down the guides it will smoke anytime.

[freefalcon]

Sorry it took a few days to get back to you guys. Thanks for your replies. Well in addition to what I posted already I performed a cylinder leakage test on all cylinders and it too was good. So I put seafoam in the cylinders and let it sit overnight, really not expecting much, but did it anyway and now it isn’t smoking. Of course after the seafoam treatment it smoked like a freight train for the first hour. The only thing I can think of is the car sitting idle on the car lot for several months perhaps one or more ring became stuck especially since it wasn’t driven much after replacing the headgaskets originally. I’ve had that happen with rings becoming stuck before but usually I could isolate it down to which cylinder by certain signs. This particular car wasn’t giving us much. Anyway thanks for everyones input hopefully we won’t see this one again.

[Author]

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