4.6 Smokes, Help!

Here is my dilemma. I just recently purchased a '96 GT with around 140K on it. The car is in good shape and seems well taken care of. I have had it for about 4 months and just recently added an off-road H-Pipe and flowmaster cat back system. the other day, I was backing into my garage and when i gave the car a little gas, some blue smoke came out of the exhaust.

I have been observing the smoke for the last two weeks. It ONLY occurs under the following conditions:

1. Letting the vehicle idle for longer than 5 seconds, and briefly touching the throttle. it smokes blue for about 6 seconds then quits.

2. Doesn't smoke while cruising, full-throttle or cold startup.

3. Doesn't smoke untill the engine has warmed up a little, will not do it when the engine is cold and you let it idle then bump it.

4. Has consumed oil since day 1. Uses about 1.5 QTS between 3000 mile oil changes. I use a 5W30 weight oil.

5. Did not smoke untill the H-Pipe install, drove for several months before I added this, no smoke at all, although still used oil.

My only explanation is that the converters were cleaning up the exhaust enough that the smoke did not make it out the tailpipe. I DO NOT have my O2 sims in place yet, but the fuel mileage is really close to when it had cats, and the check engine light isn't on yet, although i know it will come on sooner or later.

I was in line for about 7 minutes in a drive-thru the other day, and noticed that it was smoking continuously toward the end of the wait, and smoked decently bad upon takeoff from the drive-thru, but quit once i got going down the road a short ways.

I'm thinking valve-stem seals. I have alreay replaced the PCV valve and checked the PCV system operation, all appears normal.

Anyone else have some ideas??

Thanks!

I'm almost certain on the limp-in mode. I have even warmed the car up, disconnected the battery and waited, then re-connected it and immediately re-started it and the smoke still appears. It's not like a blackish smoke, it's definately blue, and smells like oil, like running a weed-eater or something.

I've always heard the OHC motors consume some oil, but this is extremely visible, a decent amount of smoke on each puff, but not a major amount.

thanks for the suggestion, i really appreciate it, anyone else?

that's kinda what I was thinking. I was reading the service manual and doind valve stem seals isn't worth not puttin on the PI heads. I will just deal with it for another couple of months untill I complete my parts gathering and do the swap.

thanks!

Aghhhh, how I wish I still owned a pushrod engine, just thinking about how easy it would be to fix. But, the 4.6 seems to be a good motor, i'll just have to deal until I get the head swap done. but I hate that smoke

I guess it will all be worth it in the long run.

yea, with that compression that will definately be an issue. Although i'm not worried about the fuel mileage, I have another fuel effecient vehicle to drive. the stang usually just sees Friday night cruises and the track.

Although I have contimplated purchasing a complete '01+ longblock, as they don't seem to be hard to get ahold of for a decent price.

That would definately be much easier than a headswap.

git-it-83 said:

An engine swap easier than a headswap? Want to do my mechanical work for me?

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No thanks, i do enough mechanical work at my day job.

Yes, an engine swap would be easier, only because on the 4.6 to pull the heads you need to remove the motor.

You may read posts on people taking the heads off in the car, and it is possible. BUT usually results in scratching the cylinder head/block when installing/removing the heads resulting in a high pressure oil leak from the head gasket. In addition, since the head bolts on the 4.6 reach clear down into the main webbing of the block, making removing them in the car nearly impossible.

git-it-83 said:

Wow. I think you need to exhibit your talent (or toolbox) more, as most people I know of do the swap with the heart in place. good fo u!

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Oh, i'm well aware of it being done.

I can't actually say i've seen it done in the car, but I have seen PLENTY of cars come through the dealership with oil leaking from the passenger side head to block gasket.

'BUT I JUST HAD THE HAD GASKETS REPLACED 15000 MILES AGO AT BUBBA'S SHOP' they say.

Well, tell bubba's shop to read the Factory manuals next time.

Again, it can be done in the car, and it can be done successfully in car car, with no leaks.

But one false move, one slip of the hand, a little nick in the head surface and in the right place, and bam, oil leak. you get to do it all over again.

It is much more work, but I prefer not to take chances, after all, if I had to do my work over again and again I wouldn't have a job.

deftsound said:

sounds like its time for new piston rings..

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but if it was rings you would think that it would smoke all the time, under acceleration and such. It seems like it's only burning oil under a high manifold vacuum situation, ex. at idle.