I posted a thread a few days ago about replacing my valve seals due to smoke on start up. From the seals on the #4 cylinder being totally toasted, the top of the piston was layered in what appears to be charred oil. I also replaced the PCV valve which was completely stopped up. I didn't pull the heads so I planned on Seafoam'n it and driving it a while letting the piston clean itself off. Well, car is Seafoamed and about 200 miles later, absolutely no difference in build up on the #4 piston and it is still fouling new plugs, covering them in black oil and throwing the P0300 code within 20-30 miles of a plug change. ALSO, it is STILL smoking but only on warm start ups now. If the car sits long enough to completely cool down it doesn't smoke at all on start up. If I start it within an hour or so of being driven, it'll smoke blue for the 3-5 seconds. And it is also still using a qt of oil every 200 miles or so.

Here is the lower intake runner to the #4 cylinder. (not sure if I posted pics correctly)

I also had what I consider a significant amount of oil residue through the upper intake plenum that I assume was from the pcv valve being stuck and allowing oil to blow back into the intake.

Here is a pic of the top of the #4 piston. All other pistons were relatively clean with only slight discoloration.

To recap what I've done so far: new valve seals, timing chains(pri and sec) since I already had the cover off, timing chain tensioners, valve cover gaskets, upper/lower intake gaskets, checked out all coils, replaced coil plug boots, plugs(constantly) and pcv valve. I'm about at my wits end trying to narrow down the source of the oil smoke. About the only thing left that I believe is left to do is rings. Could someone please please please tell me that I am leaving something out of the process of elimination before I get to having to completely tear the engine down?

 

Sounds similar to what I was experiencing with my previous motor. Motor started to run like crap after leaving work one afternoon. I changed out the spark plugs, checked the coil packs and after performing a compression check it turned out my #4 cylinder was getting significantly lower compression readings. I poured some oil down through the spark plug hole to try to determine if it were the rings or seals. Compression didn't increase so it was a good chance it might be the seals. I got lucky and a forum member was selling a DE motor with a spun bearing for $300 but the heads were good. I ended up getting the motor just for the heads. I pulled the left bank head and found one of the exhaust valves had a piece of it missing. In my case, replacing the head would partially solve my compression problem, the piece of valve that broke off had fragmented into smaller pieces and one got lodged between the cylinder and piston causing a gouge to run up and down the wall. I did put the motor back together with the replacement head and ran it sometime but I eventually swapped out the motor. I'll post pics of the head with the bad valve when I get a chance.

 

I did do a compression test on all 6 but didn't do a leak down. All 6 dry were 169-172 with the problematic #4 cylinder being the 172. After searching on here a bit more I read that the #4 injector could POSSIBLY be giving me the trouble. Something to the effect of the injector being stuck open and dumping gas into that cylinder when you turn the car off, the gas will sit on the piston seeping past the oil control rings and if the car is started up before the gas is evaporated than it will allow some oil blowback through the oil control ring and into the intake until the gas is burnt away from it and the ring reseals itself and of course buring that gas/oil mix from the intake. Which could explain why it only smokes if the car is started within 30 minutes of it being driven and why cylinders 2 and 4 have that build up in the intake runners and minute traces of oil in the upper plenum.

Have you ever heard of something like that or would this even be considered a possibility?

 

If an injector leaks fuel into the cylinder overnight, for instance, the car will probably have a more difficult time starting and will emit either grey/black or blue smoke.

In your case though I'd think if it was only leaking a slight amount the burn off would be quick and the smoking would cease almost immediately. If it was leaking a large amount of fuel then your oil would be heavily diluted with gasoline, the smoke would most likely be blue, but I don't see why it wouldn't end almost immediately as well. If the smoke continued, I'd think the injector would have to be static (stuck open) while the engine was running, in which case the engine would perform horribly at all times.

 

The only issues other than the start up smoke is if I take it above 4k and close the throttle real quick, itll stumble for a split when it comes back to idle. Other than that, it runs great. I'm on the verge of just yanking out the VQ and dropping a carb'd 350 in it!

 

I'd definitely check the injector just to verify if it's operating properly or not.

 

Off topic here but, when you pulled the heads to swap them out, did you have to have them machined/planed before bolting them back on? I've heard some say that when untorquing aluminum heads that it is almost a guarantee that they are going to warp some and should be sent to a machine shop to be planed to get them true flat again. But, have also heard some people say they'll "flatten" back out when you torque them down again. Any insight on this?

PS. Thanks for your help and input so far with my issue!

 

Per the rationalization you provided, I have not heard this but then again I'm not a machinist or an engine builder either. I can see taking the heads to the machine shop if there is evidence of warpage due to overheating but I thought this was more common with motors that have a cast iron block and aluminum heads. I really can't see how the heads can warp by just un-torquing them from the block, well assuming if it is done per the FSM. As there is a specific sequence when torquing down a series of bolts, usually when removing a component the bolt sequence is opposite of installation.

Sorry if I'm preaching to the choir here... When I have to do this I typically do enough to break the tension on the first bolt then work my way to the others. Keep in mind, these bolts are still pretty smoked down. After I break the tension on the last bolt I work my way back to the first in the sequence and loosen it up just a little bit and work my way to the others. I repeat this a little more every time till all the bolts are loose. It's tedious but I'm a meticulous person and what I do might be unnecessary.

In my case I did not take the head to the machine shop. I believe I checked the mating surface with a straight edge per guidelines provided in the FSM. If there is suspicion of warpage i don't understand why someone would reinstall them without getting them planed. I would expect that torquing them down to remove the warpage would throw off the torque requirements.

 

I was asking about the head removal/warping issue because just to eliminate one more thing I was going to pull the heads to check for a burnt exhaust valve and to also put in new guides.

BUT, no need to do that anymore. My brother's friend came over this morning and ran a complete diagnostic with his Panasonic Toughbook and also did a leak down test for me. #4 injector was stuck wide open and #2 injector was giving some issues. I was quite thrilled with that thinking that was the root of my problem. He wanted to do a leakdown test anyways just to check the oil rings. All 6 cylinders turned out good!

So come this week end, I'll be doing injectors and HOPEFULLY I'll have this problem licked! I'll update after I get the new injectors in!

Again, a huge thanks for your insight!