Hello HT. I have a problem with my motor it is starting to blow some bluish white smoke only during high rpm shifts (8500-9k) the motor is from a 00 ITR b18c5, mild build 210ish daily driver, I don't beat on it very often and it sees mostly highway miles. I'm running Mobil 1 5-30w oil. So I am curious what could be the cause? I have done compression test and each cylinder 215-220ish. It does not smoke upon start up or anything only above 8500 rpms. I don't have a leak down test tool atm so not sure if the problem lies somewhere inside the head? Engine has a little over 100k now but has been rebuilt awhile back. Anyone have some input what I should be looking for? Thanks for any inputs!

 

My guess would be valve seals if the compression is still that high. Mine puffs a bit at high RPM but I know its tired rings. I'd just let the brake booster hose sip a few ounces of seafoam every few weeks until such time you want to redo the head.

 

Thanks, what will seafoam do for the valve seals if that is the problem?

 

Oh it won't do anything for the valve seals, it will just clean off the carbon that's going to build up from the leaking oil burning onto the valves*. Just watch your oil consumption and start setting aside money to refresh the head.

*In retrospect, putting the Seafoam in the gas tank would do the same thing.

 

If you performed the compression test correctly, your compression numbers are quite healthy if the bottom end, head gasket, and cylinder are factory parts. A leakdown test will only identify a compression leak, which according to your numbers does not exist.

Excessive crankcase pressure can allow oil to be forced into the valve guides through the seals. This is most common on the intake side of the engine, but can also occur on the exhaust side as well if the crankcase pressure is high enough.

If you have in any way modified the PCV system, excessive crankcase pressure can result in excessive oil consumption.

Bad valve stem seals are the root of the problem in nearly every case. Ensuring the PCV system is working properly will help reduce the volume of oil consumed. It is also inevitable in some high-rpm cases that oil consumption will increase.

 

Thank you for that info! I am running the factory PCV system with just a breather on the VC. I took a look at the canister on the back of the engine and it is covered in oil/gunk.

Also I just noticed today while I was exiting off the highway as I was coming to the light downhill, in 4th gear decelerating the car was backfiring quite a bit more than it used to and as I went back on the throttle lightly noticed some light blue smoke from the tail pipe? What indicator is this? I have no check lights or anything and everything else seems normal. I will run a leak down as soon as I can.

 

Back-firing is when fuel re-enters the intake manifold, and combusts. This is normally due to excessively advanced timing. This can break in the intake manifold, and can produce a hollow thud when it occurs.

After-burn is when fuel enters the exhaust, and is combusted. This can produce visible flames out of the tailpipe, and be accompanied by a lot of noise. This is caused by excessively retarded ignition timing.

A leak down test is not really going to tell you anything useful, because your compression numbers are even, and very good. The only real cause of oil burning from the piston rings is if the oil control rings are seized up. The piston moving as fast as it does in an engine like this will increase oil consumption by some amount anyways.

Remove the PCV valve and clean it. also reseal the flame arrestor (the black can) to the block. Using an over-sized PCV valve may help remedy this issue as it will reduce the amount of oil that can pass through the valve stem seals.

 

Thanks again for the help! It is definately backfiring, popping from the exhaust while I decelerate with light throttle I do believe my timing was advanced a bit during the tuning but will it harm anything if this keeps up? Also, I will be looking into the PCV system as you say since my compression numbers are still decent, the black box and line connected to it are really gunky and could use a cleaning too. Hopefully that will help out a little cause I am having to check/add oil more frequently. Do you recommend upgrading from the oem setup to performance setup?

 

Upgrading the PCV system can cause idle quality problems, as the additional air will interfere with IACV. Technically, enlarging the PCV system is a vacuum leak.

Popping from the exhaust is after-burn, not back-fire. Read my post above. Timing that is retarded will cause this issue, along with, in some cases, excessive fuel delivery.

 

If you want to upgrade, a proper catch can would not be a bad thing as long as the iem pcv is still in play. Go to the dealer, get a new oem pcv, and put that between the catch can and intake manifold; you will still have the same vacuum leak as stock that way.