dirkdiggle

iTrader: (1)

Wondering why My 2001 Lexus is Burning oil on startup?

I did do a AutoRx engine treatment recently
The car has used regular oil all its life and I switched to Synthetic on last oil change

I replaced the PCV valve recently. Seems the cold startup oil buring got worse after I replaced it......but my MPG have gotten much better since I changed it. from 19 too 24 mpg.

Maybe a faulty cheapo PCV valve?? .....it was only like $4 for metal one.
Or maybe synthetic oil cause this??

Lots of smoke on startup but none on restart after driving a while.

Using like a quart of oil every 500 miles.

Any help appreciated?

code58

If you're using a quart in 500 mi. you're using it all the time, not just on start up. Many people think the car is only using oil when it'd blowing smoke out the tail pipe like cars used to. That's not true any more. The catalytic convertor gets hot enough to burn the oil more thoroughly so it just doesn't SMOKE all the time. The smoke on startup is from EXCESSIVE oil in the combustion chambers from oil running down the valve stems past the seals when it's sitting or possibly also excessive oil in the PCV line on startup. NOT ALL PCV VALVES ARE CREATED EQUAL! I would #1- get that cheap PCV vavle out of there and put an OEM valve in. Cheap PCV valves can cause a ton of problems (I think of FRAM when I say that). #2- Do a search on problems caused by the original designed rear valve cover. There is a redesigned replacement. My personal feeling is that the AutoRX could only do you good, never harm and that I don't think synthetic oil is the problem either. BRAND of oil is sometimes the problem, try switching to another brand if the PCV issue doesn't seem to be the problem. Sometimes a particular car doesn't like a particular brand and acts up. Switching brands has corrected the problem many times. I don't know of anyone (including the oil engineers) who has figured out why this happens. Look at the PCV issue 1st! You might take the intake tube off and take a look in the throttle body (with the butterfly valves open). If you are burning that much oil through the INTAKE, it should show in the throttle body.

Baetke

Excessive oil consumption can also be caused by a plugged breather hose. Thats the hose that runs between the intake bellows and the forward(left) valve cover. If this line gets plugged the vacuum applied to the crankcase through the PCV valve will have to be satisfied by increased blowby past the piston rings and thus causing excessive oil consumption. Typically this will happen if the vehicle has been operated for a long time with a faulty PCV valve.

salimshah

There tests that can be performed .. Just stating the ones that have not been mentioned.

Compression test.
Valve leak down test

You can play with different weights of oil.

Salim

dirkdiggle

iTrader: (1)

Baetke do you have a pic of the breather hose you mentioned?

Baetke

Breather hose outlined in yellow.
When the vacuum applied by the intake manifold through the PCV valve exceeds the blowby rate in the crankcase, the breather hose provides the necessary air to ventilate the crankcase and prevent vacuum from building up. When the blowby rate exceeds the rate the gases are drawn out through the PCV valve, the blowby gasses will flow backward through this hose into the intake bellows. This happens during hard accelleration. That is why you will see some oily residue in the intake bellows. If the PCV valve gets plugged this will happen all the time and you will have a very dirty intake bellows and this can lead to a partially or fully plugged breather hose.

dirkdiggle

iTrader: (1)

Well that vacuum hose didnt seem to be clogged. Gonna try another new PCV valve I think.