# Blowin' Smoke in 4th and 5th gear!



## s14_drifter (Aug 21, 2006)

Hey Guys! I'm new to the forum and had a question regarding a little problem I'm having with my '95 240sx. Basically for the past 2 weeks when I drive my car on the freeway and I'm in 4th gear and reach about 3,000 RPMs and up my car begins to let out light blue smoke from the exhaust. When I shift to fifth gear it does it when I reach speeds of about 70 MPH. Right before it begins to smoke it makes somewhat a light rattling noise and continues to do so as it smokes. It only smoke in these two gears all the other gears(1-3) don't smoke at all in any RPM range. What can this be? I'm not too mechanically inclined. Thanks for any input and suggestions in advance.


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## Dustin (Dec 14, 2003)

hm, only in the top end gears, and 3k+ rpms.. that is odd, i honestly have no idea if it doesn't do it in the lower gears. i'd be inclined to say it's a transmission problem, except it's coming from the exhaust. i'm baffled.


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## rogoman (Dec 16, 2004)

From your description, it looks like the motor is burning oil.

You can verify that by first fully warming up the motor. Stand behind the car. Have someone rev the motor to 4,000 RPM and hold at that RPM for about 15 seconds. If you see a lot of blue smoke come out of the tailpipe, the motor is burning excessive oil; Time for new rings. 

As for the rattling at higher RPMs, it may be due to oil starvation or weak valve springs. Make sure the oil level is at the full mark. You might want to check the oil pressure.

You can check the pressure very easily by installing a temporary mechanical oil pressure gauge. You would remove the oil sensor which is located next to the oil filter and install the mechanical oil pressure gauge in it's place; you may need to get an 1/8 BSPT to 1/8 NPT adapter to hook up the gauge.

With the engine fully warmed up, the pressure should be as follows:
idle - at least 11 psi
3000 RPM - 60 to 70 psi


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