Expert: Von Sudderth - 11/4/2009

Question
QUESTION: Hi, I have a 1996 Nissan Altima GXE, 4cyl., 2.4L  Mileage: 210,000
Just recently bought the car. Seems the RPM's are a little high..the tach reads 1000 at idle and 4000 at 60 mph. Is this normal? It seems to have no problems otherwise; it shifts properly and no burned tranny fluid.
Thank you.

ANSWER: John,

Two things here.  First, the idle air control valve probably needs to be replaced to get the idle down.  The second is the overdrive is probably not working if you are taching 4000 at 60 miles per hour.  Turn off the overdrive and see if the RPMs go up.  If not the overdrive is not engaging.  If that is the case the temperature switch or vacuum switch is not working to let the transmission know to shift into overdrive (4th gear).  Or, the lockup torque converter is not locking up.

---------- FOLLOW-UP ----------

QUESTION: Thank you for the helpful information. I'm a new driver and not familiar with the overdrive and I've never used it at all so I guess it explains the high rpm.
When should I use the overdrive? Thanks again.

Answer
John,

Leave the overdrive on at all times as it helps with mileage and if you turn if off the car will burn out the transmission over a period of time.  The only time it should be turned off is when you are climbing mountains and the car shifts from fourth to third and back and fourth.  This is just as bad as leaving it out of fourth.  Fourth and overdrive are the same thing so just remember to leave the transmission in drive with the overdrive button on.