# torque converter not locking in overdrive



## noackrite (Dec 23, 2009)

hi, i am new to this forum so, hi and thank you for any help. i have a 91 sentra . i bought a used trans about3 years ago. i have put about 200 k miles on it . i deliver newspapers out of this car. i have changed the fluid in it about 4 times already.
i noticed about 3 weeks ago my gas mileage has been dropping. engine runs great...the other night i am coming home from work at night and i am enjoying the hum of my exhaust leak and then while crusing at about 70 mph for at least 5 miles,the trans shifts and RPM's drop.
i am thinking that the converter is not locking up when it is suppose to.
i have not cleaned the filter. i will do this as soon as i can
could it be the shift silonoid ??(spelling )
thanks again for any help with this.

Randy


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## sunnysentra (Jul 24, 2002)

Here is what I know. The automatics will not shift into overdrive if the Engine Temperature sensor goes bad. it will not throw a light, so you never know. Do you know when the engine is cold, you cannot go into 4th gear? until the engine is at the operating temperature. The sensor tells the engine, OK, I am ready, you can engage your fourth gear. This is to allow the engine to heat up faster to operating range before cruising. 

OK, The sensor is located on the passenger side. look at the intake manifold. its located on the lower part. YOu will see a RED plug top. The sensor screws into the intake. unplug the harness, get a socket and remove this. Nissan sells this part. here is the courtesy part #. its 25 bucks. 

ENGINE COOLANT TEMPERATURE SENSOR - Sentra (B13) 1991-1994 :: Nissan Parts, NISMO and Nissan Accessories - Courtesyparts.com

merry christmas. 

Chris


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## noackrite (Dec 23, 2009)

thanks chris. that is very interesting .but..... the car shifts into 4th gear, it just dont lock up the converter. i drive the car for about 60 miles while i am delivering newspapers then i get on the highway to go to my 2nd job.....but.... for some reason today , it shifted into overdrive and it also locked up the converter when it was supposed to..... go figure !


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## sunnysentra (Jul 24, 2002)

mmm. I will look in the FSM under trouble diagnosis. interesting. must be the torque converter switches to lock up the converter that is malfunctioning. I bet its one of those. 

Chris


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