91ls400own

OK Guys, I have a 91 and a 94. All ok with 91, runs 55MPH at 11 or 1200 RPM
BUT the 94 runs at twice that example 1500 at 45 MPH and 2100 at 60 MPH.
When I turn off the OD Button it does down shift. What maybe my problem?? Burning way too much gas!
Thanks

mista808

When you turn off the OD, it is supposed to shift into 3rd from 4th.... people usually turn off the OD when cruising around town, and turn it on when driving on the highways and byways.....

gmacrae

no LS400 will do 1100-1200rpm at 55mph - if your car is telling you that, either your tacho or speedo is way off. About 2100rpm is right for 60mph/100kmh.

91ls400own

While my 94 shows around 2100 RPM at 65, my 91 shows 1150 - 1200 RPM at 65 AND GAS MILEAGE IS 18 TO 20 mpg WHILE THE 94 GETS MORE LIKE 12 mpg ON hwy! wILL HAVE THEM BOTH CHECKED OUT. wONDER IF THERE IS A CHART SHOWING WHAT RPM SHOULD BE AT WHAT SPEED?? THAT WOULD HELP.
tHANKS FOR YOUR TIME AND RESPONSE
mARCEL

gmacrae

You cant accurately say how many rpm you should be doing with the auto because the torque converter can be locked and unlocked in overdrive, with differing amounts of throttle this can make the revs vary roughly 400-500rpm. But if you're cruising at 60mph with very light throttle, the TC should be locked, and you should be around 2100rpm - your 91 is reading wrong for some reason. Your 94 could benefit from a full service/tune up (trans included), and possibly replacement water temp sensor, maybe 02 sensors - have someone check both cars for error codes first.