93gc40

In the morning when driving at 65 the RPM is 2000, in the afternoon the RPM at 65 is 2300-2400. Afternoon temps are in the 100's, mornings are are in the 70's. What is going on????

I do have a possible 1st gear solenoid issue, the first shift, of the day, from 1 to 2 is very slow, have to lift to get it to shift out of 1st, sometimes. Will shift normally until the next morning. Engine temps are normal, goes to a needle width below the 210 mark and stays there. Unless in heavy traffic or climbing very steep hills, then will climb up, but returns to normal when things speed up or level out. Tranny fluid has less than 1000 miles, filter less than 5000 miles.

djb383

I suspect the electronic tach is in error however 300-400 rpm is about the rpm difference between the torque converter be locked and unlocked.

xjmarc

How high do you have the AC in the afternoons cause it could make the engine run a bit harder.

93gc40

I suspect the converter, also. Just not sure.
AC is ON at all times, fan at 1 or 2 in the morning 3 or 4 in the afternoon. I run my AC 24/7/365, even in Winter when it's 30-40 outside.

kohlers89XJ

well the increase in fan speed could be that reason for increased RPMs tomorrow try to run it at the same speed all day and see if theres a difference

xj_maniac_newb

at least you have a tach to look at. . . .

codfish

Air is thinner when it is hot. You will have to intake more air into the engine (higher RPM) to produce the same power as when the air is cooler.

Codfish