A/C Observation ?'s info needed

[SigSaurP228]

I've had my explorer for a little over a month, and of course it would be the hottest month on record.

I have not had an automatic transmission vehicle in probably 10 years (my preference has always been manual transmission). I got this truck on the cheap 1996 limited 4.0 4x4 234,000.

I noticed that my gas mileage sincerely bites the big one. 12.5 around town with a/c on.

Last night on the way home at 12 am it was perfect 72 outside so I turned the A/C off. The Explorer ran about 500 rpms slower the whole way and its like the transmission found an entire new gear much slower.

I experimented a little on the way to work this afternoon.
45 Mph level ground AC on engine speed 2100 RPM Gas mileage 15 MPG
45 MPH level ground AC off engine speed 1650 RPM Gas mileage 21 MPG

Idle speed on the vehicle is high 900 in drive and 1000 in park.

The truck also seems to run below normal heat range leaving work at night it heats up almost all the way hot then drops well below half way and stays there. Unless under heavy acceleration then it heats up and drops again.

I am getting random codes from cel

Shift Solenoid 3
Oxygen sensor
and one other can't remember

I have cleaned the MAF sensor Map sensor. New IAC Valve, and Cam Position Sensor.

I guess my question is Is it possible that the AC is putting that much strain on the engine 500 rpms worth to keep the transmission from hitting overdrive?

 

[Lube]

It well may when coupled with the other issues you're having. It takes approx. 25 horses to drive the A/C compressor, so getting less mileage is normal. Not having as much available power is also normal, and the less power there is to begin with, the more apparent it becomes.
If you'll fix the other issues, it won't be so apparent.

 

[yavapaires]

I have a 96 4.0 OHV, auto, 4x4. It runs 21-2200 RPM at 65 MPH. So, I would guess you are driving around in 2nd gear, or possibly 3rd gear with the torque convertor unlocked. I would concentrate on getting the codes repaired then go from there. Where do you live. What is the temp? Mine doesn't seem to make any difference whether the A/C is operating or not. About 17-18 MPG town and highway. Around 20MPG on a trip, with A/C operating continously. Are you quoting ACTUAL MPG, or are you depending on the information center for the MPG?