i need help on my 91 ford explorer

[monkeybam]

i have a 91 ford explorer 4.0 4x4 xlt and i put a new used engine in it and it was revving at 4000 rpms. i found a vacuum leak on my brake booster. it is now revving a 1500 rmps put im only getting 10 mpg but before i put the new motor i was getting almost 20 mpg?

 

[Pablo Sanjines B]

Hi.
The average mpg for a exp 1991 is 18 (highway) and 14 (City).
You can check the followin tips:
check the air filter, if it is clogged or dirty you will need to replace it. Low presure at the tires. Inspect your binding brakes. Fuel leakage check conections, lines and components. Dirty or clogged fuel injectors, Fuel injection or engine control systems malfunction, Thermostat stuck open or not installed, Improper operating transmission.
good luck.

 

[monkeybam]

when at idle it is revving at 4000 rpms i clean my throttle body and its now idling at 2000 rpms, i checked all my vacuum lines and there is no leaks, i tryed to clean my idle air control valve but its still dirty. does anyone have a clue why it is still revving high?

 

[Pablo Sanjines B]

I found the following info, It is not the same explorer year but maybee it can help, good luck
http://www.explorerforum.com/forums/showthread.php?t=77235