I have a problem with my 1992 jeep cherokee laredo 4.0L with with auto4wd. It acts like its misssing, replaced oxygen sensor still problem, get code readings 15 , I know thats the speed sensor and speedometer hasn't worked for a year but alwasy ran good with that problem, but do have new code 41 Alt. field, will this cause the jeep to miss fire. The alt. is charging like it should got any answers for my mechanic please.

 

There's a lot of things that will make an engine not run right, but in the end, the engine really needs three things. Spark at the right time, Fuel at the right time, and Compression.

Try these:
Check/Change the fuel filter. If you don't know when it was done, do it.
Run some Lucas Fuel Injector Cleaner through
Check/Change the Spark Plugs. If you don't know when they were done, do them.
Check/Change the Distributor Cap/Rotor. Again, if you don't know... do them.
Check/Change the Spark Plug Wires.
Check for vacuum leaks. They make a whistling noise.