Need help with 4 cylinder running rich

[pitbull4x4]

A friend of mine has a 87-88 MJ with a 4 cylinder that is running rich. Every 2-3 weeks it starts fauling the plugs. He is going to put a new fuel injector in. Would this take care of the problem?

[Geonovast]

Maybe.

 

Replace the O2 sensor first. That's usually the cause of it running rich.

[pitbull4x4]

Thanks for the help.

[BLHTAZ]

Maybe.

 

Replace the O2 sensor first. That's usually the cause of it running rich.

Agreed--it's not likely that the injector would be the cause of the trouble. There is something sending to much fuel, and the o2 sensor is the first thing on the list of suspects.