For some reason my 4.0 96 Cherokee won't pass PA emissions. I have a bad front o2 sensor. Any ideas on how to make it pass? I have a knock in the engine that my mechanic claims is the lower crank shaft floating but he hasnt taken it apart.

Thanks in advance

 

Changing your front O2 sensor would be a good start.

 

Will do. Does running fuel injector cleaner help ?

 

Whys it failing?

The sheet usually tells you why...

 

O2 sensor/ high voltage on fuel sensor

 

Wow.

 

replace ur o2. disconnect batt. for 30 min. reconnect batt after 30 min. then go for freeway drive, drive about 60 miles, get it warmed up and carbon and fuel burnt out and sensors all set. If ur chk engine light is on, u will not pass. Dont know how PA does emissions, plug n play with ECU, or tail pipe test.?
I do emissions in Nevada. so hit me up with QnA. i will try n help as much as possible.