Got a problem. Took my 95 grand cherokee limited to an ac shop for repairs. AC works great but now it is running full rich with a code 51. Also cannot pull codes with a reader unless I enter it as a 94'. Some advice would be greatly appreciated. Bruce2

 

When was the o2 sensor changed?

When was the last tune up done?

 

Thanks for the response. The 02 sensor was replaced a year ago and the last tune up was done about 3 years ago. Bruce 2

 

Hi Bruce. What engine is in your ZJ? What repairs were made to the air conditioning system, exactly? Was there any period of time between the repairs and when the problem presented itself? Was it immediate, the same day, several miles?

-Rod

 

Rod, Thanks for the response. My daughter drove it home from the ac shop and didn't really think anything of it until my wife drove it the next day. She told me it was running worse than it ever had. We've had it about 8 years. It passed smog last summer. It has the 5.2L engine.
Bruce2

 

May be time for another tune up, the owners manual recommends a plug change every 30k. I recommend plugs, wires, cap, rotor, and all of the filters.

 

I'd agree with the tune-up. Pay close attention to what the plugs look like, and keep track of what cylinder they're from. Just keep an eye out for the usual, particularly if they are oil or gas soaked. I could be wrong, but isn't the 51 code for 02 sensor indicating lean? Check the battery terminals, too. Please let us know what you find.

Edited - Also, take a look at this, it may help you with the diagnostic process. http://www.allpar.com/fix/codes/faults/code-51-52.html

 

I agree you might need a tune up but just curious, what did they do there to screw you up do much. You said before the ac shop your engine was fine and had no issue? Just curious maybe you should go under the hood and make sure they didn't disconnect anything, burn anything etc. take pics of smoke and o2 connections even a plug too. Just saying