running rough
 

Hello Mercury forum, looking for a little input on a problem with my 96 Cougar. Car has 218000 miles, 4.6 litre V-8, is in excellent shape for its age. Fires right up and idles fine (meaning it will sit there and run with out giving the motor any gas). My problem is that when the car has been sitting for a few hours and the engine temparature is cold, when you first start it and let it run it will start to run rough, however if you just let it sit and get to operating temp it runs just great. I was wondering if anyone has experienced a similar problem and what was done to solve it. My thoughts at this point are maybe one of the sensors (i.e. oxygen), but I am looking for any input anyone may have.

plugs wires (when were these replaced last?) throttle position sensor may have cold issues, mass air flow sensor may have cold issues, oxygen sensors may not be heating properly (I think this one is the most probable if your sensors are original as they're the self heating kind I think). If it's not the oxygen sensors, plugs or wires, then look at the MAF sensor.

Hello slymer, thank you very much for your input, it seems we are on the same page. I just changed the wires about a month ago (I have had issues with wires before so that was my first thought-plus I have lifetime warranty wires so that was a cost effective change), I have also checked the MAF, disconnected it and drove for a day or so, my mechanic and I came to the conclusion that is not the problem. I am leaning toward the oxygen sensors, as I stated before, once the car reaches operating temp everything is fine, it runs like it has 18000 miles, not 218000. Can you tell me if the only way to check the sensors is to take it to a shop and have it hooked to an anylyzer? Thanks again for your reply and your suggestions, it is greatly appreciated.

96Cat

as far as I know that's the only way to check. You can do a check on the heater wires inside the sensors if you have an ohm meter. I'm not sure which wires to probe though.

Thanks again slymer, I appreciate your help.