Hello all,
This is my first post here although, I have been helped out alot by just searching old posts. I have a tbi system on this and what happens is that when it starts up it is getting way to much fuel to run. You would have to hold it wide open to start. It was throwing an o2 error code and a coolant temp sensor code.I have checked all vacum hoses with ether and all sensors and circuts to ecm are good.I have replaced the O2 sensor, computer side coolant temp switch, seemed to be wet around the fuel reg assy-replaced the top of the tbi + reg, cleaned the tbi in and out new gaskets, my scanner picks up no codes and all diagnostics through it are ok. I have a Mac tools edition genysis up to 99 pathfinder. Its almost like that the ecm forgets what it supposed to do. after the o2 and the ect replacement it ran fine the after it sat from running about an hour same thing happens. But it is very intermitant getting worse. While in diagnostic mode it cycles from lean to rich very rapidly. Any ideas would be helpful, thanks.

 

Well I had a similar problem with mine and from just a couple of days worth of driving it (very rich) the carbon plugged up the converter. I would try just disconnecting your converter and see how it runs. That may be the answer.
Jack

 

What is the fuel pressure reading?
How many miles on the engine?
Something is causing too much fuel to be introduced into the motor and the ECM is trying to lean it out but it is out of range; this is why you are getting the rich then lean readings and the ECM is acting confused.
This condition is nornally the result of a part failure not a faulty sensor.

First check the easy things like the PCV system alos disconnect the evaporative hoses and see if the over-rich condition goes away.
Then move on and check for a dirty (stuck open) fuel injector(s) or a faulty pressure regulator.

 

Fuel press. is within range. Disconnected the evap and readings stay the same. It was a brisk 45 degrees tonight and actully we are goin to set a 7 year record for south florida in the morning. I came home and it fired right up. went on through the warm up and it is actully running great. With 150000 on it i think im goin to ship it back to my friend to drive. I drilled a hole and scoped the inside of the cat out and its pretty carboned up. he is goin to go and have a straight pipe put in it this weekend.i cleaned the tbi and put a new top half on it with the reg assy in it. the injectors are pretty clean. the screens on them were clean and new looking. replaced those anyways. I thank you both for the posts. HAPPY NEW YEAR