I have a 98 xlt with the 2.5L with 135K. About 6 months ago I got a check light that went on and the code was port 1 running too lean. I also think that it has read both port 1 and 2 runnig too lean. This has now happened 3 or 4 times.

So far I have:
cleaned the mass air sensor 3 times.
checked the spark plugs
run 2 bottles of luckas fule system cleaner
and repalced the O2 sensor

From what I have read different places it sounds like this is a hard issues to solve. But any thing would help!!

 

Make sure you have adeqaute fuel pressure. Should be 35-40 key on engine off and 30-35 engine running. It may be a weak fuel pump, injector issue, or your fuel pressure regulator.

 

when was the last time you changed your fuel filter? if you aren't getting enough fuel it could cause you to run a bit lean.