My 03 SSEI was missing bad under full throttle and I did the following repairs;
New Air Filter
New Wires
New Plugs
Dropped the Cat and it had no blockage
-Minimal Improvement-
Changed the MAF Sensor and it fixed the problem
Drove 60 to 80 miles and it starts to run a little rougher and kicks the engine light on again.
Could a bad PCV valve cause excessive oil to get in the intake and get on the MAF sensor?
I have the stock intake system in place and keep new air filters in place. She has 175k miles but does not burn oil. With the new MAF she actually ran very strong like new.

Any Ideas?

-Mike-

Have you examined the MAF for contamination?

Not the new one. I am going to look at it Friday.
I was thinking about wiping it with a Quetip.

Don't use anything on the wire. Get some MAF Cleaner Spray from the auto parts store and spray the heck out of it and then let it air dry. If you touch the wire and damage it, you'll be crying when you find out how much they want for a new MAF.

What code do you have with that engine light? Try unplugging the MAF and driving like that. Does it drive better or the same? If the same then it'* not the MAF. Get that code and lets go from there.

The PCV is after the maf in the airstream and can not contaminate it.

X 2. Air filter, intake air temperature sensor and MAF screen are upstream from the MAF. Nothing that will throw oil.

Unless he has a after market air filter that has a oil coating. To much oil on those and it coats the MAF wire.

OOOH! Right you are. If he has a K&N or something like that, and over oils it ............

It use to have a K&N but I took it out and replaced it with a hastings stock filter. I never oiled it but had concerns the factory applied oil may been coming off the filter. I will get back in town tomorrow and see what code it is throwing.