Blazer Forum - Chevy Blazer Forums

GM's mass air flow sensors are very sensitive. The newer the vehicle, the most sensative they are and the more systems that can be affected. Although I do not have a K&N on my Bravada YET, I plan on it. I can tell you that a previous owner HAS had a K&N on it and that was mainly the reason why I picked it up so cheap! Whenever I change my oil on any of my GM vehicles, I clean the MAF. A can of electrical parts cleaner is all you need to use. In the case of the inline MAF sensor used on all blazers (IIRC), you may or may not have to take the MAF apart to clean it. Mine was so dirty that it required me to use a q-tip with some cleaning agent on it to clean the elements. BE VERY CAREFUL if you do this. The elements are VERY VERY sensitive and are barely held on. If you use the right cleaner, you shouldn't need to put any pressure on it at all. While you are cleaning and have the MAF apart, take some carb/throttlebody cleaner and spray the MAF screen from various angles to clean it.

Driveability concerns can go as far as to screw up a tranmission in the worst case scenario. The MAF sensor has a lot to do with how, when, and how fast a shift happens. When they get gummed up, the readings are lower and the PCM will soften up the shifts (more slip) by decreasing line pressure. This can cause premature wear in the transmission. It also affects the TCC engage and can cause premature failure of the torque converter.

Always check your K&N filter for over oiling. Even K&N filters out of the box can be over oiled! I have made it a habit to run my shop vac over the filter before reinstalling it. That goes for filters out of the box and filters I have cleaned and re-oiled. These filters only need a sparing amount of oil on them (just enough to give them a red tinge).

There is a TSB (technical service bulletin) on this:
[code]A/T - Shift/Driveability Concerns/SES Lamp ON
Bulletin No.: 04-07-30-013A
Date: January 25, 2005

INFORMATION
Subject:
Automatic Transmission Shift, Engine Driveability Concerns or Service Engine Soon (SES)
Light On as a Result of the Use of an Excessively/Over-Oiled Aftermarket, Reusable Air Filter

Models:
2005 and Prior GM Cars and Light Duty Trucks
2005 and Prior Saturn Models

Supercede:
This bulletin is being revised to add additional model years and to clarify warranty coverage.
Please discard Corporate Bulletin Number 04-07-30-013 (Section 07 - Transmission/Transaxle).

*Image that says*
Do This - First check for an aftermarket excessively over-oiled air filter
Don't Do This - DO NOT replace the MAF sensor under warranty if the concerns result from the use of an
excessively over-oiled aftermarket reuseable air filter

The use of an excessively/over-oiled aftermarket, reusable air filter may result in:
^ Service Engine Soon (SES) Light On

^ Transmission shift concerns, slipping and damaged clutch(es) or band(s)

^ Engine driveability concerns, poor acceleration from a stop, limited engine RPM range

The oil that is used on these air filter elements may be transferred onto the Mass Air Flow (MAF)
sensor causing contamination of the sensor. As a result, the Grams per Second (GPS) signal from
the MAF may be low and any or all of the concerns listed above may occur.

When servicing a vehicle with any of these concerns, be sure to check for the presence of an
aftermarket reusable, excessively/over-oiled air filter. The MAF, GPS reading should be compared
to a like vehicle with an OEM air box and filter under the same driving conditions to verify the concern.

The use of an aftermarket reusable air filter DOES NOT void the vehicle's warranty.

If an aftermarket reusable air filter is used, technicians should inspect the MAF sensor element and the
air induction hose for contamination of oil prior to making warranty repairs.

Transmission or engine driveability concerns (related to the MAF