General Motors notes that the use of an aftermarket oil-bath air filter that is excessively over-oiled may result in any of the following:
- The MIL may be on accompanied by a DTC.
- The automatic transmission may shift early and/or late, slipping and/or damaged clutches or bands.
- Engine drivability concerns such as but not limited to poor acceleration from a stop, stumble, rough idle and/or limited engine RPM range.
The oil used on the air filter elements may be transferred onto the mass air flow (MAF) or mass air flow/intake air temperature (MAF.IAT) sensor, resulting in contamination and poor performance.
The contamination will result in the grams per second (GPS) signal and/or the Hertz (Hz) frequency signal from the MAF or MAF/IAT sensor to be skewed, low or generally out of range. The Hertz and/or grams per second parameters on the scan tool should be compared to a like vehicle with an OEM air box and air filter under the same driving conditions to verify the cause of the concern.