Check Engine Light After Air Filter Replacement

[Simo711]

Hi folks, I replaced my air filter yesterday on my 1994 D21 4x4. The old one was pretty dirty. Today, my check engine light came on while driving. No loss in power or anything else happened. I assumed it was because the new filter was allowing a lot of extra air through...so it is confused. Any thoughts without having error codes checked? Or, should I get these from autozone and report back?

Thanks, Chris

[Hawairish]

Hey Chris, normally an air filter won't cause any issues, unless you used a "wet" filter like a K&N. The dry filters should never be an issue, but if a K&N has too much oil on it, the oil can accumulate in the intake valve on sensors. If that's the case, it may have gotten on your MAF sensor, which would likely throw a code.

Still, throwing a code might just be coincidental. I'd go get a scan and report the code(s), then troubleshoot further. If the truck is new to you, could just be a couple small gremlins to sort out.

[mbonfan]

Intake Air Temperature Sensors (IAT)

IAT function
The Intake Air Temperature sensor (IAT) has been utilised as an Engine Control Unit (ECU) input signal from the very first EFI systems to the currently used systems, as a requirement for calculating the Air Mass volume for the incoming air charge. This is, to assist in determining the correct engine fuel requirement to suit the operating air temperature.

[whomadewho]

Check the vacuum hose located under the air cleaner. Although there is a bolt located near the fire wall that holds the air cleaner in place it’s possible when the clips were opened and closed or when the tube going to the air box was removed and replaced the vacuum hose came off?