Air Filter Casuing A Lean Condition…
CEL is on, pulled codes and found p0171, run VE test found low cleaned and it came up, replaced and higher, see attachments, removed aftermarket air filter nd found fuel trims drastically reverse back to normal. i have never seen a filter take an engine lean, what am i missing
When I read the e-mail I thought for sure it would be a Nissan. Is the MAF near the air filter? I think you probably nailed it. Irregular air flow from aftermarket air filter causing the MAF to read low. I do not have a physics degree or understanding of air flow. I would assume the air filter is creating a situation where there is little air flow in the space the MAF is sampling.
Interesting. was the aftermarket air filter very soft?
Was it a k&n . I have seen this a lot with that filter
Turbulence. , The factory plumbing with air filter smooths air and is channeled over the sensors hot wire. Had two domestics that one was missing clamp to keep the two halves together- Windstar. The other was a G series gm that was missing the air filter element, housing was intact. Installed element, fuel trims normal. My opinion anyway given my experiences.
If the filter design changes the air flow pattern that goes up to the MAF, it can easily skew the trims. In my lifetime, I have only seen one or two filters do that. If you get in the habit of test driving cars while using a FRTD, you will pick out a lot of issues like this. The issues might not be causing a CEL, or driveability problems, but they are still there. You never know what you will…
we found an original toyota intake set up and installed, replaced the ebay cold air intake set up, numbers are normal now, no more cel either. First time we have seen a filter cause a lean, seen a lot of rich conditions
You are not missing anything. You replaced the WRONG PARTS, with the right parts, and then the car was fixed. Amazing how that works. :-)
But... but... what about my chrome pipe!!!
Put the pipe down, sir. Say "no" to drugs. :-)
This is exactly why in California an aftermarket cold air intake needs and Executive Order. Changing the way the air enters the throttle body or from the throttle body to the intake runners will have an affect on trims. Your vehicle had enough turbulence to cause an MIL. Most do not cause a code, but can skew trims. For every action, there is a reaction. For better or worse. Rarely is it the same.
Engineers has calibrated for air intake to be at certenanted amount of air volume if you change that ecm does not what to do except add our extract . Keep stock
You are right on Randy, we see this a lot with guys installing performance air intakes. 90% of the time it will skew the AFR. We always suggest a recalibration for the MAF transfer function, most guys look at me like I have three heads (LOL) because its a bolt on and no one else suggests it.
Gord, I do not get into a lot of aftermarket performance parts, so forgive my ignorance. How do you recalibrate the MAF curve when another filter/housing is installed? Do you do it with tuning software?
Jamey, that is correct we are using HP Tuners.
Hi Keith, Good find, FWIW, the air flow sensor and its environment has a calibration transfer function that the ECM uses to infer cylinder air charge. If that known environment is changed, then all bets are off. A week or so ago we had a vehicle in with a terrible idle and what we found was that the air filter had become distorted and was causing a disruption of the airflow around the sensing…
Hi Scott: At least the engine is sealing. :) Guido
That filter brings into question the order of: suck, squeeze, bang, blow! 🧐
Like many of the other respondents mentioned I think it comes down to turbulence created by the filter. I seen this happen with OE filters when partially restricted by snow.