Skip the auto shop - Our mechanics make house calls

Q: Question About changing the Diameter of MAF housing

asked by on

I'll try to keep this as simple as possible.

I have an aftermarket intake with a MAF housing SMALLER than stock.

After realizing that the intake was causing me to run rich, I decided to experiment with ways to "offset" the rich condition.

I drilled a hole in the aftermarket intake AFTER the MAF sensor hoping that this would create a vacuum leak and cause a more "Lean" Condition.

After taking a bunch of data logs, I discovered that having an open valve AFTER the MAF housing (Air being Unaccounted for by the ECU) actually caused me to run slightly MORE RICH.

Please explain how this can happen.
My car has an automatic transmission.

A: Hi there. The oxygen sensor still detects r...

Hi there. The oxygen sensor still detects rich/lean, regardless of how the mixture is calculated, and sends "lean it down" or ’richen it up" signals to engine management. If engine management is out of range on the combination of signals it knows how to operate with, it could be too rich, or worse yet, could default to an "open loop" mode, where it essentially gives up on rich/lean management (such as during engine warm-up where the engine is, by design, running pretty rich). Working with modified OEM systems that are not really adjustable is hard, and can easily produce the results, and challenges you are experiencing.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Low rpm idle

Since you had the battery disconnected the computer needs to relearn the idle again. I would recommend having the throttle body cleaned and then the throttle relearn process done so the idle can stabilize and be relearned by the computer....

Q: P0705 - 2007 Scion tC

Hello and thanks for contacting YourMechanic. The code P0705 means the transmission range sensor circuit has a fault. This is usually caused by the sensor on the transmission failing. After installing the remote start switch, if you did not hook...

Q: Why can't i fix O2 sensor problem

In many circumstances, the O2 sensors are not the only culprit of a lean fuel curve. In many cases, a clogged fuel injector nozzle can also trigger the most common OBD-II error code (P-2191) that indicates a lean condition exists....

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...