Tips & Tricks

Mass Airflow: Repairing Tuned Port Inductions

Basics for fixing common problems with Tuned Port Induction

By Cam Benty

Photography: Cam Benty



When the Tuned Port fuel-injection system arrived in 1985, it was a significant improvement on the throttle-body systems that came before. Much cooler looking and with more power potential, the Tuned Port Injection (TPI) system used a mass airflow sensor (MAF) to determine fuel/air mixture.

The Tuned Port MAF sensor is a sensitive piece of equipment that incorporates a thin piece of wire that reads air intake and reports to the computer the current air conditions. If the wire is damaged in any way, the engine will not run properly, hunting for a rich or lean mixture to keep the engine operating. Regardless, the engine will not meet performance or pollution requirements.

Our '86 Corvette was running poorly. A diagnostic check netted a Mass Airflow Meter error code (number 34). In addition, several of the air-cleaner pieces were broken, including the clips attaching the MAF sensor to the air intake, the air-cleaner element box screw mounts, and the air snorkel from the MAF to the throttle body had picked up a hole. Any or all of these problems can cause the MAF sensor to misinterpret the data from the computer.

Parts List

Zip Products: Modified Mass Air Flow Sensor, part number EH-478; Air Filter Housing, part number AC-134; Air Intake Duct, part number EH-459

K&N: Air Filter Element, part number 33-2014

One call to Zip Products fixed all that. In addition, we improved the flow of the system with a K&N air filter and a Modified Mass Air Flow Sensor. The installation took about five minutes, and a recheck of the system netted an all-clear by the computer. This is truly a simple fix and one that any novice mechanic can complete. If you can change an air-filter element, you can complete this operation.

The Modified Mass Air Flow Sensor is an excellent changeover to any TPI system. The Modified unit allows more air to flow through the sensor into the engine. As any engine builder knows, the more air your engine ingests, the more potential power you can generate. Knowing that the intake system of these cars is already somewhat restricted by the underhood configuration of the engine compartment, anything that increases airflow is a good thing. If you're already changing the MAF sensor, this swap is a good idea.

Follow along as we repair and improve the intake system on our '86 Corvette. It's easy.



The basic layout of the intake system on our TPI '86 Corvette. Disconnect the battery when performing any engine work.


A check of the diagnostic system on our Corvette resulted in a faulty MAF-sensor readout.


Our air-filter housing had broken tabs at the point where it was to connect with the MAF sensor. The new housing was a dramatic improvement.


The air-intake duct had a hole, allowing air and debris into the engine behind the MAF sensor and air-filter element. Bad news.






(above & right) The air-cleaner box tab mount (arrow) was broken off, allowing debris into the intake system behind the air-cleaner element.

(above & below left) The new Modified Mass Air Flow Sensor looks like the stock unit on the outside and mounts in the factory location. When removing the original MAF sensor, be sure to disconnect the electrical connector.

The one electrical connector that leads to the MAF sensor should be cleaned with electrical contact spray, allowed to dry, then reconnected.