Mas burnoff
Le Mans Master
Joined: Sep 2006
Posts: 6,050
Likes: 147
From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
Mass air burnoff module
In 86, they incorporated the controls for the mass air hot wire burnoff into the computer (ECM).
since your year was the first TPI, they had a stand alone control for the burnoff cycle.
the mass air sensor has a sensing wire yhat is heated to a specific temperature.
As air entering it cools it off, there is a calibrated module that supplies it with a voltage to keep it as hot as it should be.
that voltage translates to a specific amount of air.
that equation is part of your fuel ratio computation.
the hot wire picks up dirt such as what’s under your refrigerator. They use that module to send a higher amperage through the hotwire to burn off contaminants that disturb the airflow and mixture computation after u shut off the key. The current lasts about 6-8 seconds. There is a burnoff relay that actually puts the power to the mass air sensor controlled by that little box
since your year was the first TPI, they had a stand alone control for the burnoff cycle.
the mass air sensor has a sensing wire yhat is heated to a specific temperature.
As air entering it cools it off, there is a calibrated module that supplies it with a voltage to keep it as hot as it should be.
that voltage translates to a specific amount of air.
that equation is part of your fuel ratio computation.
the hot wire picks up dirt such as what’s under your refrigerator. They use that module to send a higher amperage through the hotwire to burn off contaminants that disturb the airflow and mixture computation after u shut off the key. The current lasts about 6-8 seconds. There is a burnoff relay that actually puts the power to the mass air sensor controlled by that little box
Le Mans Master
Joined: Sep 2006
Posts: 6,050
Likes: 147
From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
Mass air
I don’t think the mass air sensor is relevant to the burnoff cycle.
relevancy is the resistance and thickness of the Hotwire to take the amps. Since later models have a burnoff cycle, no harm, no foul.
you need a box like that installed to clean the hotwire because of your ecm.
it needs the stand alone box to accomplish the burnoff.
if I remember correctly, it is on the right side of the car near the engine computer.
you might just check to see that there is one, and it’s plugged in.
relevancy is the resistance and thickness of the Hotwire to take the amps. Since later models have a burnoff cycle, no harm, no foul.
you need a box like that installed to clean the hotwire because of your ecm.
it needs the stand alone box to accomplish the burnoff.
if I remember correctly, it is on the right side of the car near the engine computer.
you might just check to see that there is one, and it’s plugged in.
Last edited by coupeguy2001; Nov 16, 2021 at 09:41 PM.
Instructor
Joined: Oct 2018
Posts: 225
Likes: 81
From: Vancouver, WA
I have an 85 Corvette and had to replace my MAF Burnoff Module and and MAF sensor. Both are 1985 only parts (also used in 85 Camaros and 85 Firebirds).I bought a rebuilt OEM MAF sensor from Blue Streak Electronics. I had to go to a salvage yard for a used MAF Burnoff Module. They quit making the Burnoff Module 20+ years ago.
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Safety Car
Joined: May 2001
Posts: 4,735
Likes: 1,635
From: Fairfax Virginia
I have a 1988 C4 Coupe and it has the newer style M*** Air Flow and uses the Burn Off cycles to keep the MAF operating correctly.
On my C4 it uses two separate relays, One controls the Power to the MAF and the second controls the Burn-Off Function. I see people buy a new MAF and then have the bad relay hurt the new MAF. Always replace the three parts together, the MAF and the two relays. This is how the system works on later models, maybe an upgrade or conversion might help? On the later models the Relays testers can identify problems since it is a basic relay.
If you want to "solve the problem" it might be easier to switch to a M*** Air Pressure (MAP) system. Due to rising costs people have done that as opposed to fixing the MAF systems.
On my C4 it uses two separate relays, One controls the Power to the MAF and the second controls the Burn-Off Function. I see people buy a new MAF and then have the bad relay hurt the new MAF. Always replace the three parts together, the MAF and the two relays. This is how the system works on later models, maybe an upgrade or conversion might help? On the later models the Relays testers can identify problems since it is a basic relay.
If you want to "solve the problem" it might be easier to switch to a M*** Air Pressure (MAP) system. Due to rising costs people have done that as opposed to fixing the MAF systems.