Mass Airflow Sensor
Thread Starter
Instructor
Joined: Nov 2008
Posts: 170
Likes: 0
From: Odessa Tx
Mass Airflow Sensor
So I got my 85 finally fired up today and broke the motor in. I set the timing and as I throttle up it is good until I get to where the throttle is open all the way. After about opening half way it began to be sluggish. I unplugged the mass airflow sensor and it ran much better on the top end. I am going to buy a new sesor. Is this probably the main problem?
Corvette Enthusiast
Joined: Oct 2007
Posts: 6,791
Likes: 2,697
From: So. Cal.
2025 C7 of the Year Finalist- Unmodified
2024 C7 of the Year Finalist - Unmodified
2023 C7 of the Year Finalist - Unmodified
maybe
doesnt 85 not have separate burn off relays for the maf? Controlled by ecm ?
Might be maf.
Might be maf.
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 8
From: Tampa Florida
Thread Starter
Instructor
Joined: Nov 2008
Posts: 170
Likes: 0
From: Odessa Tx
It should have that relay... I will try that tomorrow. Is there any way to test the MAFS? I know that I cleaned it out and the wire that is inside is in tact. I did not touch it with anything.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 8
From: Tampa Florida
Race Director
Joined: Aug 2000
Posts: 14,130
Likes: 7
Cruise-In II Veteran
The 85 had a MAF burn off module.Not the relays like the 86 and later cars had.Its located inside the dash.
Are you getting a code?Engine light?
Also,if you added a larger Throttle body or adjusted the TPS and minim air incorrectly,it can cause a similar problem.I only ask this is because you just started it back up,and I have no idea if you did an adjustment or not.
An incorrected adjusted TPS with the min air speed off can cause a code 33 MAF problem and fall flat on its face.
Are you getting a code?Engine light?
Also,if you added a larger Throttle body or adjusted the TPS and minim air incorrectly,it can cause a similar problem.I only ask this is because you just started it back up,and I have no idea if you did an adjustment or not.
An incorrected adjusted TPS with the min air speed off can cause a code 33 MAF problem and fall flat on its face.
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 8
From: Tampa Florida
The 85 had a MAF burn off module.Not the relays like the 86 and later cars had.Its located inside the dash.
Are you getting a code?Engine light?
Also,if you added a larger Throttle body or adjusted the TPS and minim air incorrectly,it can cause a similar problem.I only ask this is because you just started it back up,and I have no idea if you did an adjustment or not.
An incorrected adjusted TPS with the min air speed off can cause a code 33 MAF problem and fall flat on its face.
Are you getting a code?Engine light?
Also,if you added a larger Throttle body or adjusted the TPS and minim air incorrectly,it can cause a similar problem.I only ask this is because you just started it back up,and I have no idea if you did an adjustment or not.
An incorrected adjusted TPS with the min air speed off can cause a code 33 MAF problem and fall flat on its face.
I agree with checking for a correct TPS voltage setting.
Pro
Joined: Dec 2008
Posts: 658
Likes: 0
From: Lubbock for now, headed for Oklahoma
your sooooo right! He may not even be falling in the parameters for a code set. I don't know what they were but the parameters for the older computers where much wider than they are for the newer.
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
In my case my '85 had a bad burnoff module and never threw a code. Also, since he cleaned the maf and it didn't help it most likely eliminates the module as a problem. I would do the settings as suggested before buying any parts.
Pro
Joined: Dec 2008
Posts: 658
Likes: 0
From: Lubbock for now, headed for Oklahoma
UH OH! well that may change a few things. With everything that you have already given us and that I am kinda wondering if you have an exhaust restriction.
Catalytic converters and mufflers alike can clog up enough to cause these issues. Do you have a vacuum gauge?
Catalytic converters and mufflers alike can clog up enough to cause these issues. Do you have a vacuum gauge?
Pro
Joined: Dec 2008
Posts: 658
Likes: 0
From: Lubbock for now, headed for Oklahoma
Well that rules that out for sure. Okay well it could still have a bad MAF really to test them you need an oscilloscope. Could be a bad MAP IF your car has one. Or a weak EGR valve spring.
A dirty way to test for EGR is to just unbolt it, put a dime over the hole and bolt it back down on the dime, you can also use a cut piece of an aluminum can.
If you use a dime don't torque it down real tight as the dime is just a close fit but a little big. You can break your EGR.
A dirty way to test for EGR is to just unbolt it, put a dime over the hole and bolt it back down on the dime, you can also use a cut piece of an aluminum can.
If you use a dime don't torque it down real tight as the dime is just a close fit but a little big. You can break your EGR.