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86 code 33 maf power

N

never2nd

Guest
86 throwing out 33 code. I followed the factory diagnostic chart and got nowhere. One thing I can't seem to find out is should there be power to the maf when ignition is off?
I pull the maf harness off and probe with test light and the light comes on when I probe the two sockets on one end (power and burn off signal) of the harness. Ignition off. Why would the maf need power, or burn off signal, when ignition off?
I've done the relay thing too many times to count, so many that I'm not certain either of them, though new, are good.
Any help much appreciated.
Thanks!
 

warp8

Well-known member
Joined
Jun 5, 2006
Messages
95
Location
Florida
The only power to the MAFS with the ignition off is through the burn off circuit. This heats the wire to clean it. Take it slowly through the chart and it will lead you to the problem.
 

Mad-Mic

Gone but not forgotten
Joined
Feb 12, 2002
Messages
1,853
Location
Annapolis Maryland
Corvette
1987 Redskin Red Coupe
behind your batter is 2 circuits

DSC00552-1.jpg


change these out. i think they are 5 or so bucks each.
 
N

never2nd

Guest
I did that

Thanks for the response.
Both relays are new, as is the MAF. I've checked every wire on both relay harnesses and on the MAF harness. Start it up, it runs for 5 seconds or so then throws code 33.
The car is somewhat drivable, it hesitates on acceleration, and idles like it is about ready to die. I don't know what to do next.
 

warp8

Well-known member
Joined
Jun 5, 2006
Messages
95
Location
Florida
Thanks for the response.
Both relays are new, as is the MAF. I've checked every wire on both relay harnesses and on the MAF harness. Start it up, it runs for 5 seconds or so then throws code 33.
The car is somewhat drivable, it hesitates on acceleration, and idles like it is about ready to die. I don't know what to do next.


Did you run the trouble shooting chart in the FSM? It will tell why the code is thrown. Sounds like the MAF itself. You stated that the chart led you nowhere. If you follow it carefully, it will tell you where the problem is.
 
N

never2nd

Guest
update

Last night I hooked up a volt meter to the maf sensor purple wire to check for 12 volt power. As soon as I hooked the volt meter to the wire, I showed 12 volts to the sensor, with the ignition off.
I started the car and the meter started reading over 14 volts, as if I were reading it straight from the alternator. ?????
 

Agent 86

Well-known member
Joined
Mar 11, 2005
Messages
144
Location
Summerland, B.C. Canada
Corvette
86 4+3 Coupe-Yellow
Last night I hooked up a volt meter to the maf sensor purple wire to check for 12 volt power. As soon as I hooked the volt meter to the wire, I showed 12 volts to the sensor, with the ignition off.
I started the car and the meter started reading over 14 volts, as if I were reading it straight from the alternator. ?????
Normal, all your 12 volt circuits will show an increase in voltage with motor running. :beer
 
N

never2nd

Guest
ignition off

Why would the sensor need 12 volts with ignition off? Battery will drain in a few hours.
 

warp8

Well-known member
Joined
Jun 5, 2006
Messages
95
Location
Florida
Why would the sensor need 12 volts with ignition off? Battery will drain in a few hours.


Last Try!! Power to the MAF via the Purple wire 993 at terminal E comes from one place -through the MAF Power Relay Terminal A. I don't think you are running the Code 33 chart right. The MAF should not have power at terminal E after the Burn Off Relay has done it's thing. The burn off circuit activates for a short time after the ignition is turned off. There should not then be any power to the relay. Run the chart and you will find the problem. Randomly probing wires tells you nothing!
 
N

never2nd

Guest
Last time?

I've ran the chart four times. How do you think I replaced the relays....because of the chart.
What do you mean last time?
I have power to the sensor WITH THE IGNITION OFF, both the burn off signal, and 12 volt power. Doesn't say anything in the FSM chart about that.
The last box on chart says replace the b.o. relay. Done that. Twice.
 

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