'85 MAF burnoff question.
06-10-2003, 07:28 PM
#1
Le Mans Master
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'85 MAF burnoff question.
I am trying to test my MAF burnoff function on the vette, and am not sure if I remember it right.
Run the engine, turn off the ignition/take keys out, and within 20 or 30 seconds, the MAF wire should glow red as it is burning off the dirt particles off it.. I am nto getting any codes or bad MAf/Burnoff module symptoms, but I tried 2 MAF's and neither seem to glow the wires inside ..
Thanks in advance
Run the engine, turn off the ignition/take keys out, and within 20 or 30 seconds, the MAF wire should glow red as it is burning off the dirt particles off it.. I am nto getting any codes or bad MAf/Burnoff module symptoms, but I tried 2 MAF's and neither seem to glow the wires inside ..
Thanks in advance
06-10-2003, 08:15 PM
#2
Team Owner
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Location: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
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Re: '85 MAF burnoff question. (MrNuke)
:lurk: Hmm... This is supposed to occur everytime you shut the car off to keep the maf coils clean?
TTT
TTT
06-11-2003, 11:58 AM
#4
Life's Short. Drive Hard.
Re: '85 MAF burnoff question. (MrNuke)
Because of their location, MAFs are in a good place for contamination. Like bugs on your teeth after a long motorcycle ride, residue builds up on the MAF wires and the PCM must remove it. The burnoff cycle will usually happen after the vehicle has been run in closed loop and then shut down. When it does happen, you will see the wires inside the MAF heating to about 1,000 degrees Fahrenheit for a few seconds after shutdown. At the same time, the PCM monitors the signal line to see if a feedback voltage was induced from the MAF to find out if the burnoff cycle happened. I think your best bet is to energize the burnoff relay by grounding it at the PCM after unplugging the MAF. If you leave it plugged in for more than a few seconds, your MAF will be so clean it smokes! Check for power at the MAF. Both the power wire and the burnoff wire should have power. If one doesn't light, you have a relay problem, a wiring problem, or a meter problem. Check both the power relay and burnoff relay. If they light, tap the relays lightly with a small screwdriver. Did the light flicker or the meter jump? Check the connections and wiring. If this checks out OK, you have a few options. The relays should be updated. There have been voltage drop problems through the relays that are only evident during the burnoff cycle. You can also try a road test, watching the voltage at the PCM on the burnoff wire. The voltage should drop briefly from 12 volts to 0 volts after the car is shut off. At the same time, watch the MAF wires - they should glow briefly. If this happens, the PCM did its job. Good luck.
06-11-2003, 01:09 PM
#5
Le Mans Master
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'85 MAF burnoff question.
I've done the knock on the MAF test, no difference. I am not getting any issues or Check Engine Light, but the ram air is such a pain to remove when the car is running to see inside the MAF, I might just save this for this weekend..
Thanks for all the replies. :cheers:
Thanks for all the replies. :cheers:
06-11-2003, 02:07 PM
#6
- 1986 Original Owner -
Re: '85 MAF burnoff question. (sgt538)
Because of their location, MAFs are in a good place for contamination. Like bugs on your teeth after a long motorcycle ride, residue builds up on the MAF wires and the PCM must remove it. The burnoff cycle will usually happen after the vehicle has been run in closed loop and then shut down. When it does happen, you will see the wires inside the MAF heating to about 1,000 degrees Fahrenheit for a few seconds after shutdown. At the same time, the PCM monitors the signal line to see if a feedback voltage was induced from the MAF to find out if the burnoff cycle happened. I think your best bet is to energize the burnoff relay by grounding it at the PCM after unplugging the MAF. If you leave it plugged in for more than a few seconds, your MAF will be so clean it smokes! Check for power at the MAF. Both the power wire and the burnoff wire should have power. If one doesn't light, you have a relay problem, a wiring problem, or a meter problem. Check both the power relay and burnoff relay. If they light, tap the relays lightly with a small screwdriver. Did the light flicker or the meter jump? Check the connections and wiring. If this checks out OK, you have a few options. The relays should be updated. There have been voltage drop problems through the relays that are only evident during the burnoff cycle. You can also try a road test, watching the voltage at the PCM on the burnoff wire. The voltage should drop briefly from 12 volts to 0 volts after the car is shut off. At the same time, watch the MAF wires - they should glow briefly. If this happens, the PCM did its job. Good luck.
06-11-2003, 02:40 PM
#7
Burning Brakes
Re: '85 MAF burnoff question. (MrNuke)
I had problems with the MAF sensor on my '89 Camaro TPI engine which is very similar to the corvette. The engine was hesitating and not running smoothly. It ran better with the MAF disconnected. I had no error messages and the MAF showed a smooth variation with airflow. Furthermore, I was getting voltage at the MAF for burnoff. However, it wasn't heating and cleaning the wire. I replaced the MAF and the problem went away.
