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1985 Corvette Burn Off not working for MAF

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Old 04-30-2014, 08:38 PM
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DanielRicany
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Default 1985 Corvette Burn Off not working for MAF

Hey guys I have a 1985 Corvette, and just out of curiosity I wanted to see if my burn off module was working. Turns out it isn't, as it appears.

I'm following this wiring diagram from All Data, and there is supposed to be 12 volts on the Dark Blue wire going to the MAF sensor, circuit number 994, when you shut the car off for like 2 seconds, right?

Well there isn't.

What are the symptoms of a bad burn off module?

Thanks!
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Old 04-30-2014, 08:53 PM
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gerardvg
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If your car is running ok with no codes don't worry about it,
There are plenty of used or new old stock ones on ebay.
The word is out that the 85 corvette burn off module is a one of and the prices have steadily risen over the years, they avarage around $40-$600 Take your pick Every 85 owner needs a spare.

I will post the diagnostic stuff in my shop manual for testing the burn off module, when i get home from work.

http://www.ebay.com/itm/Chevy-Corvette-C4-1985-Maf-Burn-Off-Module-/251518861884?pt=Motors_Car_Truck_Parts_Accessories&hash=item3a8fb1423c&vxp=mtr
http://www.ebay.com/itm/Corvette-Bosch-fuel-injectiom-MAF-Burn-off-relay-1985-14080620-Camaro-Firebird-/161289167466?pt=Motors_Car_Truck_Parts_Accessories&hash=item258d95626a&vxp=mtr
http://www.ebay.com/itm/1985-C4-CORVETTE-TPI-MAF-BURN-OFF-MODULE-14080620-/181382071421?pt=Motors_Car_Truck_Parts_Accessories&fits=Year%3A1985%7CModel%3ACorvette&hash=item2a3b36c47d&vxp=mtr
http://www.ebay.com/itm/Delco-Mass-Air-Flow-Sensor-Module-Camaro-Corvette-Firebird-Trans-Am-1985-NOS-/271423424476?pt=Vintage_Car_Truck_Parts_Accessories&fits=Year%3A1985%7CModel%3ACorvette&hash=item3f3218c7dc&vxp=mtr
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Old 04-30-2014, 11:30 PM
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DanielRicany
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Can that cause an idle surge?
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Old 05-01-2014, 02:23 AM
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xrav22
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Originally Posted by DanielRicany View Post
Can that cause an idle surge?
I can hear a burn sound when I turn it off, sounds like a bug zapper
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Old 05-01-2014, 04:28 AM
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gerardvg
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Ok here you go from my 85 shop manual, the correct test procedures and how the burn off module works. Note the delays before burn off, is very interesting so you can see your burn off module may be perfectly good.

Goes to show how valuable the shop manual is for diagnostic stuff.

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Old 05-01-2014, 04:40 AM
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Cliff Harris
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When I had a bad MAF burnoff relay the symptom was a rough idle. That's caused by the MAF wire getting dirty over time.

The burnoff modules were only used on '85s so they are relatively rare.
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Old 05-01-2014, 06:05 AM
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itsmejimr
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Default MAf

Originally Posted by Cliff Harris View Post
When I had a bad MAF burnoff relay the symptom was a rough idle. That's caused by the MAF wire getting dirty over time.

The burnoff modules were only used on '85s so they are relatively rare.
think you are wrong on the ""85 only" reply. My '89 has 2 burn off sensor relays on the driver's side firewall. I know GM went back and forth with MAF and MAP on the early C-4s. When my went bad it actually coded. About $12.00 ec. to replace.
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Old 05-01-2014, 07:11 AM
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think you are wrong on the ""85 only" reply. My '89 has 2 burn off sensor relays on the driver's side firewall.
I think he means that only '85 used a burn off MODULE, whereas '86-'89 used a burn off RELAY.
'90 & '91 L98s were SD and so had no MAF.
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Old 05-01-2014, 12:14 PM
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DanielRicany
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Thanks everybody for the help. It appears the burn off module is not functioning properly.

I followed the diagram and it told me that I have either a bad module or bad continuity, I tested continuity, it checked out okay, so now it says I have a bad module.

Before I replace the module I wanted to test the harness and make sure that I was getting the proper voltages and grounds where I should be. I do get them but on the pink/black wire, I get like an intermittent voltage signal. I posted another thread on that, and if it turns out to be a bad connection or perfectly normal, then I will decide whether or not to replace it.

Thank you everybody!
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Old 05-02-2014, 01:35 AM
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Cliff Harris
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Originally Posted by DanielRicany View Post
Before I replace the module I wanted to test the harness and make sure that I was getting the proper voltages and grounds where I should be. I do get them but on the pink/black wire, I get like an intermittent voltage signal.
The pink/black wires only have 12 volts on them when the ignition is on. They are labelled "HOT IN RUN" in the wiring diagrams.

Hopefully that explains your intermittent problem...
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Old 05-02-2014, 02:48 AM
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Originally Posted by gerardvg View Post
...every 85 owner needs a spare.
- I have a spare, and I don't even own an 85 (anymore) - - my son owns my old 85. as long as the car is in the family, the part remains in the parts stash!
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