game on

Before I buy an MAF sensor, would appreciate any input for the following problem.

Code 33 is set after the car sits for two days. Disconnect the battery to reset to ecm and all is well with the world, idles fine, power is fine, etc.

I've gone thru the Service manual code 33 diagnostics and keep coming up with, "check connections and if connections are ok, replace the MAF."

I'm getting all the proper voltage readings at the MAF connector and the burnoff module connector to the ecm.

Any thoughts appreciated.

JAKE

Did you visually check the MAF wires to see if one of them is broken? If not, just take off the MAF and look inside at the very thin wires.

You can also try the tap test. With the engine idling, Tapethe bottom of the MAF with the handle of a screwdriver; if the engine stumbles the MAF is bad.

Hope this helps.

Jake

JAKE

I'm told the burn-off relay is behind the dash on the 85. Is that where you looked?

Jake

flylowguy

on my '85 the maf burnoff relay is mounted on the wheel well inner just in front of the battery. The maf power relay is on the firewall just behind the battery. Don't know if that's stock, but there they are.
Says you should replace both relays when you replace a maf.

game on

Visually checked the maf wires and appears none broken.

If maf wires were broken, why would it run ok for 2 days and then not? One would think that if maf wires were broken/open, then it would never run ok.

Thanks for your input. Very frustrating problem to pin down!

JAKE

I must be missing something, because one of our members says the 85 has only one relay and it's behind the dash.

I've got an 86 and it has two, mounted on the firewall behind the battery.

Color me confused.

Jake

game on

According to the GM service manual it is located right of the ecm on the passenger side. I pulled the connector and verified the wiring so I am confident that I had the burn off input to the maf.

The service manual does not reflect relays between the burn off and the maf. However, I do not hear the relay clicking from the dash that happened before this problem showed its ugly face.

Thanks for your input.

JAKE

You've got two, he's got one and other members report that there's only one.

So what did GM do, switch to the two relay setup late in 85?

Jake

game on

Thanks for your input. According to the 85 service manual the realy is located inside the burnoff module. No other relays are shown on the wiring schematic of the service manual.

If the relay was not working, I would not see voltage from the burnoff module after shut down. However, I see the voltage for a couple of seconds at the burnoff connector to the ecm.

I think I will try the maf as the service manual test indicates.

game on

Thanks for your input. I'll check behind the battery for the relay. Would be great if that is the problem because the maf cost $200 plus and the burnoff relay dealership retail cost is $900.00!!

JAKE

". . .why would it run ok for 2 days and then not?" There-in lies the rub. Intermittent problems do things like that. That's the way it tests our perseverance.

Your initial post ended with "Any thoughts. . ." To me that means just that, so I mentioned the things that you hadn't listed as being checked. As to "why", only clues I have is it could be heat or vibration related.

I've seen the tap test in a couple of mag articles and, I believe it's even in the 86 Vette Shop Manual.

So, you got the correct voltages on the burn-off test, but no longer hear the clicking sound that you use to hear. What does that tell you?

Jake

JAKE

WOW! I heard the relay was expensive, but I had no idea it was THAT expensive.

I bought my last MAF at a wrecking yard about three years ago. $50.00 Many 'F' bodies use the same one. If I were you, I'd check for the relay there too

Jake

game on

Jake,

Don't know. Is there a relay inside the maf the caused the clicking or is there a relay located somewhere that the shop manual does not address as flylow suggests?

Thanks for your input.

JAKE

We need to touch base with CFI-EFI, I believe he's up on the 85 setup.

My thought is that if you cannot hear the clicking sound that you use to hear before the problem started, but CANNOT hear it now, then it must be bad even though the voltages check out okay.

If the burn-off relay is working properly, you should be able to actually see the MAF wires glow when you shut down the engine. I've never actually checked mine, but I've read posts where others have checked theirs.

Hopefully guys with 85s or who have watched their burn-off function will post.

But $900, that's outrageous!!!!!!!!!!!!!

Jake

Midnight 85

Don't get a MAF for an 85, they're more expensive. Get one for an 88 for example they're more plentiful and thus cheaper. They will work correctly.

frank j. moran

the burn off module on an 85 is behind the IP (bread box) on the right side. This module is expensive, however it is used on all F bodies in 85 with TPI. Are you sure it's bad, does the wire in the MAF sensor glow when you shut the engine down, if so it doing its job.
frank

game on

I'm not sure of anything. The service manual says replace the maf. I will check for the maf glow as you suggested.

Thanks for your input.

Logging off.

snoopdan

Im jackn' the thread for a minute, but let me get this right - I could turn off the engine, and while looking into the maf, actually see a glow from the wire? Thats cool as sh8T ... how long does the burn off last? Seems like thats the best test to see if your MAF is fubar.. Is that assuming too much?

thnx

snoopdan

rick lambert

Although an 87 is different, my intermittent MAF problem was easily
solved by replacing the MAF burn off relay and power relay (both)
for less than $20. If I were you I'd be locating and replacing your
relay(s).As to location on an 85 I have no idea.

vader86

85 has only one burnoff module inside the passenger dash near the ECM, it does NOT have 2 MAF relays on the firewall behind the battery. GM did not make a change midyear with the 85 either, they didnt do the 2 relays until 86.