Car dies at idle

[Ryncub]

My 87 Supra Turbo won't idle. It'll run fine in gear and even at idle speeds as long as I keep my foot on the gas, but if I let off the gas with it in neutral or with the clutch down, it dies.
Any help? I was thinking it might be something with the pollution control stuff... filters, hoses, switches? I'm going to go poke around, but I think this is going to be a wild goose chase.

(New head gasket, valves 9 months ago)

Thanks,
Ryan

[TcmaBoy]

Look for a vac leak.

[Peter]

my buddy had idle problems it was AFM
my moms car had the same problm as long as the reves are up its good , and when u levt go it just stalls....


i found out the throddle body was dirt and i cleaned it with intakemaifold cleaner...works good to.....

[Jeeves]

The options above are all things I'd check. Take a multimeter and confirm that the AFM passes.

[CryoSlash]

could even be dirty spark plugs. you wont know anything till you try.

[Ryncub]

I've measured the AFM with a digital volt meter and came up with wrong results because apparently an analog meter is required (I do not have an analog meter).
Then I ran the supra self diagnostics through the onboard computer... it first came up with code 11 (ECU +B), everything checked out OK. I reset the diagnostics, re-ran the test, and it came up with code 31 ("AFM Signal, open or short circuit in AFM signal").
So I checked ECU terminals VC to E2 and came up with 5 volts. All other tests seemed to check out OK. Since I can't think of any way it's coming up with 5 volts aside from the actual AFM being bad, I'm leaning towards that as the culprit.
Would anyone agree or have any other ideas after reading all of this?
What should an AFM cost and what is the availablity? Would a dealer stock this, order it, or am I better off ebaying it?

Thanks.

Ryan

[Jeeves]

Dealer will run you > $400 IIRC, your best bet is looking on ebay.com, junkyards or supraforums.com

[5mg_sup]

it might be your booster

[Jeeves]

I think you meant to say "brake booster."