Code 31, 1987 Turbo 65k miles, unmodified.

bestsupraever

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#1
Hi Guys, need your expert help again, with a new problem or perhaps an extension of the old Hard Start When Hot Problem which I believed I solved.
So I am driving along, car is running great, starting right up, hot or cold, idle right around 600, smooth as silk. I come off the highway where I was cruising along about 65 mph for about 15 minutes, get to a stop light, and there is a smell of gasoline, just like what you smell when an old 60's car goes by, running rich. And the supra wants to stall, idle is going up and down from about 500 to 900, and I have to give it a little gas to keep it running. Also I notice the cel is intermittently on and off. On at idle up to about 1000 rpm's and then off above that. And it is obviously running rich. So I make it home, giving it a bit of throttle at stop lights. Check the codes at home, and there is code 31. So I check the manual, and it is pointing to the AFM, open or short. or possible the wiring, or the ecu. So I take a close look at the AFM, and notice a chip on one corner. I check the resistance, as per the manual, and at about 100 degrees, it is reading 1.600, which seems about right. So any suggestions how to proceed. If I need another AFM, which is obviously no longer available from toyota, I guess my options are a yard, or Ebay, or a Cardone Reman. either of which is a risk to get one that is not good, or used up to the point that it won't last very long.
Thanks for any ideas you guys may have. Sorry for the blurry picts, all I am working with is a 10 yr old blackberry.
Semper Fi
IMG00471-20160212-2013.jpg IMG00470-20160212-2013.jpg IMG00472-20160212-2014.jpg
 

Piratetip

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#2
Resistance between E2 & THA was what? 1.600 or 1,600 Ω ?

I wouldn't trust a reman karman vortex AFM, but that's just me. YMMV
My 87' original AFM has 170k on it with no issues yet, I would just get a used one.
Its a gamble getting used of course, if someone ruined one with MAF cleaner or something stupid.
Get one from a reputable member here or another forum.

Maybe someone will chime in if they bought a reman AFM.
 

bestsupraever

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#3
Hi, thanks for the response. i measured the resistances this morning at about 75 degrees.
Tha - e1 = 2.24 in range
Ks to E1 = 0 no resistance
E1 to Ks = 12.51 in range
Vc to E1 = 9.24 slightly low
E1 to Vc =86.1 should be 5-10
From these values I believe that I can conclude that the afm is wasted.
Your opinions are highly valued.
Semper Fi
 

jetjock

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#5
2006? Geez, I really should move on. The car is long gone.

Yeah, THA is meaningless and unrelated to code 31. Resistance checks of the KS stuff are about as useful. Use the freq function of a good meter although a scope is better. There was some earlier talk about the OP cleaning the AFM. If he did that it's toast...
 

jetjock

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#7
From his other thread:

"...My next endeavor while I am waiting for the switch, will be to take the AFM out and clean it with CRC Mass Airflow Cleaner, as I have seen some cases where a dirty AFM could cause a heat soaked engine to hard start. I know to be super careful to not touch the wires in it at all...."

He was warned but I dunno if he saw it in time. As I said in that thread when one doesn't understand how something works (note the reference to a hot wire mass flow sensor) fixing it can a tough nut to crack. He also seems a bit Dunning-Kruger. That isn't going to help any. Gets credit for trying though.
 

bestsupraever

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#8
Hi guys, thanks for the replies. I was going to clean it, but i did see the warning about the consequences, and did not do it. I think it has been a problem brewing for a while, and finally came to light. I only just got the car back in oct, and don,t know what may have been done before me. There has been some small idle issues sporadically, and then the hot start issue, which, with you guys advice I believe I did fix. And now this. After the code, i did pull the afm out to test it, before posting. It has an oily residue on it, not real thick, but more than just dust. I don,t know if that may have hastened the problem, but I know it shouldn't have been there. I will now pull the entire intake tube and filter off to check the dirt factor, and see what filter is in there. Clean it, and put a dry filter in. I have ordered a new/used afm from a reputable seller, and it should be here by wed. I will ohm it, and pop it in and post my results. Btw jetjock, your post on the afm was very helpful. Another post i found that was very explanatory is, http://oldschool.supracentral.com/htm/repair.htm Thanks for the advice, Semper Fi
 

bestsupraever

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#9
Re: Code 31, 1987 Turbo 65k miles, unmodified.--Fixed

Hi Guys, I received the new/used AFM today, (used from ebay not remanned thanks Piratetip). Before I installed it I did the same resistance measurements on it as the original afm that I removed. The only major difference was the E1 to Ks measurement. On the original it measured 12.51 ohms, which should be in range. On the new/used one that I received the E1 to Ks measures 19.50, which according to the manual is actually out of range. So I did the only reasonable thing, and installed it. I then cleared the codes, and pulled codes to make sure they were cleared. I then went out for a drive, the car started right up. I drove for about an hour and a half, making a few stops on the way, shut down, went in store came back out in a 10 to 20 minutes, Drove at street speeds, and highway speeds up to 75 mph, ac on, ac off. The car ran great, smooth as silk, started right up each time, idled right around 650 in drive, no stumbling, plenty of power on tap, no complaints, no cel. Pulled codes at the end of the drive, and no codes. So at this point I will have to conclude that this problem was the afm, and the new/used one solved it.
Luck to all. Semper Fi.