Code 31

[Anomili]

Thus, it begins. About two months ago my car developed a problem whereby it would stall following periods of time with high load on the engine. Later it began to stall when I depressed the clutch at, say, a stop light. One day the car just began to throw a constant code 31. I figured that it was a bad AFM so I replaced it. After a month of waiting my new afm FINALLY arrived today. I installed it and the car ran fine. Until I hit the gas. Suddenly when I let off the whole car decided it hated life. It began to idle very very rough with the rpm barely enough to keep the engine turning. Then re-appeared the dreaded code 31. Now I am at a loss. I turned the idle screw until it was almost out and the car would still only idle at a max rpm of 1000 and still very roughly. I have a vacuum of around 15 psi and my blow off valve is securely on. The only problem I can think of is that there is some kind of short between the afm and the ecu. Other then that, the only part that may be iffy is my o2 sensor, but I don't think that has much effect on a code 31. Also... Originally the car threw code 24, but after I cleared it and restarted the car it showed only 31. I repeated this 3 times and each time it showed 31 (and I did clear the codes after each try.) The codes came back pretty much instantly after I turned the car on.

My car is completely FUBAR and I really appreciate any help you guys can give. I am just praying right now that I didn't destroy my new afm (still have to check resistance.)

 

[Anomili]

Update: I just checked the resistivity of my new afm and it is giving almost identical readings to my dead afm. So there are two possibilities:

a) The problem is within the electrical system, but my multimeter is wrong (it's a cheap one) and the AFM's both work.
b) There is a problem with the electrical system and the AFM's were destroyed.

I still have no idea if my predictions about the short curcuit are valid. And I am really at a loss.

Again, any help is appreciated.

 

[Anomili]

Wow, I guess this problem isn't really all that common? Someone has to know whats going on...

 

[aye mate]

I also was getting a code 31 but a replacement AFM fixed my problem. I wouldn't know what to tell you??? except go MAFT... haha I am fixing on going with the maft set up soon to get rid the head-ache that is the Kaarman Vortex do hicky. Hope you find the problem!
EDIT: did you test the wire harness side?

 

[Anomili]

Thanks, still working on it. I think I shall tear apart my harness tomorrow and check for shorts.

 

[Anomili]

Update: I spent 9 and a half hours today out in the sun working on the car. I replaced all my plugs and cleared as much oil out of the area as possible. After reassembly the car ran beautifully, for about 5 minutes. My friend and I then decided to wire in my new s-afc 1 and avc-r. The s-afc I installed smoothly and showed that my engine was in fact alive (even though it was not recording any air flow .) The avc-r, on the other hand, which I had bought from my friend, arrived broken and would only turn on when any button was held down (it would turn off when you let go of the button.) We then plugged it into his mk4 and it didn't work in his car either (he had another working one in his car.) We ripped out the harness and low and behold... The entire electrical system took a massive dump and decided to cease all power supplies to the ECU and s-afc. Of course, we realized this problem AFTER we had removed the s-afc and its harness thinking that it too had been broken.

Anyways, I still can't get the car to start now, nor can I get any power to the ecu. I checked the main fuse box to find it in perfect order. I also checked all the wires we cut and spliced to make sure there were not any shorts and that they ran to the correct locations. My only hope now is that one of the fuses in the smaller compartment nearby blew. Otherwise I am once again at a loss.

Edit: It could have been a relay... not very sure about that though...

 

[Anomili]

Just so people know... I am not intentionally talking to myself, I just want to make sure that someone with a similar problem NEVER has to go through what I am going through. Hopefully by the time I have sorted this out this thread will be able to help someone else out in the future.

 

[Anomili]

And I feel that given my bad luck recently, I deserve to be a post whore... at least for tonight.

 

[Boostedstr8six]

It probably wasn't the best idea to install your piggy-backs before you solved your code 31. That aside, have you hit the afm harness with your multimeter? You could have a broken connection there at the plug. Also, what does your exhaust look like? I'd expect sooty emissions from an afm problem.

 

[Anomili]

I checked out both my afm's with a radio shack multimeter. I am going to go grab a better meter tomorrow at Canadian Tire, until then I haven't checked the harness itself. I did however check the ecu harness and that was what showed no power. And following the installation of the plugs all the symptoms went away, as did the check engine light. I had no idea that there was a problem with the afm until the s-afc told me that there was no air flow into the engine while it was on. Regardless of the lack of reading... the car was idling fine.

P.S. My old spark plugs were oil doused and pitch black with soot.

 

[Boostedstr8six]

I really do think it's an afm-ecu connectivity problem. That's my best guess from what you've stated.

How does it behave when you drive it? If my guess is accurate then driving would be very difficult. Idling is totally different. It's just tough to diagnose these kind of things without being there and my knowledge is somewhat limited. :dunno:

 

[Anomili]

This is the confusing part. When we drove it yesterday, before the new plugs and the electronics, the car drove normally, except for when you let of the gas. At say a stop light, the rpm would drop and idle roughly, sometimes struggling to survive. It also backfired once. It did not however, show the signs of a faulty afm as the car could in fact move. I think that the major idling problem was fixed when I replaced my plugs which were really freakin old. We didn't drive it after I installed the new plugs, but the car sat in the driveway at 100% constant idle... NO fluctuations. Shortly after, the power to the ecu disappeared. I am hazarding a guess that at some point two wires shorted out before we disconnected the battery, thus blowing a fuse. To add yet another twist to this story, for the short time that the s-afc was working, it showed 0% air flow ?!? But the car was idling perfect!

 

[Anomili]

Update: I got the car running again. Turns out that the starting problem was a blow ignition fuse. The car now stalls whenever the gas pedal is released. As well, iIt will idle normally for approx. 2 minutes at startup before stalling. Now I checked the resistance for my old AFM and my new one that I just got... both were way off. When I needed 5-K ohms I got 5.6 M ohms when I needed 10-15 I got 170. This makes me wonder if there it is possible for the electrical system to break an afm. Personally I think the one I ordered arrived broken, but I can't be sure. I just don't see how the harness could break an afm. Anyone know definitively?

 

[Anomili]

Final Update: It's late and I've been working/driving the car all day. The final problem was a missing ground wire used to ground the coil packs. I LOVE ELECTRICAL PROBLEMS. On the up side... Greddy Catch Can, S-AFC I, AVC-R and Champion spark plugs all installed...woot

 

[Yawgmoth]

This is strange becuase I am having the same problem, I might reground the coilpacks...

I was thinking as you did, that the wiring was causing a short or something in between the afm and ecu, or that my ecu was bad becuase I just bought a brand new wiring harnerss from toyota...wait a minute...what am I doing typing? I'm going to go ground those wires

 

[Idealsupra]

for the record... my coilpack ground wire has NEVER been attached...my car ran fine....a few others around here the same way

 

[Anomili]

Really? Well we did a lot in one day, we installed the Catch can, avc-r, and s-afc. But after I grounded the coil packs the car idled normally again. I can't really explain it, which is really why I love electrical problems. The car runs now, but who knows what it was that ultimately got it going again.

 

[Yawgmoth]

yeah my coilpacks are grounded, nothing changed...bummer

 

[Anomili]

Yeah, sorry that I let this thread die for soo long. I recently came into a spare 7m which I have been tearing apart in all my spare time. The car drove normally for a while then it all went to hell again. Now the car runs the same regardless of whether or not the afm is connected. I would say, get a new afm, but I have tried 3. 2 of these worked on other cars and 1 I saw working on a running car. However, they all gave the same erroneous numbers when tested with a multimeter and none of them worked on my car. I am now led to believe that it is in fact the ecu that is broken. That is the only option aside from there being a short somewhere in the harness. I am really stumped and frustrated with this, but I think that I will replace the ecu before complaining more.

 

[montoya_mk3]

This exact problem is happening to me right now....EXACTLY!!!!!!!!!

Have you found anything else out?