Car runs like crap. Code 31. Cant find problem.

[chevyguyjoe]

Here is the back story. Been running 12 psi. Stock everything except: exhaust after the elbow, air filter, head gasket. Been running great, except for hard starting an a cold start, below 50 degrees Fahrenheit. Had that problem since i bought it. Blew a power steering hose and soaked the air filter. I figured the afm was toast anyway so i bought a can of cleaner for the heck of it. Cleaned the sensor, and threw code 31, car ran like crap. Didn't surprise me. A couple days later the car decided it wanted to run perfect again. Drove great for a few weeks. Went on a 600 mile round trip. Car started to run a little sluggish, and wasn't making full boost. Decided to try and clean the afm again. Now the car wanted to run like the afm wasn't even plugged in, if it would start at all. Code 31. Put in a used sensor i got from eBay with a Lexus housing. (stock housing still on car.) No change. Car still barely runs. Still code 31. Turned boost back down to stock, and bought a re-manufactured afm, and installed. Runs good enough to drive the car, but it bucks, jumps, and falls on its face. Black smoke from exhaust, smells rich. Code 31. For the heck of it, i unplugged the cold start injector, but that of course didn't change anything. Replaced the afm plug and about 6 inches of wire. No change. Not sure what to do from here.

This is my first turbo car. I'm not to familiar with them, but could a vac/boost leak be causing the issue? I sprayed every connection and seam on the topside of the engine bay with the can of MAF sensor cleaner, but couldn't find a vacuum leak. I haven't gotten under the car to check yet though. About to pull my hair out. Just want code 31 fixed and the car to run good warm. Dont care about the cold start issue.

 

[3p141592654]

It seems pretty clear what the problem is: code 31: open or short circuit in air flow meter circuit. Since the AFM is a primary sensor for the ECU, it will never run right with a code 31.

It ain't a boost leak or anything else. Since you've replaced the AFM multiple times, they're either all bad, or you have a wiring issue. Check continuity from ECU pins to AFM connector pins.

 

[Bmettie]

I've also heard terrible stories when using MAF(Mass Air Flow) cleaner on Supra KV AFM (Karmen Vortex Air Flow Meter),which should never be done. Stories just like yours....

There's a little mirror in our AFM's that gets destroyed by MAF Cleaner

 

[chevyguyjoe]

I've also heard terrible stories when using MAF(Mass Air Flow) cleaner on Supra KV AFM (Karmen Vortex Air Flow Meter),which should never be done. Stories just like yours....

There's a little mirror in our AFM's that gets destroyed by MAF Cleaner

I understand. As i said the sensor was covered in oil, so i figured i had nothing to loose. AFM has been replaced multiple times since then.

 

[super51fan]

All the AFM could be junk. I would not waste my money on a reman unit. I would not waste my money on a used one either. The code refers to the circuit as someone has already told you. You need to carefully look at the pins of connector and check for continuity of the wires going to the ecu. We are lucky with toyota products that most codes are caused by failed parts. However the code can be caused by wiring issues. If you don't have a good DVOM meter i suggest you get one.

 

[Nick M]

I've also heard terrible stories when using MAF(Mass Air Flow) cleaner on Supra KV AFM (Karmen Vortex Air Flow Meter]

It is not a story. The oil gets on the optics. And in my case, I realized I was not getting the karman effect.

 

[chevyguyjoe]

Thanks for the help. I guess ill get out the multimeter and start checking. Im typically a carburetor and distributor kind of guy. Chasing electrical problems is not my forte.