Troubleshooting codes 8 and 10 on a 1990 Miata, pulled off some electrical tape and found this:



Code 8: Airflow meter open or short circuit

Code 10: Intake air thermistor in airflow meter open or short circuit


Any clue? Is it the shielding for the signal wire? Would that cause the codes I'm getting?

 

Shielding. It only needs to be grounded to the chassis or engine at one end, probably at the other end. In theory if neither end is grounded it may cause noise to enter the signals and the ECU throw a code. In practice, maybe not.

 

You'll want to be taking off the plastic cover to the AFM with a sharp knife around the glue. I'm guessing you'll find a disconnected wire or rusted something.

Is that Ohio State or Oregon State?

 

Neither! Oklahoma State.

I'm a bit apprehensive about fiddling with the AFM, as it's my DD, but it sounds like it might be the issue. Both codes point towards there being an issue with the AFM, which it wouldn't seem like that grounding wire would cause?

However, I'm only getting a small stumble off idle, and some uneven power up till 4k or so. I would think an AFM issue would cause bigger problems than that.

 

Ah. Change your spark plugs and wires. No if, ands, or buts about it, just do it if they're older than your last oil change.

 

Way ahead of you. Brand new NGK blues and plugs. I'll pull the top off the AFM when I get home. I got the motorcycle to ride just in case!

The only other thing I know of is the PO did an evaporative canister delete, because it was throwing a code for that. I haven't checked to make sure he did it properly, but I doubt it would be causing these issues anyway...

 

That shouldn't throw a code, at least it hasn't in the half dozen 1.6ers I'm familiar with.

 

26 Solenoid valve (Evaporative canister purge)

That's what I got.

 

Just popped the top off the AFM. Everything looks like it's supposed to. The vane moves without resistance. I disconnected the battery to reset the codes, so I'll see if I still get the AFM codes.

 

Just reset the codes. Only getting code 26 now. I did take the car to work and back, but I'll drive it some more and get it fully warmed up just in case.