MAF Sensor Voltages

[luis.martins]

Hello everyone,

This is my first post, I've been using the forum for research purposes and now I need some help.

I've been trying to find the cause for too high CO emissions - over 0.8 when the value should be around 0.03 I believe.
The car is a MX-5 NB from early 2000 with a 1.8 (non VVT) engine with 100k miles on it.

I've changed the coolant temperature sensor, thermostat (which failed always open and the engine was running cool), spark plugs, air filter and still get too high CO emissions. My next bet is the O2 sensor and the MAF. Other than that, I'm clueless.

I measured the voltages on the MAF and the results are:
- Idle (around 850 RPMs) - 2.04 volts
- 3000 RPMs - 2.50 volts
- 5000 RPMs - 2.89 volts

Do these values sound right to you?

This evening I'll clean the MAF and measure again and will also try to measure the voltages on the O2 sensor.

BTW, I'm also getting a very low mileage, around 18 mpg with very moderate driving, when I should be getting at least 24 with this driving style.
I still remember how to do 10 mpg, but that is a story for another day...

Cheers,
Luis