MAF testing.....what should I see?

Hi All,

My 1.8 MK1 Eunos smells like its running very rich so I’m just running some basic checks before I replace the cat.
What should I be seeing at the 5 wire MAF sensor?
I get 1.3v at idle rising with revs for the flow sensor and a constant 2.6v from the IAT.
I’ve read a lot of contradictory info on these figures including that they should both be below 1V at idle?
Is there a resistance value I can check across the IAT?

Any ideas?

Many Thanks


The resistance across the IAT sensor (terminals C &D) should be 2.21-2.69 at 20*C (check in on Wednesday depending on where you live).

There are only 2 voltages given for the MAF signal, below 1v with the ignition on and 1.0-2.0 volts at idle. The WSM says to check the voltage at the PCM terminal which is terminal 2O. Terminal 2F should be below 1 volt. I’ll correspond those with the wiring diagram later and give you wire coloursif you like so that you can check the voltages at the sensor connector in the 1st instance.

Cheers Robbie,

That has certainly got me further along:)
I’ve been back probing the connector, so will check for below 1V with just the ignition on from the MAF output and then disconnect and check the resistance across the IAT.
From what you have said, my 1.3v from the MAF at idle looks within spec which makes sense as there are no major drivability issues, but a dodgy IAT reading could contribute to it running a bit rich i guess.
I think I’ve worked out the wiring colour wise, but where is the best place to get a decent workshop manual with comprehensive wiring diagrams for a 93/94 1.8 eunos as I’m going to be fitting an ME221 in the near future that’s been in its box for over a year!

Thanks again for your time it’s been a big help,


Hi Simon, I have a Wiring Diagram WSM for the 94 MX5 and the MAF diagram is covered on pages 32 & 33.
You can find WSM on line, think it is at mellons or something similar, link on here somewhere.
If it would help PM me an email address and I will scan the pages for you.

Cheers Dave,

I’ll google it and see what I can find, I’ll PM you if I get stuck!

Thanks matey

Simon …WSM…got it :grinning: