1st MP3 in NH

OK I retested the impedance of the IAC it reads out to 8.6 omha.
I disconnected it and removed it from the car and let it warm up for a half hour.
Now on to check for shorts.
Does anyone know which pin of the ECU is supposed to go to which pin in the harness? The shop manual says to check for shorts and open circuits but if I have the right connections and there are now other resistive element in the path then I should get short circuits.

1st MP3 in NH

I just rang the wires form the IAC harness to the ECU. I had the brown wire ring directly (.3 ohms) to pin 54 and the grey wire rang directly (.3 ohms) to pin 83.
Neither wire rang to each other or ground.

I assume with this the IAC must either be dead or is working fine and something else must be to blame?

1st MP3 in NH

After removing, cleaning and reinstalling the MAF and IAC and a computer reset I started the car and to my amazement it actualy started and idled fine. I then removed the hire clip for the IAC and the idle crashed and I quickly replaced it and went for a drive. It acted no differently then it did before. It will still crash if you use the clutch quickly at high speeds and dip severely at lower speeds. After the drive I again removed the IAC cwiring clip and this time the idle did not fall a bit.

So I am back to where I was.

Just two more tid nits. IF I cover the MAF with my hand the car stalls, fast so there are no intake leaks. If I blow into the MAF the car also stall, I have no idea what this means but I figured it couldn't hurt to mention.

Phantom Cruiser

We had terrible idle issues before we installed our BOV (on our Focus). It would barely stay running when idling. We installed the Greddy Type-S BOV and it cured the problem.

rodslinger

I'm thinking something related to the BOV also. You said it is a recirculating type but where is the return located? If it was vented to atmosphere I would have guaranteed it was leaking and throwing off the MAF reading at idle. Is the return close to the MAF? Maybe turbulent air near the MAF giving false readings? I would pull out the BOV and plug the lines and see what happens.

dewey

FWIW, my '93 Pro DX, and also my wifes (same year and trim line) also exhibited these symptoms: off the gas or on the clutch at high speed results in a stall or near-stall. Not every time, but frequently.

We have not been able to find the problem and neither has the Mazda dealership.

We've tried most of what it says to check in the shop manual. I can't recall if I checked the IAC switch or not. I don't even know if they had 'em back in '93.

At any rate, I have checked lots of switches and valves, but I haven't replaced anything, and I haven't found the problem.

1st MP3 in NH

Just as a possible ray of sunshine for all the people experiencing these issues, and the count is now in the double digits. Thursday I am taking my car into a dealership I very much trust to help and be honest. THe service manager runs a great crew and is a personal friend. Unfortunitly its not a Mzda dealer so I am probably going to get nailed by the bill. Either way, the service manager also has a Protege doing this, he used to work for a Mzda dealer for several years, So he is personaly interested to find the problem.

carguycw

I have heard of 90-93 1.6L Miatas having problems with their IAC valves, and the 1.6L Miata uses a very similar EFI system to the 90-93 Protege (both use a flapper-door VAF instead of a hot-wire MAF sensor like later Proteges and Miatas). It would not suprise me if Proteges suffer from the same problem.

Try checking for info in the "1st Gen Engine & Drivetrain" section.

Back to the original topic, I also think that the BOV is a likely cause for the idle problem. I hand't really thought of that b/c I haven't done much work on turbo cars.

1st MP3 in NH

OK heres the news so far. Car is at the dealer and they assume a MAF malfunction.

The engine is throwing code #P1504.
I guess this is an Air fuel ratio code?

FM ruled out the blow off valve since its a recirculating one and there is definitly no leaks to the atmosphere.

1st MP3 in NH

Well for those keeping track, the dealer has diagnosed the problem to be the computer, it is not passing ground for the ground pin of the IAC. The computer is aparently fried.

THey have a new one on the way