Check the O2 sensor voltage, my bet is that it's goosed.
Aha! Could be that, then. Shouldn't be hard to check with a multimeter whether it's switching or not.The 1.6 TPS also has an 'im closed' switch so it knows when to idle, and presumably when on the overrun.
take the idle screw out and clean= thouroughly,if not that its the lambda probeMy Eunos (NA 1.6) over the last couple of months has developed a misfire on overrun.
It doesn't miss under load (or at least, if it does it's so subtle I can't feel it), so I'm discounting the idea of an ignition fault, as ime these tend to show up under load.
Possibly related, ever since I have had it, once at operating temp and normal idle (around 900rpm) it wil randomly fluctutae at idle. This improved when I reset the base idle, but it still does it, and the miss on overrun is always there, cold or warm.
The guy before me (& Madda), replaced a few things to try to cure the erratic idle, but not really sure what he tried. So may have to start from scrathc in the respect.
Any thoughts? Vac leak maybe? I need to get hold of a Mazda tech manual so I can check signals from MAF, temp sensors, etc - but until then, just after some ideas? Is there anywhere to download a tech manual?
Also, I seem to get a lot of vapour from the exhaust at idle, even when warm. It's not gathering moisture when I put my hand in it and I don't loose any water, so I don't think it's that. It does smell pretty rich, but then I'm told these engines run a bit rich anyway?