Mazda Miata: rough idle...

Hi,

I've a '93 1.8 eunos roadster that idles roughly and stumbles after warming
up. When on the open road she seems to have loads of power but as I haven't
driven another one I've nothing to compare it with.

I've already replaced the plugs and leads which made no difference. Also
I've been putting redex petrol treatment in the fuel and into the injectors
in case they're blocked. Still no difference.

I did the old paper clip trick on the diagnostics thingy and checked the
readings with a volt meter. There were a couple of errors there initially (1
and 8) probably because I was dicking about with the air flow monitor to get
the redex into the injectors.

I cleared the diagnostics by disconnecting the battery and took the car for
a spin. Now all the error codes have gone but the rough idle/stumble is
still there.

I'm not too sure what else to try. Things I've thought of trying but am not
sure if they'll make the difference are giving her a new air filter or fuel
filter. Or could it be the coils breaking down. I'm not sure which of these
things would be picked up by the diagnostics computer anyways. I'm a bit
worried that the longer I leave it, the more likely I could be doing damage
to the cat as unburnt petrol may be getting exhausted.

All help greatly appreciated.
Gav.

>I'm not too sure what else to try. Things I've thought of trying but am not 

Those are good possibilities. However, do test your Oxygen Sensor. If you have
the shop manual, it tells you how to do that just using the accelerator and a
volt meter.

I had the same symptom you do. Changing the OS did the trick. You can buy a
replacement at an auto store MUCH CHEAPER than the dealer. Dealer wants $200+,
while an auto store wanted like $30 :-P
~Cissy
<a href="http://members.aol.com/IvaMiata/Krikkit/index2.html">My '90 Mazda
Miata</a><br>
<i>I love PC adventure games</i>