mx5 mk1 na cold misfire ,running rich

 Hi I have a mk1 mx5 na, and im having a few problems if any one can help I’m new to mx5.

  1. A missfire when engine is cold, the car starts fine and idles fine but if you
    Rev it a bit it starts to misfires and shakes all over the place both on idle and reving it up. But after a few minutes its fine and can be driven no problem idles good and pulls fine.

  2. It seems to be running rich all the time, quite a bit of white smoke takes a while to clear.

I have checked and replaced lots of things but But no look and now don’t knot were to turn.

Inc new
Head gasket
Timing belt
coil pack
ht leads twice
Plugs twice
o2 sensor
ecu temperature sensor

Cleaned afm
Cleaned throttle body
Pulled injectors out tested them lose in rail spay pattern good on all 4
Checked vacuum hoses
Cylinder compression #1 168psi
#2 158psi ,#3 171,#4 169psi

No fault codes

Checked all earth points

Fuel cleaner added to tank.

I have no idea where to turn after all that
If any one can help that would be amazing as it was suppose to be a xmas present for my wife

 Welcome to the FUN 

 Sounds like a faulty Mass Air Flow Meter MAF. if it’s gone no amount of cleaning it will make it right. See if you can swap one over from another MX5 to confirm the issue.

 Lot’s going cheap on ebay so it won’t kill your bank balance. 

 Good Luck with it

ok I have ordered one off eBay, I did check the signal wires from it and i was getting volts that increase with revs but could be worth a go.


im a bit worried about the amount of white/light grey smoke and water coming out of the exhaust even when warm, it does clear when driving but stop for say 10min and when you start it back up it smokes again. I changed the head gasket fearing that was the cause but now im not sure if its water coming from coolant system or water vaper condensing because its running very rich.


any ideas guys

hi all today I changed the afm and injectors for used working ones. No affect. Were can I go from here.


could a faulty tps cause this. Just seems weird its only misfires for the first min or so.



if any one can help were to go next that would be awesome.


many thanks

1 Like


I have exactly the same problem with my Miata mk1 1.6 16v…
I’ve Nevers find the reasons…
Did you resolve this issue ?
Thanks a lot…

As there is an issue that appears to be a misfire but no error code, I would check the ECU.