mx5cartalk.com

Howdy. Does anyone in SE Qld (I live in Mackenzie, near Mount Gravatt) have an ECU for a 1989 NA that I might borrow over the weekend to do some testing for an issue I have been having with my car?

I first noticed the issue several months ago. Initially sporadic, the frequency has increased over the last couple of weeks to the point that it happens daily, but not on every occasion I start the car (maybe one-in-three).

The car cranks strongly as if it will start normally, but then sputters out. Can take between two to ten goes for it to turn over properly. When the car is running it goes along very nicely and recently set a new economy record of 6.25l/100km (15.99km / litre). Issue happens from cold start or hot start.
Have noticed also that sometimes the car starts perfectly, but when I put the car into gear it then shuts down.

Disconcertingly, on a couple of occasions (several months back) when I have been driving, the engine has completely cut out. I believe a gear change was in progress when this occurred. Turn the key again while the car is still in motion and it starts again.

I was looking at the ‘No Start’ guide on the miata.net garage. Because I work around the corner from Automotive +, I dropped in to see Dave and tried to isolate the issue by separately swapping out the AFM and the fuel injector relay. No good on both accounts. Dave said next step is ECU, but he was busy and I had to get back to work, so car booked in for next Friday. BTW, thanks for the assistance at short notice, Dave!

Was hoping that maybe I could borrow a spare ECU from a forum member over the weekend to see if that makes a difference.

Also open to any other ideas.

Have you had a look at the ECU to see if it's wet? You should be able to see if the surroundings are dry and corrosion free.

Re ECU, you can even remove the top & bottom covers to visually check the printed circuit board & components for anything that looks suspect.
Re below (cutting out when depressing the clutch & engaging or changing gear), check the switch activated by the clutch pedal as they have been known to disintegrate.

BlackLeaf wrote:Have noticed also that sometimes the car starts perfectly, but when I put the car into gear it then shuts down.
Disconcertingly, on a couple of occasions (several months back) when I have been driving, the engine has completely cut out. I believe a gear change was in progress when this occurred.

93_Clubman wrote:Re ECU, you can even remove the top & bottom covers to visually check the printed circuit board & components for anything that looks suspect.
Re below (cutting out when depressing the clutch & engaging or changing gear), check the switch activated by the clutch pedal as they have been known to disintegrate.

BlackLeaf wrote:Have noticed also that sometimes the car starts perfectly, but when I put the car into gear it then shuts down.
Disconcertingly, on a couple of occasions (several months back) when I have been driving, the engine has completely cut out. I believe a gear change was in progress when this occurred.

x2 on checking the clutch switch.

Provided they're not badly water damaged some ecus have come back to life after taking the covers off and giving them and their connecting plugs a drenching with electronic circuit board cleaner. JayCar sell a good one https://www.jaycar.com.au/electronic-circuit-board-cleaner-spray-can/p/NA1008 Use almost a full can.