Cranks but wont start Mk1 Eunos 1.6 auto

Hi everyone, I have enjoyed driving my mk1 1.6 auto for nearly 9 years now, but it has started to play up. It cranks strongly but wont run, no spark at any plug. The Autolink fault codes are 10 Intake Air Thermistor, 12 Throttle position sensor and 8 Airflow Meter. I have ordered a new aftermarket throttle position sensor firstly to see if that helps (£28 from Mx5 parts). The very experienced RAC repair man who towed my car told me it will be the crankshaft sensor. He said he has towed and fixed dozens MX5s and almost all are crankshaft sensors. We see if he is right.

Is there anything I should check before buying a used airflow unit?

Hi not sure position sensor would stop it sparking

I think your car has a sparky ignitiony thinglybobber to consider. Little black box…somewhere.
image
That’s from ancient memory…
Mx5 Parts want nearly £200. In a pigs lug-'ole.

Whilst I’m sure your AA man knows what he’s talking about, I don’t think the mark1 engines had crank position sensors. The Mk1 ran off something called the “CAS” Cam Angle Sensor that is at the back of the cam cover - it looks like a flat distributor about 3-4" wide.
If I were you I’d take a quick look in the passenger footwell to check that the ECU hasn’t got wet, then concentrate your diagnostics on either the CAS wiring, coilpack or ignitor (the thingamybob refered to above) which can be found on the side of the wing. Also don’t autos have a ignition lockout for starting when not in park?
Good luck :+1:

https://www.miataturbo.net/general-miata-chat-9/how-determine-if-igniter-coilpack-bad-63812/

Good thoughts,
just for info , the lock out on the auto stops it cranking/turning over when in gear and only allows cranking/turning over in Park or Neutral (preventing starting in gear).
If it’s cranking but no spark I would discount the auto side of things
I would think CAS or Ignitor

Something I saved from a previous investigation when my car wouldn’t start from a MX5 specialist…
"Could be a good handful of things.
first up look see if the cams are turning (snapped timing belt) pop the oil fill cap off and look inside while its turned over.
next if all fuses and relays are ok look for a spark, if none its more then likely the cas as said above but also can be the ignitor or the coils(however its rare for both coils to go at the same time so 2 of the 4 plugs will spark)
next bridge the diag port for the pump and ground (in the black diag box ) and see if the pump primes. you will hear it but if you want 100% to clarify pop the fuel pipe from the rail of and fuel will squirt out.
if you have a good spark, good fuel and the belt is fine im not sure what else it can be.

Had this problem on my wifes Fiat 500 and it was the Crank position sensor. Cheap to replace and easy to fit. Hopefully, it will just as easy for your 5.

Just discovered that the 1.6 auto has a different TPS Sensor (a four pin rather than the std mk1 3 pin). MX5 parts are refunding and adjusting their website to show (fits manual only). MX5 parts advice is that a breakers yard is the part is the only option! I will try dismantling and cleaning the throttle box to see if it fixes.

Hooray its running, I replaced the camshaft sensor with a replacement used one and it fired up faultlessly! The fault codes from the ECU were bogus!!

4 Likes

Great news :grin: