Hi, I am looking for some ideas / help with my mx5 mk2.5 1.8 on a 52 plate. I bought the car as a non runner so have never heard it run. The person I had bought it from was using it as their daily driver then one day it would not start so they cut their losses and sold it as they did not want to pay garage fees to put it right. It is on 110,000 miles. I have just tried to start the car for the first time to see what would happen. I have put a fresh battery on it and the engine cranks over nicely at a healthy speed. Unfortunately the engine doesn’t catch. It spluttered a couple of times but only for a second then went back to cranking. There is a strong smell of fuel from the exhaust so I am confident it is not a fuel issue. I have yet to remove the spark plugs and check for spark as I was on my own, but I am pretty convinced it will be a spark issue rather a fuel or air issue.
After the trial I plugged in my Bluetooth obd2 reader and scanned the ecu for fault codes. Admittedly this is a cheap eBay reader which works with the torque lite app but it reported back no faults found / no codes.
The mk2 suffers with Crank sensor issues according to the technical faq’s but I could see nothing on the mk2.5. If a sensor was faulty would it show a fault code? Or would the car need to be plugged into a laptop running more advanced software to show a fault, or an inconsistent voltage at a sensor?
I am not a mechanic but have owned several mx5’s and the turn over sounded healthy. I have a multi meter and don’t mind doing some tests if people have suggestions.
The other idea I had was an immobiliser fault. The car has both its original keys. I once had an issue with a mk2 I had a key cut for with a faulty chip. That started then cut out immediately and illuminated the red key light. As it spluttered a few times I am not sure immobiliser fault is particularly probable.
As with any question like this I will update the thread when I find the answer. Nothing more annoying than someone with the same issue who never completed the thread and explained what their case boiled down to.
Thanks in advance!
I recently had a real problem with my mk1 it would cut and recover and finally died coil pack no ,igniter no finally changed cam sensor and it burst into life I realise that a 2.5 is different to mk1 but it must be worth trying both cam and crank sensors . I went through the whole ,plugs , leads possible immobilser bit and was close to arson or suicide !
Hi, Thanks for the input. Update; I have bought a used crank and cam shaft sensor from a running vehicle. Swapped the cam shaft position sensor no problem, the existing one looked fairly new. Tried to start the car, no change.
Went to change the crank sensor and the bolt was horribly rusty. In an effort not to strip the head off I have walked away from the job and will return tomorrow once I have bought some nut removal sockets. The more metal they have to bite into the better. Going to have to pick up a new bolt from Mazda so I may be finishing the job next week. The sensor does not look good nor do any of the pulleys. Everything is very rusty on the front of the engine.
The saga continues for now but the crank sensor is looking likely. Fingers crossed what is left of the 10mm bolt does not cause more headaches! I hate rust!
Final update, it was the Crank position sensor. Swapped the part which was overly difficult due to the rusted bolt holding the sensor in position.
Couple of tips for anyone else doing this on a mk2.5. Unbolt the fan to give yourself more access to the sensor. This was simply 2 bolts at the top and it can be lifted out the way. Also remove the air pipe between the throttle body and the airbox. The sensor is obstructed by a belt so I used a ratchet extension to give myself room and pushed against the belt enough to get the socket to seat down correctly.
The sensor connector is clipped to the car via a little plastic push fit clip, this is removed simply using a screwdriver to push the clip wings in to allow it to get back through the hole in the bracket. Then force the clip off the connector using a flat head screwdriver as you need to reuse the clip for the replacement sensor.
The sensor cable routing is tricky as there are lots of pulleys and belts very close by. I used the existing guide that’s like a hoop of bent metal at the top then cable tied the rest away from the belts and pulleys.
To remove the rusted bolt I used bolt removal sockets from screw-fix which were erbauer branded and cost £12. I snapped the old sensor off the bolt to get better access onto the head of the bolt. The sensor was brittle so this wasn’t too difficult.
Did this all from above to save lifting the car up and taking the under tray off.
The new bolt was £4 from mazda and they had to bring it in as its a non stock item. Only took 24 hours. Expensive for a bolt but essential to complete the task.
Hope this helps someone in the future!