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I have had my 2002 NB at a Mazda service dept for the last 5 weeks whilst they try to sort a problem that is proving to baffle them and a Auto electrician. The car whilst i was driving just suddenly stopped i called a tow truck and had it taken to my residence where i pushed it into the garage and over the next few days tried to start it to no avail i did read the handbook which led me to think that the problem was to do with the immobiliser i arranged another tow to the dealer.They agreeing with me sent the immobiliser away to Melbourne for testing they said they found a loose wire resoldered it and sent it back, dealer reinstalled it started the car and it fired and still shut down. Since then they the dealer and Electrician have tested each wire running from the ignition to the engine and come up with this scenario if they run a screwdriver past the crankangle sensor and reinstall back into its position it starts and runs turn it off and on for 5/6 times then it goes back to starting and shutting down again.The dealer suggested i post this on the forum to see if anyone else has had this problem their suggestion at this time is for me to purchase a complete immobiliser and keys and try that at a cost of $500 plus the money spent to date about $450 and if this dont work im stuck with the part. Any ideas would be helpful im not mechanically minded and certainly dont get the electrics involved.
Thanks in advance for any HELP just want my NB back

Crank or cam angle sensor?

I recall the cam angle sensor (up on the rocker cover) is a realtively common problem.

If running a screwdrive past it helps, it may be a sign since the sensor works off magnets or something.


A replacement sensor is $100 or so from memory, alternatively contact the member "lightyear" on this forum, he's melbourne based and is currently selling a fair few parts, he might have one for sale cheap

Bump

What he said ^^^^

Crank angle sensor. Just replace it and you should be right. You may also need to change the cam angle sensor as it seems to fairly common for both to go at about the same time (one fails and stresses the other causing it to fail).

NB8B issues from most common to slightly less common tend to be:
EGI relay;
cam position sensor;
crank position sensor;
ECU; &
coil (more recently accoding to a couple of NB8B/D owners).

93_Clubman wrote:NB8B issues from most common to slightly less common tend to be:
EGI relay;
cam position sensor;
crank position sensor;
ECU; &
coil (more recently accoding to a couple of NB8B/D owners).

Earlier MX5 issues include above as well as:
Electrical connector at inside of top plate of fuel tank which affects the fuel pump (more common on NA, but not unknown on NB);
Coilpack wiring loom weakness - lack of support resulting in wires breaking inside plastic insulation (NB8A); &
Coilpacks (NB8A).

Ref EGI relay being an issue, a dodgy light bulb connector & intermittent faults with the tail & brake lights has in the past caused issues with the EGI relay, so make sure all electrical connections are ok including all earths.

Fuel pump in-tank wiring loom upper connector problem, due to the so called 'blackwire' issue: viewtopic.php?f=55&t=46425

irwin83r mentioned his NB8A cam angle sensor plug used to work itself loose once it got hot - he secured it by puting a cable tie around it - still ok years later:
viewtopic.php?f=19&t=23453&p=299175&hilit=cable+tie#p299175

Also have a look at what manga_blue found about metal particles bridging the terminals inside the fuel pump:
viewtopic.php?f=55&t=46425&p=822568&hilit=pump#p822568

These two posts probably cover most of the potential causes:
viewtopic.php?f=29&t=60295

viewtopic.php?f=29&t=67030