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My '99 NB starts fine from cold but has become hard to start when hot. Battery seems fine and after doing some research I suspect the CAS is at fault when it gets hot. Make sense?

Firstly can anyone confirm that the CAS is the small black plastic thingy with wires attached and fixed with one bolt to the front of the cam cover drivers side? I tried cooling it down with a damp cloth and the car started fine but it may have been a coincidence so I will try the same trick again after driving again to heat it up.

Are these a pain to replace or do they just slide out and the new one slides back in? Anything to watch for re fitting?

Thanks for any help.

Yep definitely the CAS. Its a common problem and an easy fix, it seriously takes about 10 seconds to replace.

You undo the screw, unclip the plug, pull out, put new one in, put screw back in, plug the wires back in and done.

A good test is what you already done, when its hot if it doesnt start put something cool/cold on it and it should fire up straight away, when the sensor ages it gets easily affected by heat.

Contact MX5 Mania, they stock them and are a really good price.

Thanks.....do you need to mark the exact position on the cam cover before removal to line the new one up properly as it is on a 45 degree angle to the right?

I read somewhere that u need to remove the cam cover but I can't see why you would need to do that....possibly refers to another model other than the NB.

I am just going through the same thing ATM. I firstly replaced crank angle sensor and it seemed to fix it but it did it again. I have just replaced the cam angle sensor and have ordered a new EGI relay. So far so good. I got my gear from mania, good price and super quick delivery. I also had the car scanned and it registered a cam sensor fault to.
I hope you get yours sorted soon

John - give Pete F a call. I think he has a spare that he doesn't need, and he's just around the corner.

[quote="Guran"]John - give Pete F a call. I think he has a spare that he doesn't need, and he's just around the corner.[/quote

Thanks Bryan....I am not dead certain this is the problem as I have not been able to replicate it. Starting ok hot at the moment but it could be because I have been tapping and cooling the CAS so it probably is the guilty party.

When it happens again (& these things usually do)I will try Pete & replace it.....thanks

Shouldnt need to line anything up, it only goes in one way, well it does on my nb8b anyway, I assume the nb8a would be the same its just the location is different, mine is on top of the rocker cover, driver side near the firewall where is yours is on the front of the motor.

When its previously done it, has it been a really stinking hot day or just normal hot? Normally they will only play up when the sensor gets really heat soaked, so a hot day, long driving periods, hard driving, stop start traffic etc.

Yeah...makes sense coz I had been doing some hard driving and the sensor was pretty hot to feel when it was hard to restart whereas I took it for a short run later and the sensor was not so hot and it started ok.

I will go for another hard drive to get it really hot to touch and see if I can replicate the starting problem and then immediately cool the sensor again as before to see if it starts ok.

These intermittent problems are a pain in the a%#e....

Thanks for your help....

wiz043 wrote:
These intermittent problems are a pain in the a%#e....

Tell me about it lol Iv had and still got a few intermittent issues with my nb8b but luckily for me they are nothing serious and still runs perfect. Then when it goes into the mechanics to get it checked it runs perfectly and wont act up lol.

the heat thing is I reckon debatable- the car gets hot very quickly i.e. correct operating temp.

Hi John (wiz043), any updates after replacing the CAS? Did it solve the starting issue?

I managed to get a used cam angle sensor at reasonable cost from a fellow club member and so far it appears to have solved the problem (touch wood).

I think new ones from Mazda cost over $200 so hopefully I have dodged a bullet.

Thanks for interest.....

They're $60-70 including postage from Mania, brand new Mazda part.

Suspense wrote:They're $60-70 including postage from Mania, brand new Mazda part.

Luckily....I got mine cheaper than that second hand but according to Mania's website they are $158.72, that's why I went looking elsewhere. They are also called camshaft position sensor.


http://www.mx5mania.com.au/oemparts.php#Electrical

Prices on the website aren't updated frequently. You need to pick up the phone or check their eBay store if you want a particular part.