mx5cartalk.com

The car is an NB8A with 129ks. Timing belt was done at around 105k's. The symptom is: car has warmed up you accelerate it feels like there is a lack of power then suddenly it takes off, then when you take your foot off the accelerator it feel like it is going to stall. It does not misfire just this sudden power on power off. (no it doesn't have a turbo!) Turn it off then come back in a few minutes and the car starts and runs as normal.

Got a price on cam sensor $160 and crank angle sensor $160 and I know coil pack is expensive. Before I start down any road of replacing them one by one any suggestions to identify which of the (common) 3 things it might be?

My cam angle sensor died at around 150k km, the engin stutters and loss of power then off especially when hot etc.
I think other people have had issues with this on NB8Bs with >100k km you will find other threads about this.
(At the time it feels like there is no fuel going into the engin and stutters giving up)

The crank angle sensor needs to be gapped with a feeler guage, when out of whack car wont start, I learnt this while doing a T belt change.

I have COP on NB8B now 250k km no glitches so far.

Try and borrow one for a weekend from somone off the forum before you go and buy them.

OP's car is an NB8A.....


You can use a hair dryer on the 3 items to determine if it worsens the problem when they get hot.

If you haven't already, I'd also throw a new set of plugs and leads on as this is relatively cheap and may eliminate one possible cause..

also, you can get new coil packs from MazdaSparesLtd in the UK posted in 4 days for UK$96 + UK$30 postage which works out all up about AUD$200...
Sure beats the $800 Mazda want to charge...

x2 for Wun's suggestion. Put two similar cars side by side in the garage and start swapping parts until something is fixed. Otherwise you can spend ages and a lot of cash changing things unnecessarily.

Have you scanned the fault codes yet?

Many thanks for the suggestions - great to see the forum in action. Will try the hairdryer suggestion.

I hope this isn't too OT or a hijack, but (and I'm not saying the Cam sensor is at fault) to me this cam sensor thing seems to be the most common failure on NB's.
Why? Heat? oil? vibration? all the above?
Is it a magnetic or optical sensor? or other?

Monte5,

I have my old cam sensor from when I went about changing parts cos my NB8A did strange things. It should still work and I can post it out to you if you're desperate or pickup in Sydney. I also have my old coil pack which, again, should still work. My crank sensor was damaged though so that doesn't work

I agree with manga_blue, try all diagnosis and fault codes etc first because you'd feel pretty foolish when the solution is an easy/cheap fix. Mine turned out to be the TPS...