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Hey forumites,
I am having problems with my NB8B cutting out when it has been running for a while and would appreciate some input. The car drives like a gem for up to half an hour then starts to cough and splutter, runs really rough for about 10 seconds then dies. The engine turns over but will not fire. After about 5 minutes it starts and will run for a short distance then it happens all over again.
The fact that the car can be started after a short rest indicates to me that something is overheating and causing the cut out. My mechanic has checked the computer for fault codes - there are no codes logged. He replaced the fuel pump a couple of weeks ago but that was obviously not the source of the problem.
My mechanic has decided that there can only be a few issues causing the problem. In the electricals box under the bonnet on the offside there is a green component which gets really hot. The other areas he thinks could be the problem are the crankshaft positioning sensor and the camshaft sensor.
My mechanic is a wizard with all things mechanical. He maintains a number of race cars and is a pretty good race driver so I trust his judgement. He has had the car running in his workshop but so far has not been able to recreate the problem.
The NB8B has done big mileage - just over 220,000k's so I guess things which would not normally be a problem are starting to wear out. It is a delightful car to drive but I need to know when I take it out for a run that it will get me home.
Any ideas/suggestions/inputs?

I think Sliq had a similar problem..

(have a read here)

It turned out to be the camshaft angle sensor.

What RawSouth said.

I'm having the exact same problem with my NB8B. The first time it happened to me was at Jenolan caves during the MX5 Club NSW 500km run last year (some of you might remember ) and in that case I figured it was overheating due to low gears and high revs. I left the car to rest for fifteen minutes and then it started again, and I was able to make it all the way to Goulburn then back home again without another issue.

It happened again yesterday (when I was in the Hills area, and it was over forty degrees). I drove the car in the morning to Baulkham Hills, was able to drive all that morning around the area, and then when I pulled into my boyfriend's driveway it stuttered and died - originally we thought I had just stalled, but when I tried to start it again, it turned over and ran for a few seconds in neutral, then cut out again (this happens when I start it in both neutral and first gear, clutch in). We left it to rest for half an hour, then managed to drive it to Windsor Rd, and after about another hundred metres it cut out again. All of my temperature gauges are normal when this occurs. Anyway, this happened twice more that afternoon before we found a shady carpark at Castle Hill to leave it in for half an hour. I drove it back to boyfriend's house (about 3km), and there wasn't an issue. I waited a few hours because I wanted it to be later and cooler before I drove all the way home (without turning the airconditioning on, just in case) and had no problems on that drive either.

I can't help thinking that this problem only happens when the conditions are hot. My boyfriend thought it might be the injectors, or maybe a bad batch of fuel. And my dad says it could be an electrical problem.

I'm speaking to my mechanic today, but if anyone else has any ideas as to how we can cure our cars, or at least what the problem is, it would be much appreciated

RawSouth wrote:I think Sliq had a similar problem..

(have a read here)

It turned out to be the camshaft angle sensor.

Ooh, thanks RawSouth!

I'll look into it! Mine is the exact same model as Mike's car (even the colour haha).

I'll report back!

Twiggy wrote:

RawSouth wrote:I think Sliq had a similar problem..

Mine is the exact same model as Mike's car (even the colour haha).

That makes 3 of us!

It is a known problem for the NB8B
On the big forum it is known as "Got Buck" amongst many other threads.

The Camshaft Position Sensor is available from either MX5Parts UK or from finishlineperformance in the states.
Or your local Mazda dealer will be happy to lighten your wallet in exchange for the part.

Takes about 5 minutes to replace, 3 of that is finding a suitable spanner and taking it out of the box

RawSouth wrote:

Twiggy wrote:

RawSouth wrote:I think Sliq had a similar problem..

Mine is the exact same model as Mike's car (even the colour haha).

That makes 3 of us!

Ahem... 4!

Similar problems on my car were caused by the EGI Main relay (the big green one in the fusebox under the bonnet)

Also I had slightly less dramatic symptoms a while back of the car feeling sluggish, which turned out to be the ECU retarding the spark because the coilpacks were dodgy. I replaced them and the cam angle sensor at the same time, and the car is now awesome (although on *really* hot days it runs very rich, so I suspect the O2 sensor is not performing at its best)

My car has done > 240000km so it's been around the block a few times

The work shop manual will go thru a full cross check to determine the fault and "your: mechanic needs to go thru that process. Problem solving has to be done with a process and the manuals should lead to the answer.

Mr Morlock wrote:The work shop manual will go thru a full cross check to determine the fault and "your: mechanic needs to go thru that process. Problem solving has to be done with a process and the manuals should lead to the answer.

Unless it is a known problem experienced by most vehicles in the same series, all having very similar symptoms!

In fact the workshop manual provides very little guidance on this particular problem and based on the responses to threads on both this site and the big forum, Mazda technicians haven't got a clue either!
As many who have experienced this problem will attest, they have generally started at the fuel pump, followed by replacing the Crank Sensor followed by scratching of head until they finally replace the Cam Sensor. An expensive way to get to a simple fix.

The advantage of a forum is to tap into the experience of other forum members who have experienced a similar problem with the same vehicle and have rectified it.

All recommendations on any forum are generally provided to the OP in good faith and is then up to him/her to accept and act upon them as he/she sees fit.

If the recommendation is run off to your Mazda dealer / local mechanic every time we have a problem, what is the use of asking any questions on the forum!

^Well said De Bounce!^

Twiggy wrote:

RawSouth wrote:I think Sliq had a similar problem..

(have a read here)

It turned out to be the camshaft angle sensor.

Ooh, thanks RawSouth!

I'll look into it! Mine is the exact same model as Mike's car (even the colour haha).

I'll report back!

i have a spare working one here, you are welcome to come and try it out. I live in Peakhurst, so not too far from you. Shoot us a PM if interested

Thanks all respondants, I appreciate your input. We are going to replace the cam sensor and the EGI relay and I am looking forward to the problem being solved. See you all on a run somewhere, someday soon.
David

djw24s wrote:Thanks all respondants, I appreciate your input. We are going to replace the cam sensor and the EGI relay and I am looking forward to the problem being solved. See you all on a run somewhere, someday soon.
David

Please don't forget to come back and post up the results

I will most certainly let you know the outcome. My NB is in the spray painters from today having a brand new coat of Garnett Red applied to it after the previous paint job went belly up with a bad batch of hardener in the clear coat so it may be a week or so before I get back to you. Given that this engine problem may affect more than just my car and being a firm believer in sharing information you will see the final result.