mx5cartalk.com

CAS, CAZ, CASH (you know who you are) for the BP4W are not all the same.

For those who don't know I'm running a Haltech PS100. This year, since about May the car has been having an intermittent miss issue that developed at high RPM's after a time of heavy track use. The miss would progressively get worse until the car could only be dríven below 4,650 RPM. Changing the Cam Angle Sensor (CAS) would see the issue go away only to develop again after some high loads at the track. The failed sensors could be put into another NB and have no issues.

So on the dyno the failed sensors have been tested with all the filtering options available but a failed sensor can never be made to run in my car again, but they work fine in other cars. Therefore, it would appear to be on the surface a Haltech specific issue, not the full story!

Mazda have superseded the CAS part number BP4W-18-230 with ZJ10-18-221. No for the kicker, the new part number (ZJ10-18-221) is the one the eventually fails whereas the BP4W-18-230 part number has only failed once and was replaced by the new part number in May! So it would appear that the miss COULD be a combination between the PS1000 and the new part number. Haltech have been contacted to discuss the issue and hopefully there will be a long term fix. However for me I need to stick with the old part number.

This has been a very frustrating problem and it is good to have an explanation, it is not a solution but a very large step in the right direction. Now people could attempt to lay blame in lots of different places, that is not the purpose of this post. The purpose is to help others if they have a similar issue.

To test the theory above I have 3 CAS's from different sources, OEM (old part), MX5 Mania and Repco. If the OEM fails at WTAC I will swap it out for a different one and see what happens.

1. J5T23181
DSCN2803 by Eipeip, on Flickr

2. ZJ10-18-221 (never to be used again)
DSCN2804 by Eipeip, on Flickr

3. J5T30772 (Sold by Repco/Supercheap RAE part no SC271)
DSCN2807 by Eipeip, on Flickr

4. J5T30773 (Sold by MX5 Mania)
DSCN2805 by Eipeip, on Flickr

I replaced mine in my NB8A due to a miss at 4500 rpm+ when hot but it turned out to be a fuel problem with clogged fuel pump sock (inside the tank) and filter (under the drivers seat)...nothing to do with CAS.....

AndrewM that is what we thought the problem was, but no issues with the fuel side of the car.

I'm running a Toda adjustable timing gear which has 'nubs' for the cam angle sensor. Now this maybe a red herring, but if Mazda has changed the Cam Angle Sensor from J5T12181 to ZJ1018221 what else in the valve train has also changed.

Looking at Mazda part numbers J5T12181 is no longer listed and I can't find when it was superseded. However, it would appear in 2001 the timing gear part number also changed.

Model CAS Timing Gear
1999 ZJ1018221 BP4W12425
2000 ZJ1018221 BP4W12425
2001 ZJ1018221 B6S712425A
2002 ZJ1018221 B6S712425A

Maybe it is time to get an OEM timing gear pulley, the Toda adjustable and each of the different cam angle sensors and see if there is a difference in this. But why is this only happening to me...

Here is the solution if you don't want the expense of a cable tie This has not missed a 'beat' yet despite being left idle for 10 mins or longer at Noosa Hill Climb. Track test will be at Lakeside on Monday but it is looking good!

With this solution I can plug back in the OEM CAS sensor (complete with cable tie)

IMG_1159[1] by Eipeip, on Flickr

Magpie wrote:AndrewM that is what we thought the problem was, but no issues with the fuel side of the car.

I'm running a Toda adjustable timing gear which has 'nubs' for the cam angle sensor. Now this maybe a red herring, but if Mazda has changed the Cam Angle Sensor from J5T12181 to ZJ1018221 what else in the valve train has also changed.

Looking at Mazda part numbers J5T12181 is no longer listed and I can't find when it was superseded. However, it would appear in 2001 the timing gear part number also changed.

Model CAS Timing Gear
1999 ZJ1018221 BP4W12425
2000 ZJ1018221 BP4W12425
2001 ZJ1018221 B6S712425A
2002 ZJ1018221 B6S712425A

Maybe it is time to get an OEM timing gear pulley, the Toda adjustable and each of the different cam angle sensors and see if there is a difference in this. But why is this only happening to me...

Bear in mind that in late 2000 the NB8B came out with the Variable Valve timing thingy, which from memory is operated by a solenoid or something built into the intake pulley. That may explain the part number change in 2001. The fact that the CAS number remained the same tells me that the triggering method was also unchanged.

from memory the NB CAS is a magnetic sensor isn't it? is it possible that the Toda nubs are also magnetic and causing the sensor to be magnetised and give a wrong signal or something? (pretty sure the OEM pulley is simply a ferrous metal and has nothing constantly magnetic in it)

hks_kansei possibly the Toda cam gears could be causing the problem, however it is not uncommon for people to install these hence the issue would be more widespread.

In discussions with others it could be that the plug due to its age is not making solid contact length ways all the time, hence why the cable tie works. It pulls everything in tight.