NB8B hot day idling problems

Neilus · Postby **Neilus** » Thu Dec 19, 2013 12:53 pm

So at the tail end of a 3 hour drive today my NB8B started coughing and either refusing to rev or doing it very erratically. It felt almost exactly like the heat had gotten to my CAS but both the CAS and main relay were replaced a few months ago after the last time the heat made my car stop. I hit the CAS and green relay with a fair amount of electronic freezer spray when i got home and it didn't seem to help. Are the fuel or pump the likely culprits or are there other known heat related nb8b issues?

93_Clubman · Postby **93_Clubman** » Thu Dec 19, 2013 5:02 pm

If it's not either of the EGI relay or CAS you replaced a few months ago, then I'd replace the other CAS before the fuel pump. One CAS is the cam position sensor & other CAS is the crank position sensor.
ie CAS/crank position sensor:
http://www.ebay.com.au/itm/Genuine-Mazd ... 1938wt_985

as opposed to CAS/cam position sensor:
http://www.ebay.com.au/itm/Genuine-Mazd ... 20d29f213a

tescoking · Postby **tescoking** » Thu Dec 19, 2013 6:06 pm

Maybe the IAC sensor is getting old. I had this before, after service and drove 4.5 hrs for roadtrip and the car just like yours.

Neilus · Postby **Neilus** » Thu Dec 19, 2013 6:29 pm

It's a strange issue this time around. It was well hot today and I'd been on a long drive so I thought it was another failing part made worse by heat but the car's actually sputtered a second or so each time I've started it cold the last 2 days.

Will a failing Crank Position Sensor start working again if I cool it with freezer spray so I can diagnose it?

tescoking · Postby **tescoking** » Thu Dec 19, 2013 6:44 pm

Neilus wrote:It's a strange issue this time around. It was well hot today and I'd been on a long drive so I thought it was another failing part made worse by heat but the car's actually sputtered a second or so each time I've started it cold the last 2 days.

Will a failing Crank Position Sensor start working again if I cool it with freezer spray so I can diagnose it?

Don't try to freeze it, they are plastic and it could crack. Under normal temperature the computer should be able to read the sensor.

Mr Morlock · Postby **Mr Morlock** » Thu Dec 19, 2013 6:48 pm

if you can get the car to do it again with a qualified person at hand you might actually be able to diagnose the problem rather than just replace things. Also some of the links with so called OEM parts are not the real deal. Check the Mazda workshop manual for diagnosis -93 has probably got a link- its very good written by Engineers with full trouble shooting and how to do. Many things of course we cannot do without the equipment. Incidentally just because the day was hot it does not necessarily mean there was any connection to the problem.

93_Clubman · Postby **93_Clubman** » Fri Dec 20, 2013 10:16 am

Neilus wrote:Will a failing Crank Position Sensor start working again if I cool it with freezer spray so I can diagnose it?

Wouldn't rely on this method as a definitive way to identify a faulty crank PS or cam PS.
Diagnostics on page two of following:
viewtopic.php?f=29&t=59479