Losing power
I have a 2006 Mazda RX-8 192HP with 99,000 kilometres. It was running as sweet as a nut until two weeks ago on a 50-mile run, when it suddenly lost power as if running on one rotor. After dropping down to 5mph in first gear, it died and would not restart, but in the morning it started first time. I decided to take it for a spin and it started losing power again after 10-12 miles. In the morning it started first time and revved freely.
I am pretty sure it is not a compression problem as it had given no signs of this before now, always started hot or cold and pulled well in all gears. Having fitted new plugs, coils and leads, I suspect the problem is a blocked cat. When I took a look, I found the insides had already been knocked out – they do that here in Ireland, as there is no emissions test on these cars – and it had obviously been running fine without it. No warning lights have come on, so there are no codes to read.
I can’t understand how can run fine for 10-12 miles, then lose power and stop. Then, when it has cooled down, it starts again. I suspect it might be a crank angle sensor breaking down when hot – if that is the case, can I just remove the old one and do a straight swap or do I have to set any timing before replacing the sensor? Chris Barrett
Even though you do not suspect compression problems, I think your first move should be to get a compression test carried out when the engine is hot. This will clarify the situation and allow you to move on with the diagnosis. There is information on this subject on the RX-8 owner’s club website at http://bit.ly/1wsrj4f
With the symptoms you have experienced, if the crank sensor were at fault I would have expected a code to be flagged up. If you wish to change the crank sensor, it simply fits in place and no adjustments or checks to the timing are required. I would also check the vehicle’s data using a scanner to ensure that the air and coolant sensors are giving the correct readings. These engines are also known to use a small amount of oil and the level should be checked to ensure it is not low.