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Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 22764
Experience:  BEng hons Mech engineering, in auto industry 22 years
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have a problem with my mazda rx8 48000m 06 plate eml flashes

Customer Question

have a problem with my mazda rx8 48000m 06 plate eml flashes at 4000 revs have had new plugs coils and leads put on also new cat and front lamba censor had compression test done at mazda garage at 250 rpm front 6.4 6.5 6.6 rear 6.8 6.7 6.7 also carried out check on power train passed ok fault code po302 car drives great no lack of power
Submitted: 5 years ago.
Category: Car
Expert:  Matt replied 5 years ago.

code PO302 = rear rotor misfire.

So as you 've replaced a fair bit already I'd look into checking over the rear exhasut for exhaust leaks before the O2 sensor as if this has been experiencing an exhaust leak then it will have been running very rich as the sensor will see the extra air pulled in as fresh / lean fuelling and be adding fuel to compensate.

this can lead to catalyst failure as the extra fuel can re-light inside and melt the catalyst

The best way to find an exhaust leak is to run the engine from cold and feel around the exhaust joints with your bare hands - you'll have about 30 seconds before it all gets too hot and you should feel any escaping gas blowing over your fingers

I'd also check for a air leak at the mass airflow meter -
Any air dragged after the meter isn't 'seen' by the ECU and so not compensated for, causing rough running.
Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts.
The best way to locate a leak is to have the engine running and warm and then spray lighter gas around each joint in turn. If the engine rev's up you've found your leak.

Customer: replied 5 years ago.

have passed your answer to my mechanic he is going to check this out i forgot to mention the front lamba censor is showing 2.5 volts all the time it is not switching he says shold be between 0.05 and 0.95 is this correct

Expert:  Matt replied 5 years ago.
Hello Gary

that is correct, with the engine running and everything warmed up it should move between those values

a static reading of 2.5volts sounds like the sensor is either faulty or the wiring to it is damaged