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Matt
Matt, Mechanical Engineer
Category: Mazda
Satisfied Customers: 22157
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I have a mx3 v6 1800 can't get it through mot keeps failing

Customer Question

Hi I have a mx3 v6 1800 can't get it through mot keeps failing on emissions what can be done changed oil/filter plugs air filter Prv valve what can I do to get it through if I change cat and exhaust valve will this make a difference thanks
Submitted: 17 days ago.
Category: Mazda
Expert:  Matt replied 16 days ago.

hello

can you tell me what emissions readings you were getting?

as it should be printed on the MOT ticket

if the hydrocarbons are high then it could be incorrect fuelling due to a faulty water temp sensor. If this is the problem then the ECU will be leaving the car constantly ' on choke' and not reducing the fuelling as the engine warms - so unplug the sensor and clean the contacts on both sides with some switch / electrical cleaner (not WD40) and inspect the wiring for any signs of damage to the insulation especially where it runs over other components and through the bulkhead- if this doesn't help consider replacing the sensor as they're not expensive

also check 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

if thats ok then try some of this:

http://www.cataclean.com/

Expert:  Matt replied 7 days ago.

Hi
do you still need help?
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