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Matt
Matt, Mechanical Engineer
Category: Mazda
Satisfied Customers: 21867
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I've just bought an 03 mazda 6 sport. The problems I have

Customer Question

Hi I've just bought an 03 mazda 6 sport. The problems I have are that the car gets jerry and shudders along with the Rev counter going up and down like crazy. Seems to stop when I change gear. The check engine light and another light are on. Used a machine to check errors and came back with 2 and 2 pending. They are p0340 (cat not ready?) And u0121. Any ideas much appreciated as I can't afford to spend a fortune on repairs. Many thanks.
Submitted: 1 year ago.
Category: Mazda
Expert:  Shantal-Mod replied 1 year ago.
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Expert:  Matt replied 1 year ago.
Hellothis sounds like its misfiring ?So 1st replace the spark plugs if any of them fail this checklist:http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/faqread.asp You can also try spraying some water on the coil pack with the engine running. It is possible the coil is faulty and causing the misfire. If you see sparks arcing with the water, then replace the coil.I'd check the condition of the injector plugs / connections as this could be a lean misfire if an injector isn't firing properly - the best way to check this is with a 'noid' light http://www.noidlight.com/ Then check all the connections to the engine sensors one at a time, remove each one and examine for signs of corrosion or damage and a squirt of contact cleaner ( not WD40) will also help. This could be an airleak after the airflow meter, any air dragged in here isn't 'seen' by the ECU and so not compensated for and leans the engine out 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.Work your way through each possible joint one at a time and you should find it. I use a slightly flattened piece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements. It’s also worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a poorly pump will all result in insufficient fuel being delivered to the engine
Expert:  Matt replied 1 year ago.
Hido you still need help?Bear in mind that the site takes a deposit from you at the beginning and this is held by the site until you rate my answer at which point the cash is split between the site and the expert. I am only paid for my work on this question if you rate my answer, using the star system at the top of the screen. Please do not forget! Thank you