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Matt
Matt, Mechanical Engineer
Category: UK Car
Satisfied Customers: 20598
Experience:  BEng hons Mech engineering, in auto industry 22 years
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Mazda CX-7 Touring: - I have a Mazda CX7 petrol. When driving

Customer Question

Hi - I have a Mazda CX7 petrol. When driving between 20-30mph in second or 3rd gear, the car start to vibrate heavily (almost like an old bus), sounding as if its in 5th or 6th gear. Usually okay if I am accelerating quickly through those speeds, just a problem when the speed is maintained at that speed.
Submitted: 1 year ago.
Category: UK Car
Expert:  Matt replied 1 year ago.
Hello 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.
hi do you still need help