Rough idle on the Mazda

Messages
383
Location
austin,tx
When I have the car in park you can feel it a little bit, but once in drive you can really feel it. The needle on the tach. doesnt fludder around or anything. When taking off the roughness will slowly fade away, until about 40mph then it starts up again pretty bad, until about 45-50 mph. It also starts if there is load on the engine, like when coming to a stop then accelerating before the transmission down shifts. So far I put in a bottle of techron, changed the spark plugs and wires, changed the air and fuel filters, cleaned the maf and throttle body. I'm not the sure what to look at next. Oh and no codes are being thrown.
 
Messages
17,869
Location
Silicon Valley
When my engine mount was bad, it was the idle in D that is really rough, and when there is load the roughness would disappear, it was also rpm instead of mph related. Can you check the ignition coil (resistance at room temp against a new one or number on the internet)? Maybe it is worn and the spark voltage is low?
 
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