Honda Car Forum

just happened suddenly, works fine if i dont go over 4000 rpms

There could be a million things that is causing that....you need to explain the problem more if you want it answered on here....

to me,4000 rpm is very high,and i suggest should be avoided

If by 'shake' you mean that the tachometer needle starts to bounce then the problem is a high speed breakdown of the ignition coil. when an ignition coil starts to break down it doesn't generate enough voltage in the primary windings in the time allowed between firing of the spark plugs. as engine speed increases the time to develop the voltage to fire the plugs is decreased. So if the coil doesn't recover and build up enough voltage to fire the plugs you wind up with a high speed misfire that causes the tachometer needle to bounce.the reason the tach needle bounces is that the tach signal comes from the coil. the tach is actually counting the number of times the spark plugs are fired to calcualte the engine speed. so if the coil is failing it will be reflected in the tach. Replacing the igntiion coil is the fix for that problemthere is only one other common thing that will cause your symptom and that is if you're hitting the rev limiter on the engine. that usually doesn't happen until over 5500 rpm when the powertrain control module will cut the ignition so that you don't go over the redline and damage the engine.if its occurs in the 4000 range you're not on the rev limiterhope that helps.