Does a loose rocker arm cause it to idle rough?? As of right now my jeep grand cherokee 4.0 ildles rough. Pretty much done all the basic tune ups but still have the problem. When I start it up there is a slight tapping noise coming from the vavle cover....could it be a loose rocker arm cause this rough idle???? Thanks in advance

 

NOT confirming that your issue is a loose rocker
But yes a loose rocker will affect the idle. So will a vacuum line.

Ron

 

Yes, a loose rocker can cause a miss.

 

Agreed, but the rocker arms on the 4.0L aren't adjustable. Could be a valve train problem, or a worn camshaft.

 

A bad lifter that isnt pumping up will do this also

 

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