Odd engine shake when rad fan is on.

[Godofwarmike]

Ok so in my last post my engine was shaking all the time and the check engine was flashing.

Well new coolant temp sensor fixed some of the shaking and the flashing check engine light.

A new front motor mount fixed the rest of the shaking but....

when the radiator fan kicks on the engine dies down and shakes quite bad till the radiator fan kicks off.

any ideas?

also not sure if its related but if i use the stock wiring for a radio the radio reads failure (Sony Xplod) but I put it in a different car and it works fine.

and once in awhile my turn signals dont work unless I give the steering wheel a few good wacks

126,000 miles
1999 Plymouth Neon
SOHC Automatic

[denisond3]

The load the radiator fan puts on the alternator will involve a slight change in engine speed, maybe too small to cause the IACV to compensate for it; so some of that shaking may be inevitable. With our Neon, I normally put it in neutral when sitting at a traffic light - and there is less vibration. My wife however, never bothers to do that.
Also look for any vacuum leaks, like a bad PCV hose or other vacuum lines. The slower the engine is running the more a vacuum leak will disrupt its idle.
A dirty throttle body can cause rough idling. To clean it you might get away with spraying 'throttle body cleaner' into the inlet where the butterfly valve is, but unbolting it and cleaning out the muck behind the valve would be a better solution. Crud that accumulates right behind the throttle valve will disrupt running at the slowest rpm - doesnt have any affect when driving.