Engine vibration at low rpms engine has a vibration. as soon as rpms go up the car runs good. a mechanic said it's not a miss it's a vibration. he checked the wires & plugs & harmonic balancer.

There could be a lot of possibilities. Does the engine make any type of noise? how high was the RPMs when it happened? Was the engine under a heave load? I was pulling a load of hay into Kingman Az and was in second gear when my engine did the same thing. Too high of RPMs and bent a valve. First do a cylinder balance to find out if you have an engine miss. Check the missing cylinder by looking at the spark plug. Check compression.

Run a scanner to see if you have an engine miss fire under load. Bad injectors could do that.

first off have you had the fault codes read
that will give you an indication of any electronic fault
I consider the problem is misfire but not from the coil packs but from bad injectors I would at this stage discount a problem torque converter as if there were missing /broken vanes the you would have more than a vibration and besides that oil or fluid has a capability of balancing out any unbalance ( laws of physics)
idling too low ( around 950 rpms for auto) may be a problem or the harmonic balancer could be failing
bad engine mounts could be allowing excessive engine movement especially on take off but if bad enough the engine mount which is a rubber insulator may be allowing the steel section to be vibrating metal on metal
So , have the fault codes read first
then check / replace any mount that is not up to new standard

could be a spark plug or plug boot, depending on the last time they were replace i would recommend replacing them all.

Had the same problem. In my case, the wiring harness was scraping against the vibrating motor and wore through the insulation. This caused the computer to think the throttle position sensor was bad and the RPMs were erratic. The engine light came on and indicated TPS. A short time later, more of the wires became damaged and the engine started missing cylinders. My problem was at the top rear of the engine where the harness runs over a metal stud (right behind the valve cover). Check your wiring harness. Not an easy find until you actually look for it specifically.

Dodge Dakota misses at low rmps but not at higher rpms, what gives?

could be new engine mounts or miss fire ...

bad engine mount make car shake.cylinder misfire make engine shake.

Hi,

vibrations over 55 mph are usually balance related (tire balance, drive shaft balance, motors)

vibrations at lower speeds are usually mechanical (bent rims, out of round tires, bad tie rods)
Therefore the suggestion for checking the harmonic balancer is perfect in your case.

Thanks