So, three weeks ago I sank $700 into my 1987 2.5L Chrysler LeBaron to replace the distributor, logic module, and MAP sensor. This was because the car would start, but then stalled out immediately (i.e., would not hold idle). I was forced to take it to an unfamiliar mechanic because I was 100 miles away from home, and they identified the problem as one of fuel not getting to the engine. After ruling out the fuel pump, they made what turned out to be an unnecessary replacement of the distributor, before replacing the logic module (I got a used part for that) and the MAP sensor. This fixed the problem, and also restored the cruise control to working order (in retrospect, I wish I had mentioned the cruise control not working to them when I took it in - that probably would have clued them into the logic module and MAP sensor, rather than the distributor, and I could have saved myself $250).
Anyway, since having these repairs done, I have noticed a shake in the car that I don't recall noticing before this work was done. The shake is side-to-side, and occurs only when I am giving it gas to accelerate (i.e., not when I am accelerating by rolling down hill for example, only when I am actually giving it gas), and even then it only occurs within a range of speeds. The shake begins at about 28mph, gets more and more noticeable until it reaches a crescendo at about 40 mph, and then slowly tapers off until ceasing altogether at 52mph. If I take it up to 70 mph, and then have to slow down to say 53 mph, and then accelerate back to 70 mph, the car does not exhibit this shake, nor does it exhibit it whhile accelerating before reaching 28 mph, nor does it shake once it reaches a cruising speed within the 28mph - 52mph range.
So, first of all, what could be causing this? I first feared the automatic transmission, but the beginning and ending of the shake do not seem to match a shift in gears that I can hear. Because it happens on acceleration, I wondered if it might be something with the fuel injection system, like a fuel pump, which was partly what the mechanic I took it to last week was attempting to diagnose, which is why I wonder if this shake is related. I am also worried it could be an axle, or, as my friend suggested, a rotor. What do you all think?