When I'm sitting at a stop and the car is in drive, there is an intermittent bump (best word I can think of) in the idle. It is also reflected in the tach. Happens warm or cold. The car idles fine if in park or neutral.
Any Ideas? Is this a symptom of woes to come? Thanks!

 

MJS,

We'll throw a thought or two out and see if you can check them out.
There is a difference in where the engine sits in park or neutral compared to drive. If there was a defective or worn motor mount(s) that could move wires and components attached to those wires. It might be a good idea to check the mounts, and also see what wires move. Certain wires providing power or ground can open with engine movement or even rub against sharp or hot surfaces and rub through making intermittent contact. This is only an off the wall theory, but might be a good idea to check out.

The crank sensor sends its signal on to the ign system and momentary loss of signal can feel like a bump. Also, the tach signal is a clue ignition is intermittent. So I would start looking at the crank sensor wires and look for anything unusual there.