2nd owner, 1987 Accord LX, auto, 2bbl, with 102K miles in otherwise excellent condition and regularly serviced. Recent new plugs, wires, cap, rotor, air filter and pcv valve. Carb appears clean. Compression good and vehicle runs very well. However, at stop lights with trans in D, it idles rough with noticable shaking (A/C on/off does not affect problem). When shifted into neutral, idle smooths out and shaking stops. When put back into D before starting out, noticable "thump". Any idea what the problem is? Perhaps a bad rear motor mount? Where and how is that checked?

 

For the THUMP, you ought to check the engine mounts. Grab the valvecover & shake the engine around.

Next, watch the tachometer when you shift from neutral into drive or reverse. What's idle RPM in each gear? There's some kind of idle-air valve that's SUPPOSED to add air to maintain idle RPM when it's in gear. Maybe that's not working right; needs adjustment? I don't know that carburator very well, so hope someone chimes in.

Then finally.... A couple years later, Honda began using a vacuum-operated rear engine mount. That thing is switched on & off so it gets SOFT when the engine is idling in gear. So maybe this is just the way it is for 1987.

 

sounds like a collapsed rear mount.......

once engine is warmed up, at idle,, raise the car up, car in neutral have a friend inside the car
,from under the car,, use a paper clip .. put it in the middle gap of the rear mount, have your friend shift car into drive , if paper clip does not pull out easily rear mount is collapsed.. ..

 

J and D: Thanks for the tips guys. I'll do the MM check (assuming I can find it) before playing with the carb.

Ron