I have a '91 Integra LS Automatic with 106,000 miles. It had plugs, spark plug wires, cap and rotor, valve adjustment at 90K, t-belt and water pump at 75K. It runs strong, but at idle in drive, it seems rough to me. It's not missing, just feels like you can feel every cylinder fire. It's smooth in Park, worse when the A/C compressor kicks in. The idle speed may be a little low, but it looks like it's about where it's always been on the dash tach (I know that's not the best way to check, but it's what I have). No check engine light (ever!). I also put in O2 sensor at 90K.

I've had this car since new and it used to idle smooth in gear with the A/C on, but in recent years, it's just gotten rougher. Any clues or ideas? Thanks in advance!

 

i got a 91 ls 5 speed it idles real low when the AC turns on and it idles rough then too. chack your fuel filter maybe run a bottle of fuel system cleaner in it with full tank of gas. clean your throttle body too.