well i have had this problem for a while now but now it sems to have gotten worse when the car is in Park or Neutral it idles so smooth and i think it idles high but as soon as i drop it into gear it shakes really bad but when i let of the brake it accelerates so smooth and is pretty quick but i cannot figure out whats up with the massaging mustang cause its annoying and second its rattling my emblems off and i want it to drive smooth BTW my right bank exhaust sounds like someone is punching a pillow when idling i have 67 coupe 289/c-4

 

well i know it takes time but i need to know

 

Try 2 things.

1. New spark plugs
2. adjusting the 4 corner adjustments (mixture) on your carb

Mine idles at 900 in park and 750 in gear. Idles real rough and I started almost stalling all the time when I was at a dead stop (so much so that I had to kick it to nuetral to keep it running). I just put new plugs in and the old ones were gas fouled apparently from an small ignition problem I had that took me a while to get rid of. With the new plugs, it doesn't try to die at idle anymore with no other changes.

If you still stall, adjusting the mixture will help.

 

thats what i thought so i made it rich with no help then i leaded it and no help i was told that the msd box would make me go through plugs more but i took it out and it looked ok but maybe it is gas fouled i was thinking it was my torque converter maybe i should use platinum plugs

 

Sounds like you just need a general tune-up.

 

I would check for a vacuum leak. This could cause the symptoms you are having. Check all of the vacuum hoses and connections as well as the intake and carb gaskets. Spraying some carb cleaner around the edges of the intake and carb while the engine is running can help you locate a leak. This will cause the idle to speed up when you spray it where a leak is.

 

I've read that a 289 Mustang should idle around 800 RPM + or - 100 RPM, though I'm not sure if that is in gear or not.

 

My 71 302 does something like that. Idles nice in park then once you shift, the load is so much, it starts to stall, or does( if not warmed up) it or idle REALLY low.... -Jon

 

i have checked the manifold no leaks i need to check hoses and i will put plugs in enem though these plugs are only a couple months old any recomondations for plugs

 

yeah, mine usuall idles around 900, and drops to 600 when in gear. My car picks and chooses when it's going to run good.