[themustangkid]

i have a seemingly bizarre situation with my engine. it starts great and idles just fine in park or neutral without shaking or rough spots and is fairly quiet due to a recent valve adjustment. when it is warm the car drives just fine and accelerates great and isnt lacking in power at all, however, when i pull up to a red light with my foot on the brake, it starts shaking fairly violently and will occasionally stall if it is also still cold. this problem is easily remedied by popping it into neutral to raise the rpm a bit. what the heck is wrong?

 

[brodieb]

Sounds to me like your stall converter is bad. Lets see what someone else thinks....

 

[Champion Speed]

How was it before the valve adjustment?

 

[rex1965]

Try adjusting your idle mixture screws, I always turn them in until the engine starts to slow down and load up (gets rough), then back them out until it smooths out and usually speeds up a little, then back it out an additional 1/4 turn, also make sure your idle speed is set properly, I think auto trans are 500 rpm in drive, you may may a dashpot on the carb, this is to slow the throttle, when you let off the gas, to keep from stalling or killing the motor, this one you have to put the car in park, and accelerator the throttle and let off and see how fast the engine returns to idle, it should just slow it down maybe a second or two. Why did it need a valve adjustment? Good Luck.

 

[bhmarx289]

My old housemate had the same issue you describe - he had a 68, 302 with a C4. Both an Edelbrock Performer and a Holley carb would do the same thing. Car would run/idle great, accelerated great, but would load up and try to stall when at a stop while in Drive. The issue was a tuning one with the carb, but I don't recall exactly what needed tweaking as he resolved it after I moved out.

I would start with the idle mixture as suggested by rex1965.

 

[themustangkid]

so here is a little more on the valve adjustment: i adjusted the valves several months ago, but developed a very loud ticking on the passenger side, so i re-adjusted only that side, and the engine became much quieter and smoother when idling in park. it still shakes about the same in drive.

also, the carburetor was very recently rebuilt by pony carburetors, so i dont think that the idle mixture screws would be out of whack, but ill try that just to be sure.
Thanks guys!

 

[themustangkid]

Winner of the day is rex1965!
After some tweaking around, i found that the idle speed was low. i got a tach and fixed that issue, and now it runs great while idling. :bigthumbsup
thanks a bunch for all of the advice guys!