Hey guys...finally got my '86 5.0 running well, but now I have a new problem. The tranny seems to shift fine when accelerating, but when I let off the gas (at pretty much any speed) the car seems to jerk or buck back and forth a little bit. Only does it for a couple seconds and then smoothes out. It does it in both Drive and Overdrive. I checked my kickdown cable on the throttle body and it's attached and secure. Anybody heard of this before? Is my tranny going out?
Well, according to Eric's web site a small amount of that "bucking" is normal in these cars, but I'd check the drive shaft and U-joints first if it's really that abnormal. Make sure the joints are nice and tight, and your drive shaft is properly attached.
As a side note, I had my U-joints replaced but there's still a little clunking when I let off the throttle :dunno: Oh well.
My 3.8L does something similar. I have a sneaking suspicion it's the EGR vent solenoid. As I let off the gas suddenly, the car bucks. If I let off the gas very slowly, there is no bucking. As the mass flow rate of the engine rapidly decreases, the vent solenoid cannot vent quick enough and the excess vacuum on the EGR causes too much exhaust gas to enter the engine. If the bucking occurs on a cold engine, it isn't the EGR. EGR isn't active until the car achieves closed loop. You can also disconnect the EGR line and plug it to see if that eliminates the bucking.
Both are good suggestions. Might I also add The possibility of a smog system problem, specifically the diverter valve may be sticking. I would definately check the other items listed above FIRST and then if problems persist check your diveter valve.