Buck when slowing down

[tiremelters13]

Titles pretty self explanatory. 90' 240sx with a ka24e. When slowing down or even when downshifting car bucks rapidly. Car was sitting for a while initial thought its nasty clutch chatter. Any other ideas or opinions???

[Banegraphix]

had a old single cam that did that as well and it turned out to be a huge vacuum leak around the egr

[mhillard1]

Yes, a vacuum leak would be the most likely/common issue; and would be the best place to start! Next time you drive it, focus on the sound of the engine; if you hear the engine surging, or sputtering along with the car jumping, then it's clearly in the engine, and you can usually dismiss the suspension and drivetrain. If the clutch is going out, it can make matching rpm's while shifting a bitch, obviously disengaging a clutch will do that (if you've ever taught a girl how to drive standard, you already know this); HOWEVER it is not likely the clutch, because it will not affect your rev count when not engaged (depressed). I would start by cleaning the fuel tank with some Lucas and swap the fuel filter. If the problem persists, I would almost guarantee it's still in your fuel system (Bad pump, ruptured lines, clogged filter, or dirty injectors). I hope this helps.