I have a suspicion that my recent manifold/throttle swap has caused my recent driveability issues. After the swap, my idle MAP reading rose to around 35-40kpa from 25-30. Additionally, my MAP seems to be weaker in general. Cruise hovers now in the 65-80kpa range and i have little to no difference between 35% TPS (95kpa approx) and 100% TPS (99kpa) which doesn't help part throttle/cruise at all. I didn't think that a 5mm increase in throttle size and a better distributing manifold would cause such issues. The engine is a 3.0L v6 running an MS-II, EDIS-6 that I had running well before the original body died. Does this seem reasonable or is there another variable that I might be missing?
Here are the two manifolds prior to swap. The upper is the "old" manifold and the lower is the "new" manifold off a 3.5L variant of the same engine.
if all that you changed was the manifold and throttle body, your map should have stayed pretty close to the same, unless you have a intake manifold leak, or the throttle body idle screw might be open too far, a 5mm change in throttle body size shouldn't make a large difference in idle and cruising map unless vacuum port is possibly leaking. check all the sealing area's in the manifold. its probably something really simple. Good luck
Kaeman - Thanks for getting my head on straight. I started working through what would be causing a "vacuum leak". While I didn't find any physical leaks, I did find that my adaptive idle settings were configured so that my IAC was NOT closing once I started driving. Having my IAC halfway open sure affected my MAP readings! Now that the IAC closes once the car is driving, the readings are more sane. Not as low as with the smaller TB/more restrictive manifold, but the vacuum loss is more acceptable to a TB/manifold swap. Plus the driveability is way more manageable again.
