I've searched, but maybe in the wrong place. . .The good news, my car is running as well as it has in years! Now I'm tackling little annoying things. When I go from mild acceleration to neutral throttle, I get this little herky-jerky (bucking?) in the car. I don't think it is mechanical. Doesn't do it under acceleration or deceleration, only neutral throttle -- like it's firing a little uneven there or something. The exahaust also seems to "pop" more at this neutral setting. Recently had a Steve Kan tune, but could it just be a little rich at this vacuum/rpm range? I plan to experiment, but thought maybe others had tackled this before. Thanks for any advice.
--Jeff

 

You did not say if it happens at all speeds or only at specific speeds.

Tuning has to be precise to be good, and you have to be precise.

 

It happens more at moderate speeds, 20-30 mph, and going from moderate/light load to neutral load. I did notice it on the freeway the other night however with cruise control on when it went from light load to neutral load at about 70 mph. I'd say always in vacuum (as opposed to boost) and around 2500 -3000 rpm. That is where I was going to try and log and see what I can find. Was just hoping that maybe this is not too uncommon. Thanks.

 

Sounds like it is too lean when off load.
AFR tuning for cruise is the most difficult to do.

Based on my car:
(1) At speeds below 60mph, I need to run progressively richer as the speed drops.
From an idle AFR of about 13 my AFR slowly leans until about 16 AFR at about 55mph.
(2) Above 55mph, I can run 16.5 - 17 AFR no problem.
(3) At the point where the secondary throttle starts to open, the AFR tends to lean out due to the change of air flow into the chamber. This requires this point to be slightly richer.
(4) Fuel cells above the cruise cell should be the same AFR as the cruise cell.
The first cell below the cruise cell should also have the same AFR. Futher cells below this are acceleration cells and need to be rich.

Note: Most idle AFRs will be richer due to most people run stock timing there due to the ISC idle control.
Without ISC idle control, you can increase idle timing for more efficient idle use of fuel.

 

Thanks. That may make sense in that Steve had it just a little too lean at idle as well. I was confused because I thought maybe it was rich as I'm getting more exhaust "popping" at that same "neutral" throttle than I used to. I don't worry as much about playing around with these "non blowing your engine" areas of the map so I'll experiment. As you get closer to optimum settings, it's amazing how much a little adjustment here or there can do to the smoothness and drivability of these cars!
Hmm. Also, it just dawned on me that he tuned it with the air pump disconnected (which I know is the correct way), but when it kicks on at (2500 rpm with PFC?) it could be leaning out more. . .

 

Most owners do not think logically about tuning. They only think about power tuning.

BUT your engine spends most of it's time cruising and idling. That is where you can save gas, and want smooth driving.

Log the exact bad spots to see exactly what is happening.