PREDATOR-Z

I've been guetting car hickups on deceleration from 45>30 mph.
Any ideas what it could be??

Bad IAT sensor?
Bad MAP sensor?
other??


Thanks

samz28

are you talking bout say locked up at 45-30mph(unlocked) slight driveline lash surging? or something else.

bad tune comes to mind. It takes alot of time to perfect the 0% TPS surging, i just found a way around it for now till the tuner man can work on it.

you sure you're not misifiring or anything causing the verter to lock/unlock?

hows it feel on a flat ground with no throttle? like cruise control or surging/driveline lash?

PREDATOR-Z

I used to have it but less pronounced with the stock TC. At cruise or acceleration, no issues. It only happens when i'm decelerating with no throttle, difficult to explain but like hickups. Normal, short jerk, normal, short jerk, normal, short jerk, and on... If I apply the brakes, I cannot feel it as much but I think its there. And that is only between 45 down to 30 or so.

samz28

yeah that sounds like a tuning issue, whats a GMAF?

samz28

keep raising your in gear idle after you add a few degrees of timing to base spark @ throttle closed.

I found -5 timing (factory) would increase bucking.
restored to factory
raised in gear idle a tad.
problem solved other than the cruise control but its not that bad actually since i can cruise to work 5 over the speed limit with no thoughts (or gas pedal action).

PREDATOR-Z

GMAF= Granatelli Mass Air Flow
I'll try that, I let u know tomorow.
Thanks.

samz28

yeah just set it to something stupid like 1200-1300rpm at idle.

mind you i drilled my TB which i probably shouldn't have.

It's probably a fault in my VE table thats the root cause but i've been too busy to go playing around with it and all so i ghetto patched it.

even when i'm locked in 4th at 35mph downhill theres 0 surging at 0% tps, then if it goes flat/uphill it will unlock at < 35mph.

I have to drive ALOT of city heavy traffic so my average mph is 30-40 so i'm gonna spend some time to get this right someday.

PREDATOR-Z

Set it a little higher (950) and the problem has diminished. I'll drive like that a couple of days for the pcm to learn and then i'll try a little higher.
Thanks.