My truck after getting a built tranny, stall, 410s, and retuned would surge only in reverse. While backing up and letting off the gas would act like it was going to die. And jump from about 400 to 1000 rpms but then idle perfect when put in drive... I just kinda delt with the issue, but now it's doing it in drive when comic to a stop occasionally now. What do y'all think is causing this??

 

Tune issue..

 

I sure hope not. Getting ahold of Wheatley is a act of congress. Anything else to check or do? Don't These engines have a idle air control valve..

 

It sounds like you need to increase your desired airflow in gear. Wheatley has been busy, but has gotten back to me quickly. Do you have tuning software? in EFI Live it is {B4307} just increase that a little bit, and it should help. There is also a throttle cracker adjustment, and that is in effect when you are above about 5 MPH.

 

I went out and bought hptuners just for this truck and to adjust tire size for the track and daily use, just to find out my PCM was locked. It does the surging under 5 mph mainly when I'm stopped or damn near. It's extremely irritating and can't be good on my truck.

 

Wanna sale the hp tuners?

 

Have you drilled the hole in your throttle body at all?

Allen Nelson suggests enlarging the hole for large cams, so the IAC doesn't have to cycle as much.

Obviously try to work it out in the tune first, but if that fails, this is something else you could try.

 

You could ask your tuner to unlock it for you. Or get them to correct it.

 

The throttle follower decay needs to be increased a little. When throttle follower is active, the idle trims are inactive. If you get follower to decay to zero faster then the Idle trims take over and it will stop doing that. Unfortunately you would have to have access to the PCM to do that.