Idle Timing/RPM Drop in Drive

[BizarreCustoms]

The vehicle is a 2000 Yukon 2wd 4L60e with traditional cable throttle. The 4.8L was swapped with a refreshed 5.3L. As far as power adders, it got a cold air intake (which was on the car before the swap), long tube headers, and a compcams camshaft with maching springs. The cam specs are:

Duration @ .050" In 222 Ex 224
Lobe lift In .333 Ex .334
Lobe separation 112

All other elements are stock off the truck including intake manifold, throttle body, and injectors.
I am utilizing the 4.8L computer for the swap. I have set it to a 5.3L and updated the displacement.
I have disabled EGR and removed all DTC's for EGR and down stream O2 as well as updated the idle bas SETpoints, Idle Airflow, and added a little bit of timing. I have the truck at a point that it will crank over with no throttle interaction and idle fine regardless of engine coolant temp. I can also snap the throttle hard and it revs fine and returns to idle fine.
The problem I am having comes when I drop it into drive. It did not do this before the 4.8L was swapped out. When I put it in to drive, RPM drops to around 300-400 (low enough to not produce oil psi). From what I can see while logging it is ignoring my base and idle timing charts and pulling all the timing out. It also feels like it is loading up the engine but fuel trims do not reflect. If I start driving it seems fine once above an idle. I have played around with just about anything I can think of try and resolve the problem with no luck. If I change the max spark retard table I can force it to hold timing/rpm but the engine still feels like its fighting and loading up. I know this isn't a repair but verified my thought that the computer is retarding the timing for some reason and has been returned to what it is stock. When I compare current file to my stock file I don't see anything that i have changed that should affect this. Any help resolving this would be great.


uploaded a video of what it is doing to youtube.
https://youtu.be/GYwZHWvZ2cI

Stock53_2wd4l60_Drew Replica RTT4_4.hpt
drew5_3 InGear Idle Issue.hpl

[anniversaryss]

Try turning off brake torque management first.

Under system > system options > brake tqmgt make the 1 a 0 and see if it still occurs

[BizarreCustoms]

Try turning off brake torque management first.

Under system > system options > brake tqmgt make the 1 a 0 and see if it still occurs

Just tried, still doing same thing.

[kevin87turbot]

As a quick test, you can always adjust the min spark table to a reasonable timing value at low rpm...maybe around 16-18 degrees at idle, and see if that stabilizes the idle.

[BizarreCustoms]

As a quick test, you can always adjust the min spark table to a reasonable timing value at low rpm...maybe around 16-18 degrees at idle, and see if that stabilizes the idle.

I have done that and it does work but it even though the rpm will stay up, it feels like it is still fighting itself.

[kevin87turbot]

It needs a lot more air as well. It's idling in Park at around 160 on the IAC counts. It needs to be around 60. I see that the TPS is around 0.69V. You can open it up a bit more...but you may have to drill a larger hole in the TB blade in order to accomplish this. Another option is to install an aftermarket TB that allows the min airflow to be adjusted independently from the TPS adjustment. I just went through this same issue on a 2000 Silverado with a 4.8 and a large cam. The aftermarket TB along with ICT TB adapter worked nicely.

[curiousg7]

The cam is gonna want a bit more air, and probs 16-18 deg of idle timing ish. If the TB was opened up, the IAC table will problly be off. However, you need to open it up more to get the counts down. I agree with kevin that a better adjustable TB is needed or maybe just a hole drilled. Then adjust IAC table and move on to other tables.

[BizarreCustoms]

It needs a lot more air as well. It's idling in Park at around 160 on the IAC counts. It needs to be around 60. I see that the TPS is around 0.69V. You can open it up a bit more...but you may have to drill a larger hole in the TB blade in order to accomplish this. Another option is to install an aftermarket TB that allows the min airflow to be adjusted independently from the TPS adjustment. I just went through this same issue on a 2000 Silverado with a 4.8 and a large cam. The aftermarket TB along with ICT TB adapter worked nicely.

The cam is gonna want a bit more air, and probs 16-18 deg of idle timing ish. If the TB was opened up, the IAC table will problly be off. However, you need to open it up more to get the counts down. I agree with kevin that a better adjustable TB is needed or maybe just a hole drilled. Then adjust IAC table and move on to other tables.

I didnt think to look at the IAC counts. I opened the hole up till I was around 35 in p/n but when I shift to park the IAC counts climb up and away and it pulls timing/rpm back down. I did notice that it seemed a bit happier than before if I locked timing at 19 degrees but not perfect. Se I tried to swap over my buddies larger t-body and it brought p/n idle IAC count down to 0 but then it still climbs up and stumbles out in drive. I did not change anything in the tune other than readjust the base running airflow. Attached new log from enlarged stock throttle body hole.



drew update hole in tbody.hpl

[kevin87turbot]

That looks much better. It needs more timing for sure. It's odd that it's dropping the timing in gear. Set the minimum timing table to Force it to at least 20 degrees at idle, then see if the fuel trim needs adjusting.