Idle falls when put into drive. Not sure what to do.

[SiskMan]

I am tuning a friends 2000 sierra with a sloppy stage 2 cam and a 6.0/4L80e swap. Originally a 4.3 truck. Idles great in park and drives really goodm aside from this problem. But when you put the truck in drive, or come to a stop, the idle will fall to 300 or so. It wont die for a little while, but will eventually. No bucking, no surging, just stays around 300 rpm. Reverse, and 2nd gear at a stop are fine. It did this with the 4L60e as well. Truck has a 4.8 stock stall in it now. I have it idling great at 700 in park.

Note: i do think there is an exhaust leak or a bad O2. Forced the truck in open loop mode and its the same thing.

No other automatic vehicle that i have tuned has done this before. My auto trans am didnt do this. A tahoe i tuned a couple weeks ago didnt do this.

Sorry if i didnt log all the necessary PIDs to help figure this out. Tell me what to log and i can get it done.

Any ideas?

idle log.hpl

6.0 Running Tune WITH 4L80E SEGMENT TRY THIS messing with idle adding MAF.hpt

[Dan_W]

Sounds like you need to tune your BRAF. There are different values for P/N and Gear.

Try this guide:
https://forum.hptuners.com/showthrea...e+tuning+guide

[1364838952]

2 things come to mind here... What is the history of the 80E? These units-after high mileage, tend to wear the pressure control valve in the pump which then allows the torque converter clutch to drag when idling in D, or R.. This will sometimes cause the engine to stall when sitting at a red light, or when trying to back out of a parking space and turning the wheel hard in either direction. When coming to a stop, if you bump it into neutral will it idle PERFECTLY...? Or will it hunt, and stumble even for a short period before settling into a good idle? If it still hunts/stumbles/struggles to idle even in neutral-it's in the tune! If it idles perfectly when you bump it into neutral, it *could* be trans related. You can try bumping the in-gear idle up a little bit to band-aid the problem if it is in the trans. There are mods you can make to the trans to fix this issue without having to drop the trans. You also did not say whether or not he has put in a stall converter???? That cam is NOT going to be happy idling a motor tied to a stock torque converter/4L80E trans.

I would strongly suggest that you have some work to do on the RAF table. That cam is going to require some careful tuning of RAF. I'm running the cam just under the Sloppy Mechanics and it took quite a while to get the engine to idle at 675 with a nice lope. I had to open the set screw on my TB to get my IAC counts down, and then very careful tuning of the spark over-speed/under speed, and RAF, and EOIT adjustments.

**Dan W posted while I was typing! Great minds think a like.

[SiskMan]

2 things come to mind here... What is the history of the 80E? These units-after high mileage, tend to wear the pressure control valve in the pump which then allows the torque converter clutch to drag when idling in D, or R.. This will sometimes cause the engine to stall when sitting at a red light, or when trying to back out of a parking space and turning the wheel hard in either direction. When coming to a stop, if you bump it into neutral will it idle PERFECTLY...? Or will it hunt, and stumble even for a short period before settling into a good idle? If it still hunts/stumbles/struggles to idle even in neutral-it's in the tune! If it idles perfectly when you bump it into neutral, it *could* be trans related. You can try bumping the in-gear idle up a little bit to band-aid the problem if it is in the trans. There are mods you can make to the trans to fix this issue without having to drop the trans. You also did not say whether or not he has put in a stall converter???? That cam is NOT going to be happy idling a motor tied to a stock torque converter/4L80E trans.

I would strongly suggest that you have some work to do on the RAF table. That cam is going to require some careful tuning of RAF. I'm running the cam just under the Sloppy Mechanics and it took quite a while to get the engine to idle at 675 with a nice lope. I had to open the set screw on my TB to get my IAC counts down, and then very careful tuning of the spark over-speed/under speed, and RAF, and EOIT adjustments.

**Dan W posted while I was typing! Great minds think a like.

Yes the truck idles like a kitten as soon as you put in in park or neutral. Fires up instantly every time. 2nd gear is fine, but drive, first, and sometimes reverse it will just hang at 300-400 and eventually die after about 30 seconds of chugging.

Yes stock 80e converter. No one ever listens to me to put a converter in before a cam lol. IAC counts were 60-70 last night when we messed with it again.

80e is a local rebuilt unit he says. Ill mention the pressure control valve. Thats very interesting.

Ive never had this much trouble getting a truck to idle in gear, and this is the first 80e truck ive tuned. So perhaps it is the trans. I tuned a 02 tahoe a few weeks back with a BTR stage 4 truck cam and stock converter and it idled fine at 700 with minimal effort and didnt push the converter much at all.

I used that guide posted above, but when it still wouldn't idle the tune got sloppy due to me changing so much and being frustrated i guess.

[Dan_W]

What is your iac position when this happens?