Bad high stall TCC or tuning related?

[turabo87]

Hi,

I'm having difficulty getting an Fbody to maintain idle after going in gear (reverse) from Park/Neutral. It's an 2002 with a 4.8L swap, BTR Stage 4 Truck cam, with a TCI 3600 stall (PN 242932), and a 3.73 rear end. I don't have much experience dealing with aftermarket TC or TC settings in general. After conversations with TCI over the TC behavior, I'm believing that either the TC is defective OR there is a clutch lock up setting I've overlooked.

Some background: The car previously had a massive vacuum leak coming from the brake booster. Before finding this vacuum leak, I was actually able to achieve a 950RPM P/N idle and an 800RPM In-Gear idle with some less than ideal tuning trickery. Leaning the AFR significantly and retarded timing and I was able to get it to idle despite large amounts of airflow in idle. Interestingly, this amount of airflow was actually aiding in providing the necessary torque to overcome the TC load in gear. That's when I noticed that the TC was VERY tight and creeps forward aggressively even at 800RPM, and unless you have the brakes firm it will creep forward with serious torque. TCI confirmed it's not normal for their 3600 stall to creep like this and be so tight in idle with my combination.

So, after the vacuum leak was fixed I obviously needed to redo the idle the correct way. That's when I found that once the idle at P/N was set an a near stoich AFR and adequate timing (20-22), there wasn't enough engine torque to overcome the load of the TC in Reverse and would shut off. I've already tried increasing base running airflow, I've manually tested the IAC operation with special functions and it works, but even at DOUBLING base running airflow and having it idle a near 2k RPM, as soon as it goes into gear it still stalls.

At this point I'd like to explore TCC settings, and perhaps I left something out and maybe the TCC is engaging. I've raised the TCC lock up speeds on all gears to 255, so not sure what else could be causing this or how to troubleshoot the TC and TCC any further before concluding that the TC might be faulty. Any recommendations are welcome, since I'm pulling my hair with this vehicle and I'm going in circles. Thanks.

FYI: Video shows when vehicle had the massive vacuum leak, which actually aided in airflow to generate the torque to move the car and overcome the load of the TC. Idling at about 800RPM in gear in the video.
Also, vehicle has FIC Denso 36lbs injector and all injector data is 100% correct and doublechecked. Vehicle being tuned in OL. Tune file attached with 2 reference files. Ignore the retarded idle timing; it was an effort to lower idle RPM while maintaining high airflow.

Danny Firebird New ECU Calvo Tune.hpt
2002 Silverado 4.8 Stock Tune.hpt
2002 Firebird LS1 auto stock tune.hpt

[turabo87]

Can someone please review my tune for TCC settings to see if maybe there's something TCC related that could be causing this tight torque converter behavior in gear in idle?

[kevin87turbot]

I looked at the Danny Firebird tune. In it, you have the TCC completely disabled. The transmission will not hydraulically lock the TCC in 1st or Reverse, regardless of your TCC calibration. If the TCC is dragging, then it's because of a mechanical issue. I have seen a few applications where the torque converter bolts were too long, and that caused a mechanical binding of the TCC. The bolts had distorted the clutch surface of the converter to the point that the TCC was always bound/dragging.

As far as your tune, I'd recommend disabling Abuse Mode on both the engine TM as well as the transmission Abuse Mode. I also noticed that you have a very large diameter tire entered into the tire/gear wizard. Did you do that on purpose?

[turabo87]

Well, we fixed the issue, or should I say the customer fixed the issue. Came back next day to his house and I hear the car chopping away at idle perfectly and also maintaining idle in gear and a huge smile on their faces. The problem was incorrect PCV hose routing. It was previously routing all the PCV back to the throttle body and we believe it was basically suffocating the intake with exhaust gases and not aiding in generating vacuum. It actually idled perfectly now and very strong and stable with 13 deg and a healthy vacuum of around 60kpa. Engine is now dialed in. IAC is also now in the operational zone. Pics below of before and after that caused the fix.

Before: IMG_5671.jpg After: IMG_5664.jpg

About the tire/gear wizard, I didn't use the wizard instead I did the math conversion from going from 3.23 gears to 3.73, but I think I did the conversion wrong in the opposite direction because the speedo was marking about 45mph when we were doing 33mph GPS verified. I think I'll use the tire/gear wizard next time; the tranny is still pending a tune another day.

PS: I still think the torque converter is a little funny. It's very tight in idle an creeps forward/backward without throttle much like a stock converter. Doesn't act much like a high stall in idle but they're moving forward with it as is.