Stalling after warm start

[onspeed]

Having an issue with a cammed '00 Formula. Can't recall exact cam specs off the top of my head but it's pretty mild. EPS 228/232, .60x/.60x 113 LSA I think, or similar. Car was tuned by a very well known shop in Houston, then a second time after I was having some driveability issues. Even after the second time I wasn't quite satisfied with the car, but didn't bother taking it back.

My main issue is with warm starts, mostly with the AC on. The car won't hold idle until it's been running for a couple minutes, meaning I have to start it with the AC off. Problem is most severe when the car is warm. Cold and hot isn't as drastic.

I've attached a log of the issue, the original tune they did, and what I'm experimenting with right now. Log is a few starts with AC on. Then at 40 seconds I turned off AC and started car. I don't have a wideband hooked up to this car, but I assume the VE and MAF tables were done properly. I messed with the throttle cracker a bit to fix a hanging idle issue when rolling, and I've been playing with the spark tables but whether I add or remove timing advance it doesn't seem to help the issue much. I also removed some base idle airflow based on logging with adaptive idle disabled and letting the car warm up from cold.

I'm a little confused on how the under/overspeed spark correction works in relation to the idle spark tables. From what I can tell, the idle spark tables gives the maximum amount of timing the PCM will give. So if my logs are showing that the spark advance when the car is trying to recover the idle is matching the value on the table, does that mean I should increase the table to give the spark correction more room to work with? And I usually read that my main spark table should match my idle spark table, but I'm wondering why the shop didn't do so.



b-idlefix2.hpt B-original.hpt idle.hpl Idle-Airflow.cfg

[onspeed]

I have no issues with AC off. When the idle starts oscillating like around frame 700, it'll resume normal idle as soon as the AC is switched off. So I'm assuming it's one of the idle ac modifiers? I also noticed just sitting at a redlight, it starts oscillating sometimes.

[onspeed]

Any ideas on this? I've changed a few things here and there to no avail. I'm wondering if the oscillation at idle is associated with the AC compressor automatically switching on/off to prevent icing on the evaporator?

edit - Logged AC pressure. No change when oscillation starts. I just don't understand why it's start out of the blue.

after comparing the VE tables with a stock 2000 formula tune, I just realized the shop only changed 400-1200 RPM tables...

Is there something special with the F-Body PCM (versus a C5) that it doesn't reference VE tables above 1200 or did they just half-ass it? It's a very well known LS race shop in Houston. Hard to believe they would do that considering their reputation. Maybe the mild cam doesn't need PT adjustments? Either way, 1200+ tables shouldn't have any effect on idle I think?

[kewl_blades]

Looks like your tune was just edited a little to get it to idle and not much else.
Do these one at a time and see how each setting affects your issue.
1. Go and zero out the stall protect under Engine>Torque Management>Engine .
2. Up the Base Idle RPM for your AC ON under Engine>Idle>RPM. I personally add 100 RPM for when the AC is on.
3. Then, I would start by putting the Adaptive Idle Airflow back to stock (Engine>Idle>Airflow).

[onspeed]

Yeah I agree, looks like they did minimal changes. It was tuned before I got HPTuners, so I didn't know much except that the shop had excellent reputation on every LS forum. I tuned my C5 myself, and it runs great after working out 1 or 2 minor small problems. Unfortunately, I don't have a WBO2 on this car, and the PCM seems to operate slightly different than the DBW C5. 2 VE tables, IAC motor, and it seems like the adaptative over/underspeed tables don't do anything in the f-body?

edit - thinking i might have some fueling issues. with no WBO2 it's hard to tell for sure, but I'm getting a good amount of knock retard, 2 deg up to 9 sometimes, in places where my STFTs are within 5%. Even in PE i'm getting some retard. Maybe a clogged fuel filter. Loaded the original tune from the shop just to make sure it wasn't my modifications, and same thing. Timing doesn't look too extreme either, I think there's 2 deg adv ground into the cam. I can feel a power loss as it retards, never felt it before.

[onspeed]

AC compressor seized today. I assume it's been going downhill for a while and that was causing the random stalls at idle. This would also be the third time I'm replacing it, must not be flushing the lines enough.

As for the knock retard, I changed the fuel filter and there's no difference. I pulled up the only scan I could find for this car where I actually logged for knock retard, and even back in December I was getting KR. I guess I never actually looked at the data since I was assuming the shop did all the fueling and spark right.

Default Imperialv2.cfgknock retard.hpl Here's the log I took today shortly before my compressor seized. This is with the original tune from the shop. STFTs are all over the place. This is going on the back burner till I get a new compressor.

Edit - I should add that even when I changed the tune and added to the VE table so that STFT was around closer to 0 instead of the +10 to +15, it was still pulling timing. I believe if it was a clogged injector issue then I would see one bank have a long pulse width? Same if maybe it was a bad O2 sensor? The spark table compared to stock is not too different, actually a few degrees less in the places I'm getting lots of retard. I'm actually several degrees advanced on my C5 with similar cam. Bad knock sensor maybe?

Also noticed they disabled SES for forward O2s and lean/rich fuel trims. I assume because it would be tripped from their lack of SD tuning... So annoying paying a shop $500 to see they half-assed everything.