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Holy frijoles Batman, that helps a ton! It’s definitely at low airflow conditions. I’m buying a cable to try and tune on my own, so I’ll be saving this! Thanks!
Unless the PCM goes into some sort of "limp" mode if it doesn't detect the EGR hooked up and really starts jacking with the timing... again, I'm not an expert on 94-95 PCM's to that extent.
Absent that, in the normal code, here's what it does on timing vs EGR. Just 1 deg here and there. I doubt you'd ever feel 1 deg by seat of the pants.
Holy frijoles Batman, that helps a ton! It’s definitely at low airflow conditions. I’m buying a cable to try and tune on my own, so I’ll be saving this! Thanks!
I don't know... I wouldn't get your hopes up on that too much. I could be wrong, but...
20 mV on the O2 threshold and playing with the integrator delay may good be for optimizing things, but IMO what you're describing in terms of running issues goes way beyond what's being described in that document.
Unless the PCM goes into some sort of "limp" mode if it doesn't detect the EGR hooked up and really starts jacking with the timing... again, I'm not an expert on 94-95 PCM's to that extent.
Absent that, in the normal code, here's what it does on timing vs EGR. Just 1 deg here and there. I doubt you'd ever feel 1 deg by seat of the pants.
Agreed after reading this, this may not be the issue then. I’ll still program it out though.
I don't know... I wouldn't get your hopes up on that too much. I could be wrong, but...
20 mV on the O2 threshold and playing with the integrator delay may good be for optimizing things, but IMO what you're describing in terms of running issues goes way beyond what's being described in that document.
Besides it’s weird stumble if I’m half throttle or so, it runs fine. I’m thinking I’ll pull some data from the PCM once I get my cable and get some real data on what’s going on.
At higher rpm it seems to be okay, but sometimes I can feel by the SOTP dyno that something is off.
Probably because at higher RPM, it takes much less throttle to enter into Power Enrichment fueling. See table below.
You said you unplugged the AIR system. On the older 90-92 systems, the ECM would adjust the O2 sensor rich/lean thresholds by about 100 mV based on the extra O2 injected into the exhaust stream by the AIR system.
I'm not seeing anything like that in the 94-95 code. But, without that extra O2 in the exhaust from the AIR, the ECM may think you're running too rich and pulling fuel out. Combined with the extra scavenging effect that headers naturally have, you could be running a bit lean... again, this would show up only in closed loop operation (non-power enrichment) where the PCM actually reacts to the O2 sensor.
Probably because at higher RPM, it takes much less throttle to enter into Power Enrichment fueling. See table below.
You said you unplugged the AIR system. On the older 90-92 systems, the ECM would adjust the O2 sensor rich/lean thresholds by about 100 mV based on the extra O2 injected into the exhaust stream by the AIR system.
I'm not seeing anything like that in the 94-95 code. But, without that extra O2 in the exhaust from the AIR, the ECM may think you're running too rich and pulling fuel out. Combined with the extra scavenging effect that headers naturally have, you could be running a bit lean... again, this would show up only in closed loop operation (non-power enrichment) where the PCM actually reacts to the O2 sensor.
this is only in closed loop it happens. In open loop I have about 5-10 minutes of decent city driving before it reaches operating help and starts to act weird
Besides it’s weird stumble if I’m half throttle or so, it runs fine. I’m thinking I’ll pull some data from the PCM once I get my cable and get some real data on what’s going on.
Yeah, see my post above. If it ends up being the AIR system missing (and the headers have no provisions to hook it back up), then you'll definitely need to re-tune the closed loop fueling tables.
I'm not seeing any accelerator enrichment fueling tables in the 94-95 code like there is in 90-91 and 92-93. Maybe GM rolled those into main fueling tables. So that could also explain your stumbling during throttle transitions as well whereas you seem to be ok during steady-state driving.
Good move on getting the equipment to datalog. That'll probably tell you what's going on.
Yeah, see my post above. If it ends up being the AIR system missing (and the headers have no provisions to hook it back up), then you'll definitely need to re-tune the closed loop fueling tables.
I'm not seeing any accelerator enrichment fueling tables in the 94-95 code like there is in 90-91 and 92-93. Maybe GM rolled those into main fueling tables. So that could also explain your stumbling during throttle transitions as well whereas you seem to be ok during steady-state driving.
Good move on getting the equipment to datalog. That'll probably tell you what's going on.
Well, I pulled the air pump and tubing out yesterday, haha! So perhaps I’ll truly disable it in the tune instead of just unplugging it.
Thanks for all the tips here! I truly enjoy troubleshooting stuff if I get the proper “tools” to understand the situation. You’ve provided me with a bunch of great info to get started.
Yeah, I think you can simply take the parameter "Min Coolant Temp to Enable AIR" and set it to the maximum 150°C (~300°F). If the PCM doesn't enable the AIR, then it shouldn't be expecting to see the extra O2, so it should negate those effects.
Yeah, I think you can simply take the parameter "Min Coolant Temp to Enable AIR" and set it to the maximum 150°C (~300°F). If the PCM doesn't enable the AIR, then it shouldn't be expecting to see the extra O2, so it should negate those effects.
Which software are you using? I’m looking to get one of the free ones. Tunercat is $200 for the pro bundle! I just want to disable stuff (CAGS, ASR, EGR/AIR) and maybe tune AFR and O2 parameters if needed.
Which software are you using? I’m looking to get one of the free ones. Tunercat is $200 for the pro bundle! I just want to disable stuff (CAGS, ASR, EGR/AIR) and maybe tune AFR and O2 parameters if needed.
Pretty sure the '95s use the $EE PCM mask (someone correct me if I'm wrong). EEHack and TunerPro would be the way to go for tuning.
Cable came today in the mail. I’m going to download TunerPro and give it a shot. Anyone have any beginner tips? Or a link to a thread that gives the rundown on tuning? I planned on using LT1PCMTuning’s site since he has a tips page, but it’s still quite confusing at times for a newbie.
Okay, I did a datalog with $EEHack. I went with FlashHack since I am using an old laptop, and if I disconnect during flash at any time, they offered a program that can restore everything and avoid bricking my PCM most of the time...
Besides that, here is the data I logged:
I don't know much about what the data is telling me, but I assume the red on my AFR is no good. While driving, during the stumbling events, I would see that my Right Bank BLM would dip into the red. This also occurred with engine breaking.
I have also noticed that my right bank BLM is all over the place. When the throttle is at 0% it sits steady at 160, which I thought the goal was to have this at 128 +/- 15. Then as I drive it pretty much sits at 160, with some dips down to 108.
The left bank seems to keep itself around 128 fairly well.
If the BLM is sitting at 160, I think that means a lean condition, right?
