if you have 3 wire i don't 4 wire is really necessary. you have a tune problem not mechanical
if you have 3 wire i don't 4 wire is really necessary. you have a tune problem not mechanical
The O2 low grounding from the stock place at the thermostat housing then to the threads of the O2 low sensor COULD cause funky readings, weather or not that IS the problem, a 4 wire sensor wired direct, would eliminate that, and ensure a good signal.Originally Posted by tayto
That said, I am highly suspect of it being Decel ENLEANMENT.
No need to re-invent the wheel. But we can make it better
Ok cool I didn't order anything yet so I won't worry about it. I was looking into the proportional gains and I'm trying to make sure I'm looking at the right tables, are they "proportional flow gain factor vs MAP vs RPM" and "proportional counts vs slow o2 error" ? If so what am I looking to do with those? Get more cross counts when the issues occur? How do I know whether to raise or lower the numbers? Sorry for all the questions I haven't messed around with any of this stuff before.
The thermostat ground IS NOT for the O2 sensor or the ECM. It is for the AC clutch! Grounds for ECM are on the back of the passenger side head. I have put headers on a few TBI vehicles and only used a 3 wire because it would drop out of closed loop at idle. Have also used a 3 wire on stock when cat removed or high flow cat used. The stock 1 wire o2 on a TBI GMT400 truck is after the Y pipe merge right before the cat. No issues with ground there FWIW. He is also running shorty headers......
Maybe so, but my 94 stock had all sensor grounds at the t stat, including the one to the 02 low
All I was saying is that a direct wire from pcm to O2 makes sure of a good signal. Agreed that both 3 and 4 wire HEATED O2 is better than 1 wire non heated.
No need to re-invent the wheel. But we can make it better
I suppose. they only went to 4 wire O2s on the newer OBD2 era PCMs. I have a feeling it was to do with noise more than a good ground signal, but I am not an electrical engineer. I also suspect the older TBI stuff was less susceptible to that sort of stuff. I have seen lots of that era GM with multiport with shielded pairs and whatnot, stuff you don't see on the older stuff.
I have torn apart many GM TBI harness and the ground was always on the back of the head. What colour wire was on the thermostat stud?
I don't remember now. I tapped in at the pcm for mine and ran a new signal high and low from sensor to pcm.
I think you may be right about noise. It's not really a ground per day, but the low signal. What was explained to me is that the pcm reads the difference between the high and the low.
And to be clear, I'm not sure you don't have a tuning issue, but my understanding has been that you always rule out mechanical issues first before trying to FIX the tune. A 4 wire tied directly to the pcm, Might not fix your issue, but it would rule out interference, or the mechanical aspect. Then once ruled out you can move on confidenty.
That's just my 2 cents.
No need to re-invent the wheel. But we can make it better
I did a bit of research, looks like the P4 TBI stuff did indeed have the grounds on thermostat housing. most of the stuff i did was the C3 ECM , f-bodies, b-bodies and early C/K TBI stuff.
I know some of the buy back stuff the grounds got moved to the head.
No need to re-invent the wheel. But we can make it better
Still battling this even with decel enleanment and DFCO completely disabled though I've sort of just been living with it by dumping a bunch of extra fuel in that area so it only has time to climb from say 11:1 to 14:1 before I'm back in the throttle so i at least don't get a bad surge from climbing to 17:1. Tried adjusting some of the proportional gains but I have no idea what I'm doing so it didn't seem to help much though I did try small adjustments and large adjustments just to see if I was being a nancy about it, didn't seem to have much of an effect either way.
Had another issue this morning which was the first cold morning I've had the truck out in a while. I've been having an issue with running lean when the ambient temperature is low so I went through the trouble of installing a MAT/IAT sensor, cut the flag on in my bin, and set the MAT/CTS blend to .500 but it didn't appear to help at all this morning. I'm wondering if the flags for MAT sensor high/low, code 23/25, have to be enabled for the ECU to use it in it's fuel calculations? I thought I had read of people just enabling the flag itself for MAT and not the high/low flags but I'm going to cut those on just in case. Yesterday when I drove the truck home all the trims looked great and didn't notice any lean areas. Should I drop this number lower to add more fuel when cold? It almost seems like the MAT input isn't working but I know the ECM sees it because I can get the data on my adx file and it's reading correctly. I don't see any other tables I can adjust to adjust fueling across the board at different ambient temps, just AE adjustments for different temps. Otherwise I would have just adjusted that table than go through the trouble of installing the MAT sensor.
Last edited by 95GMC; 04-28-2022 at 02:39 PM.
Have you filed in your idle ve?with trimalyzer you can filter for idle flag and get it dialed in pretty easy only using data from when it's running off of the idle ve table. If you put an AFR error in your ADX, you can use that in trimalyzer and tune open loop. Since you have wideband, I would log a full open loop run and see how far off it is. The O2 only has a limited amount of time to figure out how far off it is.
No need to re-invent the wheel. But we can make it better
Just the sections where I'm actually at idle, pretty much just the 30-40 kpa range at 600-800 rpm. I haven't used trimalyzer, is it something in tunerpro or something I need to download? How do I go about putting an AFR error into my adx? I'll definitely do that, sounds like a better approach than what I've got going on right now
prop gains are only for closed loop, you are still running open loop correct? it sounds like you need to increase your VE table in those areas. has ASYNC been disbaled? I had a car that would do this weird jerking on decel, it was because async was coming on. Also just to make sure you have no EGR valve? charcoal purge line has been blocked (can hook up in final stages of tuning).
cold start still very much has to do with your VE table. get your IAT working if you wish but focus on tuning the VE table first before you start fussing with stuff like cold start. it is easy to get overwhelmed tuning.
Last edited by tayto; 04-28-2022 at 07:38 PM.
Well I had done my initial VE adjustments in open loop and thought I was pretty close minus the decel issue so I switched closed loop on to see if it would fix the decel issue but didn't make a difference. Also when I went back to closed loop my tune was lean across the board, now I've been fighting all that so I probably need to start over yet again. I just checked and ASYNC is enabled right now. That's right on the EGR valve it's gone and disabled. I haven't actually disconnected the charcoal purge but I will do that.
I think I explained the cold issue poorly, it is only ambient air temps changing that makes it run lean and not really a cold start. It can be say 30 degrees outside and the tune will be running lean across the board even after the engine is up to temp but then if I leave the tune the same and drive it in 60 degree weather it will run perfect and not lean at all. If I add fuel across the board to fix the lean issue at the colder ambient temp, when I drive again in a higher ambient temp it will be running super rich. I thought maybe the IAT would help with that but it hasn't seemed to make a difference so far. I definitely agree with easy to get overwhelmed tuning, I'm definitely there lol
Last edited by 95GMC; 04-28-2022 at 08:03 PM.
Trimalyzer is a program for analyzing data logs a member on here, Steveo, wrote. It is pretty cool because you can use it to combine more than one data log and makes tuning ve a copy paste affair.
I wrote a how to write up on using it with AFR error, and included an ADX with AFR error in it. Since you said your wide band uses a different scale, Maybe you can either change the scale in my ADX, or look at it and see how I did it. Not with computer now.
Write up is here
http://www.gearhead-efi.com/Fuel-Inj...-with-WIDEBAND
Basically you export your log file as a csv and filter stuff out. I think you may even be able to filter out canister purge. Not sure.
But would definitely look at using it, it's an Awesome program
No need to re-invent the wheel. But we can make it better
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