stalling out when returning to idle in park or gear
Hi all, i am having a issue with my ls swapped 1984 z28 stalling when coming back to idle in park and in gear. It is a 4.8l with a sloppy stage 2 cam, pac 1218 springs with a speedmaster ls6 style intake with a stock dbc throttle body, a th350 with no vss hooked up and a 0411 pcm. the car ldles great at 950 and doesnt stall when shifting in to drive but when i give it any throttle it overshoots the target idle and goes real rich according to my afr gauge and stalls out, i can catch it by feathering the throttle but it never wants to recover on its own. this is my first ls swap and also my first crack at tuning. I'm using some rochester 24lb fuel injectors from a 1997 lt1, which should flow at 28lb at 58 psi which is where my pressure is set. im running a walbro 450 with a aem return style regulator. The pcm i have had a pretty hacked sd base tune to begin with so i loaded most of a 2002 ls1 camaro tune and made slight changes. unfortunately i haven't been able to do any ve tuning yet as the cars not registered. Also i dont have the capability to log the wide band as its a older pro sport. I can up grade the control box but i'm not sure if my mpvi2+ supports wide band logging, if anyone has info on that I would appreciate it. i have driven the car about 2 miles and it seemed to go pretty good i just had to do alot of pedaling. I have tried messing with the throttle follower and cracker to no avail so i reverted them back to stock. I have checked and re checked for vacume but i can't find anything. I will post my most recent idle log and a log of the stalling as well as my tune. Thanks in advance!!
Last edited by z28dyson; 10-21-2022 at 10:14 PM.
Reason: Error on vehicle info
Look at your LTFT in the log.. It shows that the PCM is adding extra fuel due to a lean condition on both banks. When I look at a 3D view of your VE Table... I've never seen one like that before.. Ever.. Not saying it won't work... In the idle fueling areas on that VE table, your #'s are significantly lower than I think they should be... But that SS2 cam has a bit of over-lap at idle and that overlap allows unburned air into the exhaust and that may be why the log is showing so lean at idle.. Maybe it's enough fuel, but the O2's are just not happy about the amount of unburned air that they are seeing. Otherwise, I would try increasing fueling in the idle areas on the VE table and see how the engine responds to those changes. Keep a copy of your current tune so that you can revert back to it should it get worse, instead of better. As a test, go into your VE table, highlight the 400, 800, 1200, and 1600 columns.. then in the box type in 1.20 and hit the "X" to essentially add 20% across those columns.. Then burn it, then do another idle log and let's see what that does to the idle.
Without a VSS signal, I wonder how the PCM knows to go into the idle routines? Typically when you come to a stop and the PCM sees that the vehicle speed is zero, it then goes into the idle routine to control engine idle.. Since you have no VSS... I wonder how the PCM is controlling idle? Hopefully someone else will post up how the PCM knows it's idling.. It looks like it is going into the idle routines as the idle adapt STIT is working when your foot is off the gas.. Also, please note that your BRAF-or base running airflow is not correct and that may be part of the problem. At idle, the STIT should be ZERO.. or close to it within reason. When it's zero, or there-abouts, it means that your BRAF is close. Right now it shows that your BRAF #'s are higher than what the engine actually needs. Someone has already hit the idle underspeed and overspeed spark tables and calmed them down dramatically. For right now, until you get the idle dialed in, you may want to go back into the UNDERSPEED table and add some spark (10+ degrees) so that the PCM can add that spark to catch the engine from stalling. Some guys say to make the 0 and 400 column up to .28 in the idle spark tables to something high like 40 degrees so that as the engine falls into those areas due to other issues the PCM will add the spark and hopefully save the engine from stalling.. But I'd try adjusting the UNDERSPEED table first by adding at least 10 degrees to see if that is enough to allow the PCM to keep it from stalling.
I see that its a speed density tune.. Have you looked at the MAF table? Again.. I've never seen one ZEROED out like that.. but I'm not a pro tuner either so maybe there is a reason they zeroed out the entire table. Your PE is set to 12.04AFR across the board.. Interesting. Usually this a progressive trend towards RICHER afr as the RPM's increase, or more specifically richer where the engine makes max torque.
In conclusion I think your return to idle problems are related to fueling in the idle areas, and BRAF. You DO have throttle cracker air that is adding to the equation.. but for now... work on the fueling and Base Running Air Flow table. I'm hopeful some of the smarter guys will post here and help you out as well. If you are not sure how to address the BRAF tables, there is a RUSS K idle config process that you can go through that will help you. BUT you need to fix the fueling FIRST otherwise you will just have to keep repeating the Russ K idle config as you dial in the fueling in the VE TABLE.
Thanks for the response. I will try some of those changes this afternoon. I never noticed how flat that ve table was as I never looked at the 3d graph, I think I'll paste in the ve from the my original download and add some fuel down in the idle area, it looks much more normal. I also noticed the airflow thing watching the log yesterday as well, it seemed to only want like 8gps and was calling for 24. I did bump the timing in the high low octane to 35 or 40 in the 0-800 range and in the base p/n and drive timing tables and it would still stall. It hung in for a few seconds longer but still ended up eventually stalling out. It really makes it a pain to drive, there is a few miles of stop and go when I leave my house so I was hoping to get it little better. I know I really need to dial in the ve before I play with the idle but it would be nice if it didn't stall every time I let off the throttle.
Here is the tune with the original ve that was in it I added 20% to the idle area. I also added 15 degrees to the underspeed spark, starting at 10 then i increased it to 15 I aslo made the low rpm idle areas 40 degrees and I removed some braf. it still stalls like it did before but did seem a little better as it wouldn't stall every time. Now it stalls going from park to gear 50% of the time. On a good note the stit seemed to eventually level out to almost 0 so that's a slight improvement anyways. Thanks again for your suggestions
Okay.. TOO MUCH advance in the idle spark regions.. You only need 40 degrees in the O, and 400, columns.. Not the 800 column or anything higher. The idea is that if that idle rpm dips too low, then suddenly that extra spark is there and available.. You DO NOT WANT it idling in the 30-40 degree range! Your idle is almost completely confined to the 800+ columns.. Take some of that spark OUT.
Also, it's easier to see what is actually happening with LTFT + STFT average error graph and it will show you the average between them and you can adjust from there. Or, turn off LTFT and just use STFT and the STFT error graph and go from there. Cell hits in your graph need to be at least 25. In looking at your current VE Table in 3D view... it's still odd... Why not start with just a stock ve table, and make changes from there? I'm including a tune here just for you to COPY the VE Table into your tune, burn it in, and then do another idle log. Either write a filter so that there is NO DATA collected until at least 131 degrees, OR, don't start logging until the engine coolant temp is 131+ degrees. Incorrect fueling BELOW the temp where it goes into CLOSED LOOP is handled in the OLFA table.. Above the CLOSED LOOP coolant temp (131 in your tune) is where you need to be logging. I'm including a tune here that you can copy the VE TABLE from. Also this SAMPLE tune has the IDLE SPARK in DRIVE and P/N corrected to what yours should look like until you get the idle issues resolved. Once you get the IDLE stabilized, you will want to go back and REMOVE the 40 degrees from the 0 and 400 columns as it is just a crutch to help you temporarily until you can get the idle sorted. It is NOT to be left that way.
Once you burn the VE table from this sample tune over, and get the vehicle up to operating temp, and begin scanning.. Go into the vehicle controls and go to the spark tab and LOCK the spark in at about 22 degrees. That will stop the timing/spark advance from bouncing around and will better help you drill down on correcting the fueling... Also, instead of blipping the throttle, you will want to raise the throttle up to 1000 and hold it as steady as possible there for at least 10 seconds, then at 1200 for 10 seconds, then 1400 for 10 seconds.. do this up to about 2000 rpm.. Remember you want NO quick blips of the throttle! You want nice, SUPER SLOW transitions in RPM increase.. DO NOT BLIP the throttle for any reason as you will skew your data in the log.. You will see that the different cells will be hit in the table as you SLOWLY increase the engine RPM and with your cell hits set at 25 in the graphs you will be getting good data. After you get that log done, post it back here and we will continue to drill down on the fueling, and then we can move on to Base Running Airflow.
I included here the LTFT + STFT average AFR error graph so that you can see how it is set up. You can leave your LTFT active with that graph and it will average them out for you automatically.
so I loaded the ve and made the spark corrections. I'm still learning to navigate the scanner, I partially figured out the graph configurations but couldn't get it to hit any cells when i made the stft+ltft graph. So instead I went in to the tune and disabled the ltft for now. i logged the stft but only 9 cells hit. When I tried to lock the timing at 22 it stalled out but I was able to lock it in the log. I've attached while slowly running it up in the rpm's. It did seem to run much cleaner when it was idling and my afr gauge was fluctuating between 14.8 and 13.8. ill also attach the tune with the changes. I do admit I'm not all that computer savy so not only am i learning how to tune I'm learning how to navigate computer software hahahaha.
Okay, just now getting a chance to look at this... So as you can see from your log-the timing all over the place.. You are still hitting 40+ degrees at idle-I understand it's the PCM trying to catch a stalling engine, and that it's just a byproduct of a bigger issue. Your fueling seems to be close on the error graph in the idle areas.. However, there is a HUGE disparity between Bank 1 and Bank 2. Look at the 3:43 time on your log... You are at +25 on Bank 1, and -18 on bank 2... Usually a disparity that great between banks is pointing towards another issue... Is it possible that you have the wiring for the front O2 sensors criss-crossed? Meaning could it be that the wiring harness connector for B1 O2 sensor is actually connected to Bank 2, and B2 on B1 O2 sensor? Read through this post: https://ls1tech.com/forums/pcm-diagn...chart-jpg.html
As that post indicates, you can just unplug, ONE, or the other O2 sensor and do another short log and watch to see that the O2 sensor that you unplugged is now the one MISSING from the log.. If you don't have the O2 sensor wiring criss-crossed, then there is something else wrong mechanically. Check the O2 sensor wiring FIRST before we move on... That variance, or disparity, between those banks is telling us something...
Thanks for getting back to me. I had a chance to check every thing over and all was good on the wiring side for the o2 sensors. i did notice those were out of wack so i went back and watched all my previous logs and the readings were all consistent with each other. I went through and kind of started fresh on the tune using mostly camaro SS tables aside from the ve you sent over which seems to work great for now. It looks like I got the timing craziness under control and i could probably pull a little out. I also fixed my stalling issue for now by raising the proportional and integral rpm enable tables under the idle\rpm section to 2000, I don't know if that is the right way to do it but it seemed to help. With no vss it wasn't going in to adaptive idle at all after i applied any throttle. I will attach my current tune and a fresh log from today. The weird thing is i didn't touch a thing and the stft seem to be in check now so I'm pretty baffeled as to what happened there. I'm using a cheap amazon harness given to me by a friend and it has been nothing but problems since day 1. So I Wouldn't be surprised If I end up having more issues. My heater core also decided to take a dump and spray coolant all over my car the other day. I'm also suspect that my oil pump or the pickup tube Oring are having problems because i started having odd oil pressure issues during my last few logs. So I guess I have got some work to do before I can drive this thing anyways. Thanks again for taking the time to look at these logs and tunes for me, I'm a total noob at this stuff i'm a old school carb guy but it was time to make the leap as I do plan on going turbo eventually after I get a handle on the tuning.
I just noticed something, In that log where the stft was going crazy I had disabled the ltft in that tune. This time I left them enabled and they were in check. That may have had something to do with it I'm guessing but I don't know.
That looks SOOOO much better! Notice that Cylinder #7 is misfiring a bit more than the others.. you may want to look into that.. check the plug.. maybe replace the wire... and move that coil to another cylinder and then watch the next log to see if the misfire follows where you moved that coil to. I see the disparity between bank 1 and bank 2 has almost completely disappeared. It seems the only thing needed right now is a reduction in the IAC counts.. notice that you are now PULLING timing to get it under control. You have increased your base idle RPM to 850, and yet you are idling a little bit higher... Your timing-the white line in your log is almost perfectly flat-AWESOME! But... Your IAC counts are still too high.. at operating temperatures you want them in the 30-50 range... try CLOSING the throttle set screw just a little bit.. like 1/8 turn at a time until you can get those counts down.. Whatever changes you made really worked.. that is a very good looking log and you are close to perfection. I've attached a VE table with updates for the idle areas based on your log. Try this VE table for another idle session-ONLY recording at temps above 131, and let's see where this puts you.. Really impressed with this current log. You have made major strides with this current update.
I found the misfire, #7 plug wire was barley hanging on so I swapped #7 with #1 plug and wire and misfires are gone. Thanks for catching that. I also got the high idle under check by lowering the proportional and intergral tables and creeping up on them until the stall went away and the idle was at target. That also lowered my iac counts to 50-60 which was great.
Up above in post #10, you said "I also fixed my stalling issue for now by raising the proportional and integral rpm enable tables under the idle\rpm section to 2000". As I review your current tune, it looks like you have "IDLE PROPORTIONAL ENABLE RPM=700" and "IDLE INTEGRAL ENABLE RPM=90". I believe, and someone can correct me if I'm wrong, that those ENABLE tables essentially mean you have NO IDLE PROPORTIONAL CORRECTION until the commanded idle speed/rpm, is greater than, or less than, the actual idle speed by the RPM you assign to that field. In short, by changing the IDLE PROPORTIONAL enable RPM to 700, then the computer will not attempt to correct an idle issue (LTIT? STIT?) until your ACTUAL idle is MORE THAN 700 RPM above/below your commanded idle speed. In essence, you have *almost* set up it up to run as an OPEN LOOP IDLE scenario until the RPM variance is above or below the commanded idle speed by 700RPM. In your case, a commanded idle speed/rpm of 850 means that the engine would have to be idling at 1550 BEFORE the computer tries to take control of the idle. Or, the same could be said if the RPM was 700 RPM low-which would be 150rpm and at that point it would not matter because the engine would be stalled.. I hope I'm expressing what I believe to be the case here.
There are OTHER ways to change it over to an OPEN LOOP IDLE TUNE if you wanted to go that route. Have you seen this post; https://forum.hptuners.com/showthrea...op-idle-tuning
It discusses the methods utilized that some tuners resort to when an open loop idle is desired, essentially removing the PCM corrections at idle. I know that people like Russ K have the KNOWLEDGE and ability to tune well enough and still leave idle correction active... For others, like myself, who find PCM idle correction with a big cam more of an ongoing fight than a partnership, going OPEN LOOP IDLE might be the easier way.. but not necessarily the best way? I'm sure there are some compromises when removing the PCM from control of the idle routines. Maybe some of the wiser guys will post up what the trade offs are when going to OPEN LOOP idle.
From your most recent log in post #13.. Your spark is again all over the place.. That might be because the PCM can no longer attempt to control the idle through Proportional. As of now it can only try and regulate idle through spark? Please note your IDLE STIT is showing -2.8 meaning the BRAF is still not correct. I did not see above you making mention of having done the RUSS K idle config yet. Have you done that? If not, I would be doing that now to see if you can get the BRAF dialed in, and that might be all that is needed to calm the spark down. See-saw patterns as it relates to the timing-from what I've been told-are a sign of something else being off in the tune and usually more work is needed to correct that.. When everything is right the spark advance will move very little up or down while at idle.
I've been reading on the IDLE PROPORTIONAL and am just not quite able to fully understand it yet. From what I've read it is simply a routine that the PCM utilizes to push the AFR above the commanded 14.68, and then times how long it takes the O2 sensor to report LEAN, then it drops the AFR BELOW 14.68 and then times how long it takes the O2 sensor to report RICH, and then uses that data to update the STFT, and over time, the LTFT. In your case-setting the enable rpm to 700 RPM above commanded idle means that you have essentially disabled it at idle all together. I guess I have a LOT MORE reading to do before I reach a point of understanding. Nice that you took a guess at it and it worked. But I'm wondering what other things are now altered as a result of doing that. Everything seems to be tied together with HPTuners and changing one thing can change a LOT OF other things without you knowing it. With that said, I wonder if the BASE RUNNING air flow table even matters since you have proportional disabled.. If it's idling, and not stalling, maybe you have reached the "leave it alone-it's fine!" point..
i have been reading till my eye's hurt about the proportional and integral tables and I'm not sure how raising them made it not stall hahaha I had it a 2000 on the log on post #10 but it wouldn't hit target idle, so i went back and returned it to stock and raised it in increments until it wouldn't stall and was staying at target idle and it seemed to work. I might attempt to try the ol idle and see how that goes. I have not yet done the russk idle yet I still haven't found a solid link for the correct info, most of what I'm finding is second hand stuff but I'll keep searching. I am also having a rough time making my histograms work, i can set uo the table but then it doesn't record anything. i might just drop the values for the braf tables to 8, that's what it seems to like. I need to jump my heater core before I can log again, last time i logged it the heater core completely exploded and made quite the mess.
I’m on my phone so can’t look at the tune or logs. But your initial post, you said you have a dbw throttle body but you have a Camaro operating system.
The 98-02 f cars came with a drive by cable throttle body and the ls1 corvettes came with the dbw and of course the later gen 3 trucks. This could potentially be contributing to your issue here.
Did you mean you have a cable throttle body or do you actually have an electronic throttle?
Last edited by Firebirdmuscle; 10-20-2022 at 11:49 PM.
Sorry for the confusion it is drive by cable. It has a stock truck throttle body. I have a cheapo 92 but it wouldn't run worth a sh*t with it so I bought a good used stock tb. I just got another idle log I will post up later this afternoon and i took it for a short ride but didn't log it, it's tourist season up here so I'm dodging out of state people not paying attention to the road because of leaves.
I found some of the russk idle files today but couldn't get them to open for some reason Ill keep working on that. What I did do was reduce the braf closer to what it wants in my log which was around 5.5 g/s and I cut the under/over speed timing by about 30%, that seemed to calm the timing jumping around so much. I took it for another 3 mile ride and tried to get a log but my lap top wouldn't connect to my mpvi while I was driving, It may be time for a new laptop. It did run pretty good but on the rich side my wideband was between 13.3-14.5 the whole time I was cruising at about 2-2500 at about 40 and 50 mph. It was still trying to stall while slowing down but it was at least 50% better than it was last time I drove it, I could catch it easily and keep it running and sometimes it was fine. when I got home I shut it down for a hour or so, then went to pull it in the shop and it would start fine but wouldn't hold a idle at all. I messed around with it a bit and it wouldn't hold a steady idle at anything below 7 g/s of braf so that's where I left it for now. Aside from the stalling it drove really well and seems to make good power, i didn't beat it too hard but I rolled in to it slowly a few times. Definitely a lot better than the stock 350 I pulled out of it. Attached are my current tune with the changes I made and the log I took when I first fired it up today and another while I was messing with the braf to keep it idling again. Thanks again for taking the time to look at these files.
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