Troubleshoot surging at idle

[only_1]

Can anyone look at my data log and tell me what I have set up wrong to make my truck surge at idle?
I attached logs of just idle when surging. I also attached a longer data log of driving because it does it when fully warm and holding rpm. Seems like I have a dead-band issue making the system hunt for O2. Cold idle when in open loop is pretty good. Hot idle after a driving has a clear hunting issue with AFR bouncing between 12 and 17.
I haven't been able to get my autoprom to accept the 0-5v from my AEM gage, so that data is not there. - I am open to suggestions on getting that working too. I may just wire it to the B16 pin in the aldl as people suggest.

Thanks for all the help so far. The truck is running much better now than it was after my "professional" tune.
-It does run good during light acceleration. Its the cruising that it stumbles.

[sturgillbd]

I have been band-aiding the same issue for a while. There are proportional gain settings for the O2 at idle which can calm the idle surge down. Lower the proportional gain settings under O2 PID Idle Parameters in Parameter category view. I also lowered the number of counts in Proportional Counts vs. Slow O2 error to smooth the surging at cruise. This table is under Fuel Trim Parameters. There is also a table in there called Proportional Flow Gain Factor vs MAP vs RPM which has some effect on the O2 switching. I finally repaired my ostrich emu and hopefully the weather will break soon and I can do some more testing. I haven't been able to find a normal proportional gain setting in $0D for the O2 sensor. When you make changes, look at the O2 swings using Show Data Monitors to see the results of your changes. The surges are caused by the O2 gains and overshoot. You can see the surge in monitors while viewing live data. I usually turn on O2, BLM, INT and Calculated airflow since I added it to my adx file and modified my bin to show it. Some of the others may be able to chime in and have a better method. I have been trying to figure it out on my own. I run a Howards cam 180245-10 so my calibration is quite different from stock. I'll look at your datalog this evening.

Hope this helps,
Brian

[only_1]

That cam is a bit more aggressive than mine. I have comp 08-304-8. I don't know if it's the low injector pulse width? I also see that it's desired afr is in the 13's?
I am ok with the 13's but didn't know if that makes it approach the edge of o2 tolerance quicker?

[sturgillbd]

I just reviewed your idle log file and the idle timing is fluctuating a lot. The PCM uses timing to make fast idle changes instead of trying step the slower IAC valve. Can you post your bin? First thing I would do is adjust the throttle stop screw (minimum air) for about 10 IAC counts with the engine fully warmed up. I would also adjust the VE table to get the BLM closer to 128. You are sitting at 105 which is rich and the PCM is pulling fuel to compensate. If you still have surge, you may have to make changes to the idle overspeed / underspeed spark tables. I zero'd out the idle over/under speed tables to calm my idle surges down a long time ago. I could probably go back and repopulate the tables with some values but overall my idle is decent considering my cam won't have a smooth idle. Attached is a screenshot of the spark tables.

[only_1]

I edited the original post to include the bin file. I have been updating the VE tables per the BLMs with the spreadsheet someone had put together (sorry, I forget who did). I moved the low rpm idle VE values down to offset that 10X numbers.
Take a look at the Bin file and let me know if I am just wrong anywhere. Suggestions and criticism are welcome!

Thanks for all the help!

[stew86MCSS396]

That cam is a bit more aggressive than mine. I have comp 08-304-8. I don't know if it's the low injector pulse width? I also see that it's desired afr is in the 13's?
I am ok with the 13's but didn't know if that makes it approach the edge of o2 tolerance quicker?

Didn’t realize you were the op. lol IIRC in another post you’re using 80#s with 20ish psi??? I’d like the experts to chime in on this one as I’ve yet to experience this myself. I too noticed on your log the small pulse widths of 0.xx at idle.

What adx are you using? I couldn’t see the target AFR while viewing your logs.

[sturgillbd]

I have came in late in the game obviously. If you have 80lb injectors and running them at 20psi, you have approximately 100lb per injector and you may have a little too much injector. You can try to lowering the minimum BPW times under BPW Limits. I don't know how much it will help you. I am running 61lb/h injectors at 27psi currently and idle fueling seems ok. Can you lower your fuel pressure? If so, you may have an easier time tuning this thing. Another thing I noticed is not a lot of spark advance at cruise. How heavy is this vehicle? I'll look at your bin this evening when I come back in.

Brian

[only_1]

Didn’t realize you were the op. lol IIRC in another post you’re using 80#s with 20ish psi??? I’d like the experts to chime in on this one as I’ve yet to experience this myself. I too noticed on your log the small pulse widths of 0.xx at idle.
Yeah with my injectors, at 20 psi I should be around 101 lb/hr for my injectors.

What adx are you using? I couldn’t see the target AFR while viewing your logs.
I am using the 217_OD_v250 adx

[only_1]

I have came in late in the game obviously. If you have 80lb injectors and running them at 20psi, you have approximately 100lb per injector and you may have a little too much injector. You can try to lowering the minimum BPW times under BPW Limits. I don't know how much it will help you. I am running 61lb/h injectors at 27psi currently and idle fueling seems ok. Can you lower your fuel pressure? If so, you may have an easier time tuning this thing. Another thing I noticed is not a lot of spark advance at cruise. How heavy is this vehicle? I'll look at your bin this evening when I come back in.

Brian

Yes, I can adjust the fuel pressure to be lower if that would help.
The truck is a 1994 Blazer Fullsize. I think its around 4600 lbs.
The spark map was something I got from Fast in my other post. I have not changed it much since I got it from him.

[only_1]

I am going to start over with setting the throttle body blades to idle with IAC closed when hot. I wonder if that isn't the part of my problem. Either way, some times its best to start over at square 1.

[sturgillbd]

Twist throttle screw clockwise 1/4 turn. Look at IAC counts. Adjust only when hot. Keep turning clockwise until counts drop to around 10 or a little below in park. Shut off engine for approx 10 seconds (until PCM fully powers down) then restart. See what your counts level out at after a couple of minutes idling. Your counts weren't extreme but it needs a little more air past the blades. This helps the fueling at idle due to shearing action of air going past the blades. I am downloading your bin now and going to look at a few things
Brian

[sturgillbd]

Your datalogged spark doesn't match what is in the bin file. I have been trying to find what is causing the commanded spark advance to be lower than what is in the tables. Most places I checked it was off by approximately 5 degrees . I also notice your egr is commanded on the whole time the vehicle is running. I will dig further as I get time.

[only_1]

There is no egr on the truck. It is plugged off.

[only_1]

Would a vacuum leak cause these problems?
If the EGR is always on, in the program, it would mean that the EGR spark correction would always be on right? So that would be the 4 degree drop in timing?
-I zeroed this out for the next run to verify this, in addition made changes to try to disable EGR in general.

[sturgillbd]

Don't think you have a vacuum leak. Something is commanding the egr on and it seems like you have it disabled by scalars. I did a bin compare between your bin and BJYL and found several differences outside the defined parameters. You may need to start with a fresh copy using your timing tables etc .

When replaying your datalogs, do you see the EGR being on all the time?

Brian

[only_1]

I noticed the differences too. I didn't know what caused them. I assumed it was the guy who attempted my tune before. I will poke around the forum for a clean version to start with and input my changes.

[only_1]

As recommended I created a new bin file from one I found on here. I put in the tables for fuel, timing, egr, etc. I still have the idle hunting problem. The problem is muted when the truck is at idle in gear, but very evident in P/N. I attached the bin file I modified and the log file. Hot idle happens at the end of the file.

I am getting tired of fighting this thing. Do I just put in a Vac Ref Fuel Pressure Regulator and put the smaller injectors in?
To me that would add complexity, but I am not sure what else to do at this point.

I have looked but have not found an explanation of all the parameter use equations. Can anyone point me to these so that I can see how each is used to calculate what the computer is commanding?

Thanks!

[only_1]

Why does my fuel pump voltage change when sitting at idle?

Does ECM change voltage or does it just monitor it?

I will be very happy and yet frustrated if my problem is something like a weak fuel pump relay.

[sturgillbd]

I'll view your bin and datalog this evening. I got called out to work yesterday eve and didn't get home until about 7:00 am this morning. I will make some adjustments to your bin and you can try them to see if it calms the idle surge

[only_1]

I tried a few things with no real change. I think I am at the point of bumping idle speed up to 800 or running open loop idle. Either would be fine.

[sturgillbd]

Turn the throttle stop screw clockwise another 1/2 turn. Try this bin after pulling power to PCM for 10 seconds or so to clear all of the learned values. Warm the engine up and do a short datalog with about 45 seconds of idle at the end. Lets see if this calms the surge down some.

Brian

[only_1]

So the timing change seemed to help quite a bit. The timing now stays pretty solid. It had one little bit between log 1 and log 2 where it almost died, but then rev'd back up and settled down again.
The idle afr swings seem to be better. I wish I could get the autoprom to accept the wideband signal so I could show that as well.

[sturgillbd]

I'll review the logs later and get some ideas. I zero'd out the idle speed correction timing tables. There were also some adjustments to the iac counts vs % airflow table and of course the spark tables. Some of this will have to be done with trial and error until you get it how you like it. Do a bin compare between the bin you posted and the edited one. You can put things back to orginal one table at a time and see which change made the most difference. I noticed your IAC did move a lot and there are some proportional adjustments that can be made to calm that down also.

[only_1]

Thank you for the help. I will definitely use these corrections.

[sturgillbd]

The adjustments have definitely calmed your surge problem. Only thing I see that stands out is your IAC counts are still pretty high at idle. I would turn the minimum air screw clockwise until you have 0 counts at idle with engine warm. I would turn off engine for about 30 seconds then restart. Let the engine get back in closed loop and settle a couple of minutes then turn screw counterclockwise until you get 8-10 IAC counts . It may take a couple of adjustments to get close but you need more air across the butterflies and less through IAC. If your throttle body has never had the plug removed, you will have to remove the plug first. In this pic , it is called minimum idle screw. IAC counts should show while connected and engine idling with the data dash pulled up.

[only_1]

When I get down close to that few IAC counts, I get close to triggering tps off 0%.

[sturgillbd]

When you turn key off for 10 seconds or so, and turn key back on, the pcm resets the zero throttle position.

[only_1]

Now that we have made some progress on the idle and running, I have another question. It seems like when coming to a stop, or slowing down in general, the truck is holding on to the gear. Which parameter am I missing that would release it from engine breaking quicker?

[sturgillbd]

There are decel fuel cutoff parameters and also tcc lock/unlock parameters. Does it feel like the torque converter isn't unlocking or engine braking? I have a manual trans so I cant be of much help on Auto parameters. There are several on here who have done tuning on the trans parameters if that is what you are needing help with.

[woody80z28]

http://www.gearhead-efi.com/Fuel-Injection/showthread.php?829-AutoProm-ADC-Interface-Channels-Set-up-in-TunerPro!/page3

There's info there how I set up my AEM wideband. I also had trouble with the 0-5v for a bit.

Fighting my own surging idle on my v6 of similar cam duration too...

[only_1]

I have had a few things going on outside of working on my old GMT400. I got back to it a little last night. I found that my timing tab is off by 2 degrees. So when initial timing is set to 0 by the tab, the real timing is actually 2 degrees retarded. So my question is how do I deal with this in the tune?
I'd like to leave the external parts alone so that the next owner can set up timing as they should with a stock vehicle to 0 degrees initial on the tab.
The $0D mask doesn't seem to like negative values for initial timing. Do I just add 2 degrees advance to my timing table?
I basically have the timing table from fast355 yet only changing some in the idle area to keep it from surging (May not have been due to timing)

[ony]

move the dizzy 2 forward and remark plate

[only_1]

If I am remarking the plate, do I still set to 0 or am I better off to put in some additional mechanical advance?
Since the great majority of the timing table is advanced, it would seem that adding some mechanical advance would be beneficially to stability.

[ony]

most bins are set at zero advance on the dizzy

[ony]

some one on here recommended to zero out the stall saver, I haven't tried that yet I don't have a radical cam but it idles and drives better at low rpm's if the base timming is 0 bin set at 22-26 degrezz at the kpa and rpm it's ideling at