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Thread: 94 EE surges in SD closed loop at cuise and acceleration

  1. #1
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    94 EE surges in SD closed loop at cuise and acceleration

    I have been tuning for about 4 months now with great success though I have so much to learn. I switched to SD 2 weeks ago due to how good it runs with no split BLMs and power at WOT. I have been using VEMaster and has really improved cruise below 3k. It has been cruising smooth as silk until a few days ago. After this issue started I noticed the motor runs very smooth after I flash a tune until it reaches CL mode then it starts surging and slight stumble off idle. BTW these tunes are for speedo, PE and such nothing to do with cruise. Even after 40+ hits in each cell and I force OL it still does this same issue. It's only after a flash tune or I reset BLMs it runs so smooth then the second CL come into effect it surges and stumbles off idle. I can reset BLMs and lock it in OL and we are good then I remove the forced OL switching to CL it does this yet again.
    I must be missing something and at a loss of ideas to fix this issue. I will say that my BLMs are great in CL besides at idle cell 16 which are 108/108 but I believe this is a false reading without the use of wide band O2s but thats maybe another story. I just don't see how BLMs can be 126-130 on both with a surge. What you guys think, Thank you

    94 LT1, LT4 heads, LT4 hot cam, Lt4 intake, long headers, stock TB, new O2s, new fuel reg, new opti and new other crap

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    It sounds like it's going lean at idle. Do your O2's have a good source of power for the heaters? Did you modify the integer delay time for the extra length in the headers? O2 sensors will read a false rich for a bit as they cool down from operating temperature hence my question about the heaters. I've had the same problem before. Come down to a idle and the engine starts running like crap and I traced it back to the O2 sensor not working as it cooled down a bit.

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    Thank you Lionel, the delay is actually one thing I havent even thought of since the first times I started tuning. My settings now for O2 INT Delay are:
    800
    275
    200
    175
    162

    I never thought that INT Delay would cause an issue like I have but it does make sense. What do you recommend I set it as for a start, I'm guessing lower?

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    Set it higher. For example, if the 02 sensors are 3X the distance from the exhaust ports then try going 3X higher.

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    Thanks the O2s do have battery power and have actually checked with infrared temp gauge after 30 sec or so of key on only and are same temp. I was guessing INT delay lower because of the online bins that I have for comparing are lower. The other thing thats got me is it was running great with these delay setting until few days ago. I understand we my have rough running after a flash until the ecm gets enough hits in each cell and learn.
    I do believe I'm getting a false rich at idle and may actually be lean but header temp at idle are in spec and playing with Steveo's EE hack has kinda confirmed this. Header temp are a little off as far as individual temp and haven't messed with Ind Cyl Fuel Trim yet. I do remember messing with this parameter before and that did cause a surge. I set ind fuel trim all to 1.00 as of now and has been running fine but again that's another day. I'll give the INT Delay a test today, Thanks
    Last edited by troutdog311; 10-18-2015 at 06:34 PM.

  6. #6
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    Yes, I doubt the delays will fix it. But, something is off with the closed loop operation because what you're describing sounds like its tuning itself to the lean side. What are the logs showing?

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    Well we took the car out today. Without resetting BLMs I did a 2-3 min warm up. I usually let it get in CL before I drive out but we were in a little hurry. It was a cool morning and took much longer to get in CL due to temp. It drove so good I mean very smooth getting up to speed even had very responsive throttle and nice idle. I didn't get on it but there are a few stop signs here and was just amazing pulling off from a start. I'm sure you know what I mean by this but I have a very good ear. I could really tell every cyl was hitting just right at a 2200-2400 cruise and no abnormal flutter in the seat of your pants. I have an amazing fiance that has been so supportive and very knowledgeable of the basics of tunerpro. She is my copilot and very good at calling out BLMs, Cell, Loop and what not.
    Just as soon as I noticed the flutter/surge she calls out CL mode commenting what did parameter did you change lol I'm like nothing. Come to a stop sign and idle sounds odd like it's not as loud and oddly smooth that I know may sound weird but she even noticed this. Pulling off I had to feather the throttle to get the car moving and fully let off clutch. It was a 30 min drive to or destination. The surging did get better halfway there but not to my satisfaction. Idle and stumble from a stop also got much better but again not to my liking with a very rich exhaust smell. As we pulled up to a stop it was very rich smell BLMs at 108/110. I had to hear the ole lady complaining with " My clothes smell like exhaust" lol.
    Getting ready to go home I decided to use Scan9495 to reset BLMs and lock in OL, and it was just amazing in every way. Throttle, cruise, idle and starting off from a stop just great also. We did notice a slight rich smell at a stop but nothing like in CL.
    I don't want to deleted out CL "yet" in tuning because I feel like I'm just band-aiding the problem and will bug me till I die. Like I've stated this issue just started a few days ago with no change in tune. After flashing or BLM reset I have made sure to get at least 40 or so hits in each cell that it will go in anyway before making decisions on the tune currently used. O2's look great seesawing high/low like twins. I have noticed that the BLMs on right side is 5-7 higher than left at times though the ECM evens these out in a matter of seconds. I just wanted to tell you guys about today in hopes of giving more info that help me find what the heck in going on.
    Thanks for helping

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    Basically it can only be once it goes into closed loop the computer is pulling or adding too much fuel for what ever reason. The only thing that has changed is the outside temp is cooler and have read the SD mode can roar it's ugly head when the outside temp changes. It could be O2s but they are less than 4 months old and receiving batt volts. It could be exhaust leak but I have replaced the header and collector gaskets. I have listened with a hose to my ear for leaks and can't hear any. How sensitive are these cars to exhaust leaks. I hope a leak smaller than a needle don't effects it.
    I'll be playing around later and let you guys know what I come up with.

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    BLM <128 means the PCM is removing fuel. The fuel can't be rich with the BLM @ 110 if you started out with the fuel good and the BLM @ 128 while in open loop.

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    Well turns out I do have an exhaust leak on drivers side. I got the car on ramps can clearly hear and smell it. On both cyl 3 & 5 it's leaking around the header tube on bottom. These must be some cheap headers because I have never seen headers leak around the tube where it's welded terribly. I'm going to remove it this weekend for repair. I drove it all day yesterday with open look locked and was smooth as silk. I guess these cars are very sensitive to exhaust leaks, it really isn't bad tho it is a leak. Thanks for the help

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    I did get the exhaust repaired but check this out. Well I took the car for a long drive yesterday. It still has a surge though seems to be getting better. Talking about the stumble, it would stumble one min then be perfect another time. I did see something quite odd with my Timing vs RPM vs MAP vs TPS%. The times that it stumbled Very bad from a stop the MAP would max out 95+kPa just as the throttle is pressed and timing would drop below 10 degrees. At one point it kept stumbling over and over so bad that I almost didn't get it to move. Idling at 950 I would press throttle to 10-12% MAP would jump to 98kPa and timing dropped to 11 degrees, stumbling this made the RPM drop to 500 which then made the timing drop to 6 degrees. Then I was pumping the throttle like it's carb car trying to get to wake up. Just as MAP dropped, Timing raised to 32 and RPM slowly got to 1400 not to mention TPS was around 47% trying to get it to go, it hit 5k in a split second and drove fine the rest of the way home.
    I understand at X RPM and with X MAP = Timing. I know there are other spark parameters but I'm trying to keep this short and hopefully simple. This all makes sense when looking at the Main Spark Advance Table but what up with that MAP. I have looked at logs just before this stumble accrued and none of these have the MAP Maxing out just off throttle. What could cause this? This started this stumbling and surging after my 3rd VEMaster log. It weird because it was driving like a different motor for days then got up to drive it and all of these problems just came up. I also noticed that once or twice during my 30 min log yesterday MAP maxed out just sitting there idling with Zero throttle. I just replaced this MAP but could it be faulty. I'm guessing this could also cause surging. MAP does go _/+ 2kPa at cruise but nothing crazy like I mentioned. What ya'll think?

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    MAP kPa is 55 at 950 idle timing 30 degrees. In all the logs that had no stumble MAP never reached over 65kPa it's only when MAP hits 75+ and goes in the that corresponding spark cell. I also noticed last night I had a little spark retard that I have never never had before though I did almost run out of gas and got it at some old run down looking gas station. Just wanted to throw that in there, Thanks

  13. #13
    LT1 specialist steveo's Avatar
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    I also noticed that once or twice during my 30 min log yesterday MAP maxed out just sitting there idling with Zero throttle
    the only time MAP should be above 80+kpa is when you're flooring it, or the engine is not running (or dying due to a horrible running issue). the 'heavy load' timing and crazy amount of extra fuel associated a false high map reading would certainly cause a stumble.

    map sensors don't go bad often, you can test them by datalogging if you hook a mityvac or other hand operated vacuum pump up to it. log with key off while you slowly apply and release vacuum, then graph the result and make sure there are no drop-outs, and ensure it goes all the way from 10kpa to 100kpa.

    i doubt it's the sensor itself, though.

    a bad connection at the MAP sensor may cause issues, though, and sometimes doesn't show up as an error code. wiggling the connection while testing the sensor should make that show up.

    I just replaced this MAP but could it be faulty.
    so you had issues with the map sensor already? can you tell us how you arrived at that conclusion? or were you just taking a guess at something

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    Thanks Steveo, unless I have mistaken you for another person you had helped me via email awhile back tuning and you were kind enough to help me. I kept having odd logs that you were telling me something not right with motor and not the tune. You were spot on and I thank you for your helping me even when I was hard headed not listening. My MAF had odd readings and went SD. It has been a very fine running engine well for the first few days anyway. Until now going from MAF to SD was night and day. Not going into it but,,,,

    This issue with surging and stumble just came up as I mentioned. I have even went back to my "Safe SD Tune" a few times as a base just to be sure with same results. The MAP I recently installed I did so just because a friend had a brand new one in the box because mine looks very generic. The replaced MAP had no known issues and good eye by the way. I reinstalled the 1st MAP today with no changes. It runs great every time in open loop and as soon it goes closed stumble just like it's been doing. I can use Scan94/95 and lock it in OL and just like silk tho WOT suffers and yes I need WB O2s for several reasons.

    As you mentioned I believe it's rare a MAP will go bad much less 2. I tuned 10 degrees more advance at anything above 70kPa at 800 and 1000rpm cells just to test today. I know it's a new tune but just as normal it was great in OL and soon as CL comes in I can blip the throttle and it stumbles. What I don't get is in CL I blip the throttle to a quick 33% TP, kPa is 67, timing 30 and very responsive throttle . In CL I blip the throttle to 32% TP, kPa is 88.6, timing 30 and stumble. If I hammer the throttle in CL I could make the engine go dead I believe because it just falls on it's face like you hit a switch and slightly revs as I release the throttle. What causes this in CL only or am I approaching this wrong.

    I used your EE Tuning Thing today to play with trim and spark with no difference and I love the program BTW. I'm just lost and can't get my head around it. Only thing I can think is Open Loop AFR is correct and I'm way off on my VE Table but why was it great a few days ago or am I way off on this assumption. Just to add when I check SD Mode the MAP Cell Boundaries in Tunerpro RT are all zeroed out and I do change back to my original settings. I don't believe this is an issue and I think this is done so Cell Boundaries only use RPM for cell selection. I'm just getting more confused and I need help guys, thank you
    Last edited by troutdog311; 10-26-2015 at 05:00 AM.

  15. #15
    LT1 specialist steveo's Avatar
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    if it only does this in closed loop, then it's certainly related to your o2 sensors. you should make sure they're switching properly around stoich. sounds like you might have an o2 circuit problem or faulty o2. can you post a log, and point out when it's stumbling?

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