Results 1 to 19 of 19

Thread: Engine not returning to idle smoothly in 69 Camaro LS1 Swap

  1. 08-28-2017 #1
    ryanater
    ryanater is offline
    Tuner in Training
    Join Date
    May 2012
    Posts
    39

    Engine not returning to idle smoothly in 69 Camaro LS1 Swap

    I have been dealing with this problem for a year now on my 98 LS1, and nothing I do seems to fix it. Also keep in mind that I have swapped heads, intake, and throttle bodies all while this problem remains constant.

    When I rev the engine, or come back down to idle when coming to a stop light etc. the engine almost dies. Usually it catches itself, but sometimes it dies. If the engine does catch itself, it will then stable itself out. If I let it idle without reving it up, it will idle all day without a problem. It's just returning to idle where I have the problem. It also seems like the problem gets worse the higher I rev the engine.

    Looking at the log, there aren't any obvious signs as to what is causing the problem. The IAC position is returning to the normal spot, and the spark advance seems to be ok.

    *new issue* A new issue that has appeared in the last week is that when I start the car up, the IAC position hangs at 0 for a couple minutes until it shoots up to about 140. I have to keep the car running with the throttle or it will die. I've also noticed that the IAC position is barely moving when I rev the car up.

    Take a look at the log and tune. The AFR isn't perfect and the MAF is switched off because I just made some engine changes, but I was having the same problems when I had the VE tables dialed in and the MAF turned on. I just haven't had time to get the wideband out and tune it again since the changes.

    MODS: Stock LS1 bottom end. LG G5X3 Cam. PRC Stage 2.5 5.3L Heads. FAST 90 Intake/90mm TB. Kooks Headers.
    Attached Files Attached Files
    Reply With Quote Reply With Quote
  2. 08-28-2017 #2
    5FDP
    5FDP is offline
    Tuning Addict 5FDP's Avatar
    Join Date
    May 2012
    Location
    Rogers, MN
    Posts
    13,565
    Without the MAF dtc's set to fail on first error you are not running in speed density correctly.

    The fuel trims are still showing that your VE and MAF are way off and need much attention still.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.
    Reply With Quote Reply With Quote
  3. 08-28-2017 #3
    ryanater
    ryanater is offline
    Tuner in Training
    Join Date
    May 2012
    Posts
    39
    Thanks for the feedback on the MAF DTCs. I'll make sure to fix that this weekend. And you're right that the VE table needs to be retuned. But again, I had them reasonably close earlier this year with the same idle problem.

    Would it help if I addressed the issues above and posted a new log next week?
    Reply With Quote Reply With Quote
  4. 09-09-2017 #4
    ryanater
    ryanater is offline
    Tuner in Training
    Join Date
    May 2012
    Posts
    39
    Ok so I finally got around to tuning my VE tables after an intake/TB/MAF swap. I'm still having the same exact problem. I even bought a new IAC valve with no luck.

    I'm attaching the log and new tune.

    RyanCamaro-9-3-17.hpt
    9-9-17 Idle.hpl
    Reply With Quote Reply With Quote
  5. 09-09-2017 #5
    5FDP
    5FDP is offline
    Tuning Addict 5FDP's Avatar
    Join Date
    May 2012
    Location
    Rogers, MN
    Posts
    13,565
    Have you used any of the idle tuning threads out there to help resolve the issue?

    Here is one write up and a config file set that most people use.

    https://www.hptuners.com/forum/showt...l=1#post424042

    https://drive.google.com/file/d/0Bwx...ZVQjNRdVU/view
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.
    Reply With Quote Reply With Quote
  6. 09-10-2017 #6
    ryanater
    ryanater is offline
    Tuner in Training
    Join Date
    May 2012
    Posts
    39
    I have used that guide before. And the idle worked great before I started having this problem.

    I will admit, I hadn't run through this config for a while, so I made sure to go through it again today and adjust my RAF, Idle Spark, and Throttle Cracker settings.

    Unfortunately, it didn't seem to help. I'm attaching a new log showing the same thing happening. However, this time I tried locking the timing and IAC position with the VCM scanner. Same thing happens...

    You can see from the log that the first 2 revs I don't have the IAC or spark locked, but the second 2 revs they are both locked. Very little difference in the engine coming down from high RPM. All 4 times it stumbles.

    *Another interesting thing that I noticed is that the idle spark should be set to 20 degrees, but the scanner is picking up 22 degrees. Not sure which modified is doing this.

    Any ideas??

    RyanCamaro-9-10-17.hpt9-10-17 Idle.hpl
    Reply With Quote Reply With Quote
  7. 09-10-2017 #7
    ryanater
    ryanater is offline
    Tuner in Training
    Join Date
    May 2012
    Posts
    39
    I was thinking about it and thought it may have been my injector tables were wrong after swapping injectors to the 36lb GTP injectors. To test this, I copied my stock injector tables over and tried running the car again. Didn't solve the issue...

    I'm thinking either a spark modifier table or a mechanical problem (I've searched for vac leaks).
    Reply With Quote Reply With Quote
  8. 09-11-2017 #8
    ryanater
    ryanater is offline
    Tuner in Training
    Join Date
    May 2012
    Posts
    39
    I tried multiplying the throttle follower decay tonight by .4 both in park and in gear. This seemed to help a lot, but didn't solve the problem.
    Reply With Quote Reply With Quote
  9. 09-12-2017 #9
    bdoobie69
    bdoobie69 is offline
    Tuner in Training
    Join Date
    Jun 2016
    Posts
    24
    I have a 2000 LS1 with a 228R and the 36lb GTP injectors. Mine runs fine with the settings attached. Yours seem to be different. Not sure if that is it or not.

    Default inj pulse.txtFuel to wall impact factor.txtIFR modifier vs volts.txtIFR.txtMin pulse.txtOffset.txtShort pulse adder.txt
    Reply With Quote Reply With Quote
  10. 09-12-2017 #10
    ryanater
    ryanater is offline
    Tuner in Training
    Join Date
    May 2012
    Posts
    39
    Thanks! I will try those tables as well and see if it changes anything.

    However, I'm starting to think it is an IAC area/Throttle Follower issue.

    The idle is fairly rock steady except when it dips down coming back to an idle. I think the WARR 92MM throttle body has a different IAC passage size and needs to be accounted for in the IAC effective area and throttle follower. I will play with those values later this week and post an update on whether that fixed it.
    Reply With Quote Reply With Quote
  11. 09-19-2017 #11
    ryanater
    ryanater is offline
    Tuner in Training
    Join Date
    May 2012
    Posts
    39
    I tried modifying the injector tables with no luck. I even tried swapping back to my stock injectors and it's still stumbling coming back down from idle.

    I was able to sort of fix it with the throttle follower table, but only by basically making the RPM hang coming back down. I think this might be putting a band aid on the problem rather than addressing the issue.

    One question. If I unplug the IAC motor, should the motor come back down to an idle without stumbling? I tried, this and it does still stumble.
    Reply With Quote Reply With Quote
  12. 09-19-2017 #12
    Area47
    Area47 is offline
    Senior Tuner
    Join Date
    Apr 2007
    Posts
    1,104
    throttle cracker mph set to 120, disable 200. try again.

    whats the tps voltage set at?
    whats the iac counts at idle, no fans at 190 degree's?
    The most hated, make the most power.
    93 Ranger. 5.3 D1X. 1069hp.
    Reply With Quote Reply With Quote
  13. 09-19-2017 #13
    ryanater
    ryanater is offline
    Tuner in Training
    Join Date
    May 2012
    Posts
    39
    I'm out of town now so I won't be able to try it until this Friday. However, if I unplug the IAC motor it stumbles about the same as if I had it plugged in.

    At 190 degrees, the IAC counts are usually between 25-29 and TPS voltage is .31V.
    Reply With Quote Reply With Quote
  14. 09-28-2017 #14
    brycedrue
    brycedrue is offline
    Tuner in Training
    Join Date
    Oct 2013
    Posts
    34
    Looks like your TPS voltage is low. I think it should be in the neighborhood of .50 volts closed
    Reply With Quote Reply With Quote
  15. 09-28-2017 #15
    ryanater
    ryanater is offline
    Tuner in Training
    Join Date
    May 2012
    Posts
    39
    What would that do? If it's too high, it won't go to idle tables. What happens when it's too low?
    Reply With Quote Reply With Quote
  16. 10-08-2017 #16
    ryanater
    ryanater is offline
    Tuner in Training
    Join Date
    May 2012
    Posts
    39
    Hey guys. I'm still at a total loss on this one. Attached is one more log that has the wideband hooked up. It shows the AFR is still remaining pretty constant coming back down from idle.

    I tried playing with the throttle cracker and follower. Both helped, but I had to make the engine come back down from idle extremely slow in order to help the problem. So I don't think that is the root cause anymore.

    Any ideas?10-8-17 V2.hpl
    Reply With Quote Reply With Quote
  17. 10-08-2017 #17
    ryanater
    ryanater is offline
    Tuner in Training
    Join Date
    May 2012
    Posts
    39
    On a side note. I did notice that the throttle body was sucking a couple of drops of oil into the intake when coming back down to idle. I wouldn't think it would be enough to do anything though.

    However, there is quite a lot of oil buildup in the intake.
    Reply With Quote Reply With Quote
  18. 10-19-2017 #18
    ryanater
    ryanater is offline
    Tuner in Training
    Join Date
    May 2012
    Posts
    39
    It might be worth starting a new thread at this point, but I fixed the oil consumption through the PCV and that wasn't the problem.

    SO, I am a little closer though!! I found that both my injector pulse width and Dynamic air are different when idling smoothly and returning to idle. About 95lb/hr when idling normally and 80lb/hr when returning to idle. The injector PW is about 2.6ms-2.7ms when idling and around 2.1ms when returning to idle.

    I think I'm close to figuring out what is going on, but I don't know what would be causing this difference.

    I tried adding fuel to the cells that go lean when returning to idle in my primary and secondary VE tables, but it didn't seem to make a difference. Is there a table that overrides the VE table when returning to idle?

    And yes I know my LTFT's are off again, but I was using the new injector data given to me earlier in this thread. As seen before, I had my LTFT's within 5% and it still didn't help.

    One last thing to notice is that when I barely crack the throttle (.4% TPS) when returning to idle I don't seem to have the problem.

    All 3 pictures below show my scenario with the IAC position locked.
    Normal Idle.JPG
    Idle Return 900RPM 0TPS.JPG
    Idle Return 900RPM.JPG

    Log attached...

    10-19-17.hpl
    Last edited by ryanater; 10-19-2017 at 11:46 PM.
    Reply With Quote Reply With Quote
  19. 11-12-2017 #19
    ryanater
    ryanater is offline
    Tuner in Training
    Join Date
    May 2012
    Posts
    39
    SOLVED!!!!

    First of all I replaced the PCM with an 0411 PCM from a 02 Camaro. The new PCM seemed to react much faster and helped a lot.

    The big difference was that I finally figured out how to dial in the IAC effective area so that desired idle air matched dynamic air. This didn't solve the problem in itself, but with the new throttle body the PCM didn't know how much airflow was being added by the IAC valve.

    Once I had the IAC effective area dialed in, I simply increased the throttle follower and cracker airflow and delay to set the engine back down to idle softly. It took a lot of tweaking, but I ended up tripling the values in the throttle follower to prevent a stumble. The idle comes down a little slower than I would like, but that's probably just something I will have to deal with considering I have a large cam, FAST intake, and a lightweight 8" clutch.

    Big shout out to the guys in the HPTuners booth at SEMA. They spent a fair amount of time walking me through potential issues and thinking of solutions. Also appreciate all of the help on this forum!

    The weather is crappy here in Seattle so I still haven't taken the car out to really make sure I haven't caused any driveability issues, so I'll post back if it comes back
    Reply With Quote Reply With Quote
« Previous Thread | Next Thread »