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Thread: Idle problem only in open loop mode?

  1. #1
    Tuner
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    Jan 2008
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    Idle problem only in open loop mode?

    If you guys remember I made a post a few weeks ago about my idle problem when I first start my car. The video below shows you what my car does at first. However sometimes the idle drops down too low when its doing that and stalls out.

    Check the video out again:
    Start Idle Problem Video

    I thought maybe it was something fuel related. When it would stall out and I would crank it over again it was almost like the car had no fuel? So I went ahead and installed another fuel pressure regulator and fuel filter. Now the car hasn't been stalling a few days so I have no idea if replacing those parts will help if it does stall again. However after replacing those parts the car still does the funny idle on startup.

    I scanned the car when i first started it and it ONLY seems to do this revving up/down while its only in open loop mode. ONCE it goes into closed loop the car idles perfectly?

    As soon as I started the car while still in open loop I noticed that the 02 was reading over 1000 and the LTFT go from 0.8 to 14.1. Now the LTFT goes up to a max of 14.1 while the Rpms are dropping. Then when the rpms start going back up it drops down to 0.8. Its a smooth travel between 0.8 and 14.1. I also notice that the map sensor starts going up right before the rpms revve up. Then the Map goes back down again right before the rpms start dropping.

    During normal operation temperatures the delay for the car to go into closed loop is 10 seconds. Right after 10 second is when the 02 sensors pulses on/off and the LTFT goes and stays at 0.8 and the idle is smooth?

    I have a feeling I need to make an adjustment to one of the tables in my Pcm for then the car is on open loop mode? Would I make any changes to the "Startup AFR Correction" while in Park/Neutral? Should I decrease the seconds till the car goes into open loop when its at operating temperatures?

    I have a scan of the car when it starts so if anyone would like to take a look at it let me know. I hope someone can give me a hand because this revving up/down at start is getting annoying.

    I also forgot to say that I have cleaned my Air filter and also the MAF sensor a few days after I cleaned the filter.
    Last edited by GeforceXtreme; 05-21-2008 at 10:03 PM.
    2000 Buick Regal GSE Ported Gen III SC with 3.0” Pulley, Northstar TB, ZZP Ported LIM, ZZP Stage III IC, Comp VS Cam, Comp 105 Springs, Viton Valve Seals, 42.5 Injectors, PRJ Gen II Fuel Rails and Racetronix Fuel Pump with HD Harness, TOG Headers with 3” Catted Downpipe, ZZP 3” Dual Stainless Cat-back, Dynotech Stage II Trans, 3.29 Final Drive, 2750 stall converter, GTP Engine Cradle Mounts, Front Motor Mounts Spun 90*, JMB 4” FWI, Autolite 104’s, 180* stat, GMPP Handing Kit, Moog Endlinks.

  2. #2
    Advanced Tuner
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    Dec 2007
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    Montreal, Quebec, Canada
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    Have you played with low RPM timing any?
    '99 Black GTP Sedan
    3.4-2.6" PB Quick Change pulleys, Custom CAI, XP Cam, N* TB, LQ4 MAF, SLP headers, 42.5# Injectors, 180/195* thermostat.

    13.501 @ 103.392 on 91 (2.4 60-foot).
    13.82 @ 105.28 on 87 octane! (2.42 60-foot).
    263kph top end as shown on the GPS.
    All this and 39MPG to boot. What more can a man ask for?
    * Just another enthusiastic amateur tuner! *

  3. #3
    Tuner
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    Quote Originally Posted by JerryH
    Have you played with low RPM timing any?

    Yup everything 1,200rpms and lower is back to stock. I think that is what helped the stalling problem. However it still does stall once in awhile I want to say more on cold wet nights?
    2000 Buick Regal GSE Ported Gen III SC with 3.0” Pulley, Northstar TB, ZZP Ported LIM, ZZP Stage III IC, Comp VS Cam, Comp 105 Springs, Viton Valve Seals, 42.5 Injectors, PRJ Gen II Fuel Rails and Racetronix Fuel Pump with HD Harness, TOG Headers with 3” Catted Downpipe, ZZP 3” Dual Stainless Cat-back, Dynotech Stage II Trans, 3.29 Final Drive, 2750 stall converter, GTP Engine Cradle Mounts, Front Motor Mounts Spun 90*, JMB 4” FWI, Autolite 104’s, 180* stat, GMPP Handing Kit, Moog Endlinks.

  4. #4
    Tuner in Training
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    I had a similar issue and I adjusted the good spark tables in the idle range to be no more than .5 differance from one cell to another. I also cleaned up the maf and made sure there was no large jumps there either. Shortly after that, it all went away.
    Mike (MOJO)

    2003 GTP, L36 swap, TOGs extremes, ZZP stage 3 heads, SSIC, ZZP Ported Blower, 3.0/3.2 pulley, XP hot cam w/ 105#, 42.5# injectors, N* w/ 85mm MAF, Meziere Water Pump.
    Need more info, follow link below

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  5. #5
    Tuner
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    Jan 2008
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    Eastern Pa
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    I think this problem has something to do with my Primary VE table. Because I started doing a VE tune yesterday and my car was doing the same revveing up and down just like it does when I start it. It has something to do with being in open loop and the primary VE settings
    2000 Buick Regal GSE Ported Gen III SC with 3.0” Pulley, Northstar TB, ZZP Ported LIM, ZZP Stage III IC, Comp VS Cam, Comp 105 Springs, Viton Valve Seals, 42.5 Injectors, PRJ Gen II Fuel Rails and Racetronix Fuel Pump with HD Harness, TOG Headers with 3” Catted Downpipe, ZZP 3” Dual Stainless Cat-back, Dynotech Stage II Trans, 3.29 Final Drive, 2750 stall converter, GTP Engine Cradle Mounts, Front Motor Mounts Spun 90*, JMB 4” FWI, Autolite 104’s, 180* stat, GMPP Handing Kit, Moog Endlinks.