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Thread: Very lean at idle RPM/MAP problem

  1. #101
    Senior Member WicketMike's Avatar
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    so maybe its lean because i have the COT turned off? does the COT turn on at start up?

    98' White TA A4 TSP 231/237 PP Stage II 59cc heads
    401rwhp (unlocked) 1.594 60'-11.60 e.t.-116.98 mph
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    98' Sport Gold Metallic TA M6 - 13.39 e.t. Bone Stock
    My Trans Ams
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    2006 Chevy Monte Carlo SS 5.3L LS4 (wifes car) stock (for now)

  2. #102
    Lifetime Member eboggs_jkvl's Avatar
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    Quote Originally Posted by WicketMike
    so maybe its lean because i have the COT turned off? does the COT turn on at start up?

    COT is to protect the CATs when you are running too lean. COT adds gas when you are WOT and start to lean out.

    E
    2014 Corvette Convertible, Torch Red, A6, Z51, 3LT, NPP Exhaust



  3. #103
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    Default Not really lean?

    Quote Originally Posted by jfpilla
    MarcinK,
    My lean condition, in SD, only happens when the car is started cold. The AFR is exactly 18.62 and if I let it idle to 84C* it will then track Commanded. These numbers are consistantly the same regardless of how I have set the main fueling tables. I looked at logs going back a year. It's real hard to figure since 18.62 is observed, at startup, regardless of IAT and ECT as long as it's 50* and below(the only logs I have). At 80*and over commanded is always used. The immediate tracking of Commanded at 84* is also confusing. It sure seems like something is controlling these changes. I also replaced my battery 2 weeks ago and have not seen any difference. Voltage at start-up varies a lot. It seems to be lower and creeps up slowly when it's very cold out. other times it's right on 12V and goes right to 14.1.
    Also, it's not VE's. The same cells produce correct AFR when warmed. As before, I'm lost and will stay with the MAF.
    Joe
    I can't see how a cold engine would hardly run that lean (18+ AFR).
    Could it be that the WB is giving a lean reading because of the air injection pump is causing the false reading for the first few minutes until it shuts off.
    I removed mine and I don't have a lean start.
    Just a thought, Curt
    99C5, mn6, Vortec T trim, Snow meth injection, AFR 205s, ARP studs,Comp 224*112*+2*.580", YellaTerra RRs, PRC Ti's w/dbls, Supermaxx LTs, No Cats, Corsa Indys, LS6Intk, Hurst, Fikse Aro18"s. Pilot Sports 315/30,265/35, 04ZO6 Shocks Hotchkis bars, EBC YellowStuff pads, SS hoses, LM-1, EFILive, 2002 OS. RPS dual disc Clutch, DTE Strut Brace & output shaft.

  4. #104
    Guess who's back!!!! Black02SS's Avatar
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    Quote Originally Posted by curtbriggs
    I can't see how a cold engine would hardly run that lean (18+ AFR).
    Could it be that the WB is giving a lean reading because of the air injection pump is causing the false reading for the first few minutes until it shuts off.
    I removed mine and I don't have a lean start.
    Just a thought, Curt
    Quote Originally Posted by Black02SS
    I don't think this has to do with IAT to be honest. I have found that I will see a lean condition if I have been driving the car and then stop it, wait about 5mins, start her up again and it does the same thing with the motor hot.
    That was my post from earlier in the thread.

  5. #105
    Lifetime Member jfpilla's Avatar
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    Quote Originally Posted by eboggs_jkvl
    If you want to disable the AIR, wouldn't the B0204 set to 1 RPM be the catch all that would work? My AIR & EGR are in the attic and I've put all of the codes to sleep. Would I need to set this to stop the AIR from inducing action in the PCM? Right now, it is set at 2825 RPM. It may be appropriate to set B0205 to 1 too.


    Elmer
    It appears there are at least 5 ways to disable the pump.
    If you're concerned turn it off.
    2003 red vert
    Mods:
    LS7 crate engine, wet sump, 24xx reluctor
    LPE 100mm MAF
    Vararam, cold air intake and bridge
    RPM Level 6/4L60e trans
    3.42 gears
    Yank SS3600
    1-7/8" AR headers
    Z06 exhaust
    470rwhp 437rwtq
    1/8th mi-1.526-60'-6.862-1/8th-@100.74mph

  6. #106
    Lifetime Member jfpilla's Avatar
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    Quote Originally Posted by curtbriggs
    I can't see how a cold engine would hardly run that lean (18+ AFR).
    Could it be that the WB is giving a lean reading because of the air injection pump is causing the false reading for the first few minutes until it shuts off.
    I removed mine and I don't have a lean start.
    Just a thought, Curt
    I reached that conclusion in post #96, after reading HPcubeds'.
    Last edited by jfpilla; January 29th, 2006 at 12:25 PM.
    2003 red vert
    Mods:
    LS7 crate engine, wet sump, 24xx reluctor
    LPE 100mm MAF
    Vararam, cold air intake and bridge
    RPM Level 6/4L60e trans
    3.42 gears
    Yank SS3600
    1-7/8" AR headers
    Z06 exhaust
    470rwhp 437rwtq
    1/8th mi-1.526-60'-6.862-1/8th-@100.74mph

  7. #107
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    Talking

    Quote Originally Posted by jfpilla
    Vetpet
    The AIR Pump injects air into the manifolds to accelerate burning of the richer fuel created by added fuel for start up, less than efficient burning by a cold engine and the cats not being hot enough to clean the gases emitted. This process probably helps the cats heat up too. As for an Airflow reading at start up, if you have an AIR pump, it will look lean. Mine is 18.62:1, or so, with no MAF. With the pump disabled, it's a mess for a short time and then follows commanded. I don't see any useful A/F #'s before it goes to commanded. It might be my WB 02 is lazy, though. I've had it a while.

    Let me add, if the pump is on with the MAF, it should be lean for a bit.

    Your not a newbie. No more self deprecation please. Be .
    Joe
    Thanks for the encouragement Joe. Since I haven't gone through the actual hands on tuning yet I can't put myself in the same league as the rest of you guys. I'm just trying to put stuff I've read into the context of these discussions and see if I've understood what I've read. I enjoy these discussions and the different ways that people attack the problem. Many heads are better than just one.


  8. #108
    Lifetime Member jfpilla's Avatar
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    Quote Originally Posted by VetPet
    Thanks for the encouragement Joe. Since I haven't gone through the actual hands on tuning yet I can't put myself in the same league as the rest of you guys. I'm just trying to put stuff I've read into the context of these discussions and see if I've understood what I've read. I enjoy these discussions and the different ways that people attack the problem. Many heads are better than just one.

    I'm impressed by the time and effort you're putting in to learn.
    2003 red vert
    Mods:
    LS7 crate engine, wet sump, 24xx reluctor
    LPE 100mm MAF
    Vararam, cold air intake and bridge
    RPM Level 6/4L60e trans
    3.42 gears
    Yank SS3600
    1-7/8" AR headers
    Z06 exhaust
    470rwhp 437rwtq
    1/8th mi-1.526-60'-6.862-1/8th-@100.74mph

  9. #109
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    Quote Originally Posted by jfpilla
    I reached that conclusion in post #96, after reading HPcubes'.
    Joe, I read your post #50, replied and went to bed, guess I should have stuck around.
    99C5, mn6, Vortec T trim, Snow meth injection, AFR 205s, ARP studs,Comp 224*112*+2*.580", YellaTerra RRs, PRC Ti's w/dbls, Supermaxx LTs, No Cats, Corsa Indys, LS6Intk, Hurst, Fikse Aro18"s. Pilot Sports 315/30,265/35, 04ZO6 Shocks Hotchkis bars, EBC YellowStuff pads, SS hoses, LM-1, EFILive, 2002 OS. RPS dual disc Clutch, DTE Strut Brace & output shaft.

  10. #110
    Lifetime Member jfpilla's Avatar
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    Quote Originally Posted by curtbriggs
    Joe, I read your post #50, replied and went to bed, guess I should have stuck around.
    Nick Williams told me weeks ago that it was probably the AIR Pump. I should have tried it back then.
    When HP Cubed posted, it suggested I should try it. It's easy enough.
    2003 red vert
    Mods:
    LS7 crate engine, wet sump, 24xx reluctor
    LPE 100mm MAF
    Vararam, cold air intake and bridge
    RPM Level 6/4L60e trans
    3.42 gears
    Yank SS3600
    1-7/8" AR headers
    Z06 exhaust
    470rwhp 437rwtq
    1/8th mi-1.526-60'-6.862-1/8th-@100.74mph

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