Materials to Maintain Your ZHP IIIII Hand Protection IIIII Tools to Maintain Your ZHP
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  1. #1

    Idle is hunting, Lean LTFT

    I have a 2004 330i E46, I recently had my rear main replaced. Upon getting my car back I started to feel the idle hunting when warmed up. My first question is there anything he could have messed with around the transmission to cause a lean condition?

    Ive also replaced the thermostat, fuel filter (Which had a broken vac line), and cleaned out the ICV and MAF. Checked the DISA, still holding vacuum.

    When I changed the fuel filter I had the check gas cap light come on for a few miles, but went away. Figure its because its a fresh filter.

    Ive done a smoke test on the car and had a very small vac leak around the ccv but I dont think is big enough to cause -16% LTFT. I also think that leak has been there for awhile.

    Unplugged each coil one at a time to hear for a change, they all bogged down figuring they are all ok.

    Im getting a air rushing noise every time it hunts around the DISA valve or from under. Ive checked everything around there for cracks and leaks and everything checks out.

    Ive been banging my head against this for the last 48 hours.

    Fuses?
    Relays?
    Air in coolant maybe? (isnt overheating)
    Gas Cap?

    EDIT: I have zero codes.

  2. #2
    Join Date
    Jan 1970
    Location
    Liberty Township, OH
    Posts
    37,935
    We're these conditions present prior to the rear main being replaced? If the answer is No, take it back to the mechanic who performed the rear main seal repair.

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  3. #3
    It always had alittle bit of a idle issue, nothing this extreme though. Going lean is new, I replaced a bunch of stuff when I got it home so its hard to tell. I had a family friend do the rear main, I asked him about it and said it ran fine after he test drove it. So, not really sure who to believe I dont mind doing the work and figuring it out. Just need alittle bit of advice where to start without buying parts and start hucking them into the car.

  4. #4
    Join Date
    Dec 2010
    Location
    Fairfax Station, VA
    Posts
    2,806
    Two ideas:

    Open your gas cap, look at the rubber o-ring. If it's cracked (or missing), replace the gas cap immediately. It o-ring is intact, spray it with silicone spray and allow the silicone to settle in, hopefully it'll plump up the o-ring somewhat.

    On the small leak around the intake boots/DISA/ICV, when the idle stumble starts, spray around that area with carburetor cleaner. The liquid of the carb spray will temporarily seal up the vacuum leak, you'll hear the idle increase. Keep doing this until you can pinpoint the exact spot of the vacuum leak, then fix it.

    Bruce
    21 GMC Sierra - mine
    16 X5 M-Sport - wife
    11 M3 - 1st son
    04 Tundra - 2nd son
    17 X1 M-Sport - daughter

    Former (mo/yr sold):
    15 335xi M-Sport (8/18)
    11 335is (8/17)
    11 X5 AW/blk (11/15)
    04 330xi blk/gray (7/15)
    06 ZHP SGM/blk (6/15)
    08 335xi blue/blk (4/15)
    04 ZHPci MB/blk (2/14)
    04 ZHPcic IR/Alc (10/13)
    01 540iT anthra/blk (7/13)
    04 ZHPci TIAG/blk (9/12)
    03 540i M-Sport (9/12)
    01 325ci (3/12)
    02 325iT 5MT (10/11)
    05 ZHPci (7/11)
    03 330cic (2/11)
    00 323ci (10/10)

  5. #5
    Ill check that out on the gas cap.

    Intake boots are brand new and checked for cracks, all good. The grommet for the ICV is brand new too. Little hesitant about the carb cleaner around the alternator, Ive had a mechanic spray it around it before and it went up in flames pretty good.

    Is there anything below the CCV Oil Separator that could be losing vacuum?

  6. #6
    Join Date
    Dec 2010
    Location
    Fairfax Station, VA
    Posts
    2,806
    Sometimes, since you can't see 360 around it, the boots are not completely seated as you might think. On the spray, use anything, brake cleaner, even water. If there's a vacuum leak the leak is going to suck the liquid into the small gap and temporarily seal it for a couple of milliseconds. I suggested carb cleaner because it acts like ether and there is an immediate slight increase in the idle as it's receiving a richer fuel mixture, it's a dead give away.
    Last edited by BCS_ZHP; 04-14-2017 at 04:48 PM. Reason: Typo

    Bruce
    21 GMC Sierra - mine
    16 X5 M-Sport - wife
    11 M3 - 1st son
    04 Tundra - 2nd son
    17 X1 M-Sport - daughter

    Former (mo/yr sold):
    15 335xi M-Sport (8/18)
    11 335is (8/17)
    11 X5 AW/blk (11/15)
    04 330xi blk/gray (7/15)
    06 ZHP SGM/blk (6/15)
    08 335xi blue/blk (4/15)
    04 ZHPci MB/blk (2/14)
    04 ZHPcic IR/Alc (10/13)
    01 540iT anthra/blk (7/13)
    04 ZHPci TIAG/blk (9/12)
    03 540i M-Sport (9/12)
    01 325ci (3/12)
    02 325iT 5MT (10/11)
    05 ZHPci (7/11)
    03 330cic (2/11)
    00 323ci (10/10)

  7. #7
    I reinstalled those boots probably 5 times in the last 24 hours. Ill have to grab some carb cleaner and give it a go. I just have a real hard time believing that a small vac leak would cause -16% LTFT. What do I know though

  8. #8
    Join Date
    Dec 2010
    Location
    Fairfax Station, VA
    Posts
    2,806
    When you replaced the intake boots, did you replace the plastic "F" connector and the small vacuum line attached to it? If not, my guess is your leak is there. The dealer sells that "F" connector for about $3-5 and a 4-6" piece of vacuum line is like a buck.

    Bruce
    21 GMC Sierra - mine
    16 X5 M-Sport - wife
    11 M3 - 1st son
    04 Tundra - 2nd son
    17 X1 M-Sport - daughter

    Former (mo/yr sold):
    15 335xi M-Sport (8/18)
    11 335is (8/17)
    11 X5 AW/blk (11/15)
    04 330xi blk/gray (7/15)
    06 ZHP SGM/blk (6/15)
    08 335xi blue/blk (4/15)
    04 ZHPci MB/blk (2/14)
    04 ZHPcic IR/Alc (10/13)
    01 540iT anthra/blk (7/13)
    04 ZHPci TIAG/blk (9/12)
    03 540i M-Sport (9/12)
    01 325ci (3/12)
    02 325iT 5MT (10/11)
    05 ZHPci (7/11)
    03 330cic (2/11)
    00 323ci (10/10)

  9. #9
    I never took off the F connection, I replaced that smaller vac line that runs down to the fuel filter aswell, Well just the ends of that line.
    The only things that have changed since it last ran fine was...
    -Thermostat / Bleed
    -Fuel filter
    -Cleaned MAF, ICV, DISA
    -Rear Main
    -Brake Rebuild / Bleed


    Figure I can check that gas cap and just double check all the spark plugs for fouling.

  10. #10
    Looking at it the fuel trims while driving I noticed that while driving I hover in the -.2% to 3% LTFT on both banks. However when I sit at a light or stop sign "LT FTRM1" goes to about 3-4% and "LT FTRM2" goes to about 15-22%.

    Bare with me but if I understand this correctly my o2 is picking up that bank 2 LTFT is rich?

    Would this be spark plugs / injectors?

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