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2001 corolla po171..

This topic contains 12 replies, has 3 voices, and was last updated by Avatar tim brown 10 months ago.

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  • #893286
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    tim brown
    Participant

    Hi guys. I have watched a ton of your videos and loads others and still stuck. i am working on a 2001 corolla.1.8l..174,000 miles. code is a po171..lean bank 1. I have high fuel trims. shrt sometimes maxs out at 19.5% and lngt is always high 15 to 20 % +. Trims will drop at 2500rpm…maf reading about 1.8 at idle and rises up to 8 or 9 at 2500rpm. I have done a smoke test and could not detect a leak. o2s b1 wave looks ok, average about .485, and does switch wave from .1 to about.800…I dont think its fuel delivery because the trims drop at higher rpms. . vacuum tested about 21 with needle bounce, possible valve guides leak?
    Freeze frame showed Fsystem..cl…ECT 179Deg,,, shtft -2.2,,, lgtft 34.4%,,,rpm, 710,,,,,IAT 95Deg,,,
    I am about to start throwing money at it. not sure what else to do. i need the car fixed to pass emmisions for my daughter to start college. Live in tx and have to pass emmisions. Looking at new maf,o2sensors. Already changed pcv and air filter and cleaned the maf.Help !!

Viewing 12 replies - 1 through 12 (of 12 total)
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  • #893293
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    Billy
    Participant

    What are the fuel trims at 3000-4000 RPM? How did you smoke test?

    #893295
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    tim brown
    Participant

    I made a smoke machine and got tons of smoke. Only leaks i could find was around the plenum before the m.a.f.( fixed them anyways).. I was tapped into the brake booster line. When the booster was plugged in i could pump the brakes and no numbers changed. Vacuum test on the booster was steady and no let down after an hour.
    Trims as follows. key on ing off shrtft1 0.0… longft1 14.1%….ect 59Deg..
    warmed up to 178deg…. rpms at 3500..shrtft1 -1.6,, longt +1.6… several readings were just about even st -2.6,,, lont +2.6.. pretty close to even shrt and longt..sure does look like leak to me, but cant find it..i can make tons of smoke too.. i even bypassed the intake and went to the throttlebody, no smoke anyplace..

    #893296
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    Billy
    Participant

    Any differences in the idle trims between hot and cold engine?

    #893297
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    tim brown
    Participant

    Not really
    About the same..

    #893299
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    Billy
    Participant

    My guess is a leak on the underside of the intake manifold gasket that’s diffusing the smoke before you can see it. Leaks from the old black gaskets on those cars are so common, it’s almost impossible not just to assume that’s the problem.
    There are gasket locator tabs at the top outer corners of #1 and #4 that you can see with the engine cover removed. If those tabs are black, not orange, I’d go ahead and replace that gasket with the new orange one.

    #893300
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    tim brown
    Participant

    Thanks..I figured it would be something I had not guessed.. for less than $20. It’s worth a try anyways..I will update after the repair..

    #893347
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    tim brown
    Participant

    HI.. Made no difference. The gasket looked good upon removal..still stuck on same problem..

    #893355
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    Billy
    Participant

    Well shoot. Then I agree MAF sensor and upper O2 sensor are the best candidates, but given the trims drop at higher RPM, they’re not very good candidates.
    Air filter is OEM equivalent, not high flow, correct?

    #893371
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    tim brown
    Participant

    oem air filter.. Doesnt make any sense does it. Sure does act like a leak but i can not find it. Did another smoke test, have tried propane and brake cleaner with no luck.

    #893396
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    Its me
    Moderator

    MAF will cause this issue. You can try cleaning them, but Toyota does not recommend it. Also, if you do try to clean the MAF, the red bulb is not the wire to clean (That is the Intake Air Temperature sensor (IAT). The part that needs sprayed is the wire down in the middle.

    Also The issue with the leaking air on the intake manifold gasket was for 2003+ Corollas when they changed to a plastic intake and the gaskets were plastic/rubber. The 1998-2002 intakes were a fairly stout aluminum and the gaskets were metal.

    Good luck

    -Karl

    #893398
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    Billy
    Participant

    My bad. Thanks Karl!

    #893426
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    tim brown
    Participant

    Thanks… I already cleaned the maf. And i did clean the correct area, ordered a new one but it was defective, figures,..When i pulled off the intake manifold it looked good but replaced the gasket anyways, it was the aluminum manifold. Waiting for the replacement maf then i will update..

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