Bad AFM = Bad Idle?

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Thread: Bad AFM = Bad Idle?

  1. #1
    SupraForums Member
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    Bad AFM = Bad Idle?

    My car hasn't been running in over a year (blown engine), but she's finally back. My car runs great while cruising/WOT but at idle it runs shitty especially when its colder out. Its been cold the last few days and it was idleing bad but today it was like 65 and it idled good until tonight when it got cold again. Ive checked tps, isc, boost leaks, timing. Also my boost guage reads like -15 when it idles bad but when idling good it was reading -18. Could this be a faulty AFM?? or something like a fuel pump.

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    nobody?

  3. #3
    slowly giving up...
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    stop all the speculation and check your codes. that way, you'll know for sure.

    -shaeff

  4. #4
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    ya, no codes thrown. forgot to mention that. it did the same thing again today, ran good when it was nice out but not good when it was colder and raining this morning.

  5. #5
    Destroyer of Turbos MKIIINA's Avatar
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    bench test the electronics per the tsrm. i just got done testing my old aft to see if it was good or not and it passed!

  6. #6
    Ask First Search Later mysupra87's Avatar
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    Cold Start Injector maybe?
    MKIII FAQ SECTION <CCCCCLLLLLLIIIIIIIIIIIICCCCCCCCCCCKKKKKKKKKK

  7. #7
    This Is Why I'm Hot..... Larry_A's Avatar
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    Quote Originally Posted by mysupra87
    Cold Start Injector maybe?
    Hello mysupra87,
    No. The CSI only functions during cranking. And your sig reveals a jaded attitude, but I won't go anymore OT than that.

    blu87sup,

    Bad AFMs almost always trip an ECU code: 24, 32, & 34, IIRC. Given the next sentence, let's eliminate the AFM. Since the symptoms do not occur during cruise/WOT and there are no ECU codes, let's look at the items that affect idle, yet do not yield a code when malfunctioning. Hmmm.

    1] Check the coolant temp sensor input to the ECU, which is more or less a toggle for TCCS open loop going to closed loop upon warm-up. It could have some bearing to the symptoms you describe*. The sensor itself is on the t-stat cover area [check TSRM for your year details]. I have repaired countless faulty wires on many Supras in this area, so make sure all wiring/connectors are sound. FWIW, *I do not think this is the problem.

    2] The Idle Speed Control valve [ISC]. Since the engine does run, let's assume the ISC is functioning, but not at 100%; so, let's not do the TSRM electrical checks on the valve at this point. The ISC is on the intake plenum, which has the propensity to get gunked up from recircirculated EGR/crankcase vapors. Pull & clean the ISC. Also, the "wagon wheel" rubber flapper valve between the ISC & the intake plenum often gets petrified and/or gunked up, too. Clean the rubber flapper valve & make certain the rubber is intact & capable of sealing. Replace, if deemed necessary.

    That's all I have time for, for the time being.

    Good luck

  8. #8
    slowly giving up...
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    larry, his sig is actually because of a thread that i posted in. (i was in a very bad mood, actually, but i digress)

    blu87sup- did you actually check the codes? or did you just look for an illuminated CEL? lots of times the CEL will not light up when you have a problem. you'll feel the effects, but you'll only know for sure if you actually jump the diagnostic box.

    other than that, listen to larry, he's the man.

    -shaeff

  9. #9
    SupraForums Member
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    ya, i checked codes there are none. im pretty sure he is right b/c i had the ecu temp sensor broke but i ghetto rigged it so the car would start better. im heading to the j-yard right now to try to get a good one.

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