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2k Rpm Idle On My Rb20det....

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I had the AFM fail a couple of weeks ago (intermittent engine cut, 10.5:1 AFR) and finally replaced it last weekend.

Car was running fine until Thursday when it had a sudden power loss for an instant, which was repeated yesterday on the way home. When I stopped at home it stalled and on restart the idle shot up to ~2k rpm. Left it overnight, and had a play today .

- ECU is showing no new faults.

- On startup the idle shoots to 2K rpm, AFR at 14.7:1 after about a minute

- If I disconnect the AAC the idle drops to normal.

- Once fully up to temp, the idle drops back to ~ 900 rpm (after say... 6-7 minutes).

- If I restart the car again, I'm back with the 2K rpm idle.

- temp sender appears to be O.K. (I tried a spare).

- Under boost (~13psi) AFR is 12.2:1, which is around what it used to do before the AFM replacement.

Any suggestions? The ECU is an RB20DET manual ECU (supposedly anyway - it's a 23710-04U00), but the loom (from an auto) isn't fitted with a Consult plug (although there is a connector which has the appropriate RX/TX wires running to it).

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Ah - the TPS! I've had intermittent TPS errors for years, so hadn't bothered to consider that. But that's what the problem was - the idle switch wasn't closing properly anymore. Quick adjustment, and now it's all working correctly.

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awww no fair, wish mine was that easy.

the idle shot up another 300rpm after i put some cylinder cleaner through it. Perhaps carbon deposits blocked the leak a little

Its easy to engage the twin plate with the higher idle..thats about the only upside i see lol

Oh well, its getting fixed next week :D

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  • 1 month later...

to fix the tps you undo the adjuster screws just enough so you can adjust the angle (clockwise/anticlockwise) of the tps until the idle is right. But be careful, theyre only minor adjustments and if you move it too much then it might take a little bit of fiddling to get correct again.

you can check the TPS signal as being 0%( or volts?) as correct on a Power FC controller or if you have a consult cable

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your resting tps volts should be between 0.3 and 0.4 volts. any less and you get this lag effect, any more and your car revs higher. and the wire to test is on the plug attached to the small length of wire coming out the bottom of the tps, not the one on the side. thats your throttle on off switch.

its the middle wire i think, one will be ground, one will be 5v and the other variable (thats the one).

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