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adjusting TPS without BAC/thermo

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Old 01-12-18, 03:36 PM
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adjusting TPS without BAC/thermo

Is there any information about how the ECU interprets TPS data? I disabled thermowax, removed BAC and adjusted idle to 1.3k using screw that controls opening of throttle plates. So the TPS should say 1V when idling on 750 RPM or it just means the throttle pedal not pressed and should be adjusted to real (1.3k in my case) idle?
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Old 01-12-18, 04:45 PM
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AFAIK the tps setting doesn't change with those items removed, the stock ECU till expects to see 1V (when HOT)

The BEST way to do it is dig out the ECU, put your voltmeter on the pin and have someone turn it for you until you get you 1V, that way you can bypass any old crinkly wires that may be adding extra resistance.
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Old 01-12-18, 06:48 PM
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What do you mean you adjusted the idle to 1.3k? Setting the TPS is simple. Either make up a test light and use that method (search) to adjust it to where only one light bulb illuminates, or back probe the TPS connector itself and adjust to 1 volt. Either method requires a fully warmed up engine and properly set idle and ignition timing to be precise. Actually drive the car a few miles to warm it up, not just idle. If it is a series 5 make sure you probe the right sensor.

Make sure idle adjust screws are all set properly before setting TPS. To a lesser extent, the ignition timing can change your results.

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Old 01-13-18, 10:05 AM
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Without the thermowax you don't need to warm up the engine or disengage the cold start cam when setting the TPS. That is the only difference.

Why remove the BAC? Put it back and you'll enjoy a car that idles.
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Old 01-13-18, 03:24 PM
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I have a crazy rev bouncing at about 1.5k rpms but cant figure out what component causes it. So completely disassembled throttle body, cleaned and resealed by the way removing unnecessary components. But that mazda idle system.. The only adjustable things left are crank angle, TPS and mixture screw.
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Old 01-13-18, 07:13 PM
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Originally Posted by wongfei View Post
Is there any information about how the ECU interprets TPS data? I disabled thermowax, removed BAC and adjusted idle to 1.3k using screw that controls opening of throttle plates. So the TPS should say 1V when idling on 750 RPM or it just means the throttle pedal not pressed and should be adjusted to real (1.3k in my case) idle?
AFAIK and anyone correct me if I'm wrong but the TPS should give the ECU a variable range so it can know what 3 states it should be in. Idle, Driving and then WOT.

If you adjust the throttle plates using the set screw but then set the TPS back to 1v you are in essence tricking the ecu since it thinks the throttle plates shouldn't be open and letting in as much air as they are which could cause problems.

Your stock ECU is programmed to only think the throttle plates are in a specific position and for other system to help it out at idle including the BAC and ACV.
FSM for throttle body adjustments
This is for the turbo s4 but if you're NA or s5 here's a link where you can look yours up RotaryHeads.com - 2nd Gen RX-7 PDF Technical Manuals FC3S

The car should be idling at 750 when the TPS reads 1v and NOT something else because that reading tells it the position and therefore amount of air you're letting into the car at the given time since the BAC and ACV ONLY work in idle state so if you're "idling" but the car thinks your not in idle state it wont activate the other systems used to assist in idle.
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Old 01-14-18, 10:34 PM
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I'd like to add if your idle is high and bouncy, you have a vacuum leak......more then likely at your BAC blockoff plate
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