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Throttle Butterfly Valve Inop

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I have a 2000 Boxster that I have just taken out of storage. The car won't rev above 2000RPM.

I hooked the car up to a scantool and determined that the engine revs were actually caused by the timing advancing when I give the car gas, and not the throttle opening.

I confirmed this by unhooking the plug at the throttle body and running the car with the same results.

When I check for power on the pins that control the throttle butterfly valve (at the throttle body) I read 0Vs regardless of pedal position, except for a quick Voltage burst when I turn the key on.

I do not have a wiring diagram yet for this car, and I assume there is a potentiometer at the pedal that controls the valve. IS there a dedicated potentiometer that controls the throttle opening? I find it odd that the timing changes when I "accelerate" but there is no power at the throttle body.

I have started the car a few times this year, with no issues with reving. Any thoughts?

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When you say rev is this parked or moving? If parked is the car a Tiptronic?

I does it when moving and parked. The car is a 5 Spd and will move enough to get it in and out of the shop.

And Hello to all!

Edited by Dragthis1
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  • Admin

Two things come to mind -

- the car has slipped back into delivery mode which limits the speed (and revs) - if this is the case you will need a PST2 or PIWIS tester to reset it.

- you likely will need the Durametric software, a PST2 or PIWIS tester to test the throttle position sensor.

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The Throttle position sensor is working, when manually force the butterfly open and watch the tps readout on the scantool it detects the throttle position. Does delivery mode cause the throttle not to opperate at all? I don't think you would be able to move the car on any type of incline, so I doubt that it is in delivery mode....mind you this is the first I have heard of delivery mode!

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If the throttle sensor is working then I would suspect the MAF - although MAF problems usually cause rev problems at 4000 RPM and up.

For a quick test you could disconnect the MAF and see if you can get to about 4000 RPM before it stumbles.

I tried the MAF the car still would not rev up and then it stumbled.

I also have a P1502 Manufacturer Controlled Vehicle Speed Idle and AUX input code

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P1502 Throttle Jacking Unit, Spring Test – Above Limit

Fault area

Throttle return time too long. – Throttle part

Is this the unit attached to the pedal?

I should also mention that I just changed the battery on the car. I have read a few other threads where people have had the same issue after a battery swap!

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Um... you didn't say that before.

Disconnect the battery again.

Turn the key to "on" but do not start or touch the gas pedal - wait 1 minute - turn the key to off and remove the key.

Reinsert the key and start the car - see if it revs now.

Sorry should have mentioned that earlier! I tried that already but cycled the gas pedal after the minute....I will try again. I have the throttle body off so I should see the valve move when I depress the pedal correct? Or should I put the TB back on the car?

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The Saga continues....I tried the relearn process again.

With the TB still removed if I cycle the key aprox 10 times I can here the motor on the TB come to life, and it functions properly when I depress the gas pedal. There isn't any consistancy on the number of times I have to cycle the key before the motor engages. The accelerator pedal feels like it is binding a bit when I depress it, but It may have always done this and I didn't notice since I haven't driven this car in 6 months.

Gotta love intermitent snags!

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Problem solved! I cycled the key until I heard the motor on the Throttle body engage, I then left the key on for one minute, then turned the key off and removed from the ignition. The throttle works everytime now!

thanks for all the help Loren!

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