Car bogs down, found out throttle capped at 25%

Anyone know what could be causing this? Sometimes when I give the car it�s daily beans, the throttle will become almost unresponsive, plugged in snap on diagnostic tool and found out even if accelerator pedal is pushed to floor, max output is only 25%. When this happens, it will continue until the car is turned off, and interestingly the accelerator will not work while the brake is pressed at all.

Sesrch for the e-gas recalibration priceedure here. Do that first. may not fix it but should be the first step. Kinda sounds like a loose connector.

Here is the deal: One post, new forum member, no background information, no car information, no year or model, not even the most basic of information. How in the world do you expect some help with your problem(s)? We are not wizards...well not most of us.

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Preach it Joe! It should be a requirement to at least have model and type of 996 when starting a new thread. Are we talking C2 or C4... or maybe even a C4S. Are talking Mk1 5-chain engines or Mk2 3-chain engines? Are we talking cable driven throttle or e-gas? We don't know.

Given the dearth of useful information, my WAG is that the car is e-gas and the gas pedal potentiometer (orig. 99660611500 / now 99660611502) is crapping out. *edit* Holy crap, that's a $1,300 part.

Seriously, Joe is right !! But reading my Crystal Ball says the car is an E-gas and with a Snap-On Scanner showing only 25% throttle position at WFO, there would most definitely be some "hard fault codes" stored in the DME... Why didn't you include them in your post ???

Well the car is a 2000 986 boxster S with the motor out of a 996 2001 Carrera. No long term codes, would�ve included them.

So you're saying at full throttle ( pedal) the throttle body only opens 25% and no fault codes? Sounds very implausible because...... Both the pedal assembly and the throttle body have "redundant opposing potentiometers " an A and a B.. A goes from 0v to 5v and B goes from 5v to 0v .. at no throttle, A will be 0v and B will be 5v , at full throttle A will be 5v and B will be 0v ,,,as A rises B falls ... both the pedal and throttle body have this and any deviation from this pattern will cause a fault code and go into "limp mode" ... Check the "actual values" of the pedal assembly and throttle body potentiometers and report back..

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I don�t think its the throttle body that is the limit, I think its some electronics between the accelerator pedal and throttle body that�s telling the TB to max out at 25%. Problem not with throttle body but something else. Regardless, I defer to y�all�s expertise and will find out more from the diagnostic tool. I just ask for your patience as im new to the whole forums thing.

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On cars with E-gas the brake switch (or laying your foot on the brake pedal) will certainly cause this.... If the DME sees two opposing commands ( a STOP command and a GO command) as a safety feature, it will defer to the STOP command and mostly ignore the GO command.. Check your brake switch....... We had this complaint many times on Cayenne with "left foot drivers" ( mostly women) who would try to merge in traffic while having a foot on the brake pedal and one on the gas pedal, and would complain that the car had no power when they wanted it...( the DME couldn't figure out what they really wanted)...a revised DME program with a little "less safety" lessened the complaints...lol

Performed the e-gas recalibration. Found these codes today. Might've been there before, someone else was using the snap on ethos edge tool and they told me no codes, but who knows. P1219 Accelerator Pedal Signal Implausible P1577 Accelerator Pedal Potentiometer 1 Signal Implausible P1578 Accelerator Pedal Potentiometer 2 Signal Implausible Just found this thread, https://www.renntech.org/topic/29701-p1219-p1577-p1578/

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There ya go....that's what we were looking for...... It's showing codes for both potentiometers on the pedal assembly... Check the wiring diagram for wire colors and pin # /location on the DME and test the wires for continuity from the potentiometers to the DME...report back...

Durametric can read the values of each gas pedal potentiometer separately, and I presume PIWIS can do the same. Might also check that. Probably has one failed potentiometer or a bad wire somewhere.