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Discussion Starter · #1 ·
Maybe someone on here knows what the heck is going on with my '99 2.0 AEG VW New Beetle. My car keeps going into some sort of limp mode with a throttle surge at low RPMs after driving for a while. My european import auto shop is out of ideas since it's so inconsistent.

The first time this happened, I drove ~8 miles on the highway to get to work and when I got to work after stopping my car at a stop sign, it went into some sort of limp mode and would not accelerate past 10mph (while foot is on the pedal the car has a rhythmic throttle surge). Turning the car off and back on sometimes fixes the issue and lets me drive for another half mile, mile, several miles (it's random). So far it has only happened at low RPM's when my car has to slow down or be in start and stop conditions. Usually happens after driving for a while.

It has also thrown a P1543 (throttle actuation potentiometer signal too low) code and my throttle body was adjusted and replaced. Replacing the throttle body didn't fix it and the vagcom shows 5 different codes. My shop is out of ideas after checking voltages and things. Attached is the results from the Ross-Tech vagcom scan. I'm not ready to give up on this Beetle. HELP!


 

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Well, all codes shown; are pointing to the throttle body. As for the "limp mode", when a major mechanical failure occurs or the ecu, is NOT receiving a data stream or connection, from a major component (like the throttle body), the car will go into the infamous, "limp mode" to protect the car and ostensibly, safely get you off the road.

As these cars age, we are seeing more/more problems with the throttle body issues and so, you are NOT alone with this problem.

Troubleshooting a throttle body; has been typically broken down into a number of steps or areas to look at.

Throttle body alignment settings/cleaning process:

When a VW has a electrical or charging issue; it can lose, it's throttle body alignment settings. Traditionally, one would recommend; a through cleaning fo the throttle body and do a throttle body alignment procedure with a VW specific scan tool like VCDS by Ross Tech. This requires, a certain amount of conditions be met; for this to be done successfully or you will get a error, the TBA process will fail. More details and conditions needing to be met here: (be sure to watch the video; at the bottom of the page):

Throttle Body Alignment (TBA) - Ross-Tech Wiki)

Sometimes, the throttle body itself and internal electrical sensors are damaged and this requires replacement but in my experience, it is usually electrical in nature. However, I did have a older 1997 Audi A4 1.8T with a cable drive system (not drive by wire); which, ended up being bad and would not go through the alignment procedures, no matter what I did. Replacement of the throttle body with a new one; fix the issue and the car ran correctly, after that.

Intermittent issues, we have been seeing lately; are the failure of the wiring harness to the throttle body, the plug itself being damaged/bad and the termina end contacts, getting loose, over time, intermittently losing connection/data communication with the bus to the ecu. Hooking up the car to a scan tool, that can read live data and doing a output tests, to "see" if the data stream to the ecu is being read and wiggling the wires/harness/plug to the throttle body, would be another technique to diagnose/troubleshoot the problem.

If the live stream data, is seen to "drop out", replacement of the terminal ends and the plug, are the typical fix for that. Beyond that, testing the terminal ends; according to the factory vw service manual testing procedures, would give you a "pass/fail" to the wiring and ecu (correct voltage, ohm readings, etc). No signal, would require, pull the ecu and testing for continuity to the ecu and then, if that was ok, possibly the ecu is bad. Be sure to check the manual; for step by step testing and troubleshooting procedures.

Here is a excellent thread; where a member, FINALLY, fixed his intermittent problem and it turned out to tbe the wiring/harness/terminal ends/plug were compromis, to the throttle body itself. So, in that case; the connection to the throttle body, was not working correctly and the ecu, was not getting the data it needed, thus, a bunch of throttle body, related trouble codes, were thrown.

https://www.newbeetle.org/forums/1-...ed.html#/forumsite/20963/topics/124170?page=1

Hopefully, this gets you started; on how to approach the problem and testing ideas, how to troubleshoot things. Ultimately, a process of elimination; should help you find the issue and fix the car! Let us know, how things process and we can go from there! Thanks! :)

If you have anymore questions or need help! Let us know! Thanks! :)
 

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Discussion Starter · #3 ·
Well, all codes shown; are pointing to the throttle body. As for the "limp mode", when a major failure occurs or the ecu, is NOT receiving a data stream or connection, form a major (like the throttle body), the car will go into the infamous, "limp mode" tor protect the car and ostensibly, safely get you off the road.

As these cars aga, we are seeing more/more problems with the throttle body and so, you are NOT alone with this issue.

Troubleshooting a throttle body; has been typically broken down into a number of steps or areas to look at.

Throttle body alignment settings/cleaning process:

When a VW has a electrical or charging issue; it can lose, it's throttle body alignment settings. Traditionally, one would recommend; a through cleaning fo the throttle body and do a throttle body alignment procedure with a VW specific scan tool like VCDS.

Sometimes, the throttle body itself and internal electrical sensors are damaged and this requires replacement but in my experience, it is usually electrical in nature but I did have a older 1997 Audi A4 1.8T with a cable drive system; ended up being bad and would not go through the alignment procedures, no matter what I did. Replacement, fix the issue and the car ran correctly, after that.

Intermittent issues, have been seen lately; as failure of the wiring harness to the throttle body, the plug itself and the termina end contacts, getting lose, over time, intermittently losing connection/data comms with the bus to the ecu. Hooking up the car to a scan tool, that can read live data and doing output tests, to "see" if the data stream to the ecu is being read and wiggling the wires/harness/plug to the throttle body, would be another technique to diagnose/troubleshoot the problem.

If data is seen to "drop out", replacement of the terminal ends and the plug, are the typical fix for that. Beyond that, testing the terminal ends; according to the factory vw service manual testing procedures, would give you a "pass/fail" to the wiring and ecu. No signal, would require, pull the ecu and testing for continuity to the ecu and then, if that was ok, possibly the ecu is bad.

Here is a excellent thread; where a member, FINALLY, fixed his intermittent problem and it turned out to tbe the wiring/harness/terminal ends/plug to the throttle body.

https://www.newbeetle.org/forums/1-...ed.html#/forumsite/20963/topics/124170?page=1

Hopefully, this gets you started; on how to approach the problem and testing ideas, how to trouble shoot things. Ultimately, a process of elimination; should help you find the issue and fix the car! :)

If you have anymore questions or need help! Let us know! Thanks! :)
Thanks for your thorough response. I will talk to my mechanic about this
 

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Well, I and many others, have worked on similar issues. So, you are NOT ALONE! :) I do think, the thread I posted about; is probably, the best one, we have seen so far about troubleshooting the issue. Loose terminal ends and bad/damaged plugs to the throttle body; should not be overlooked and could be the cause, of many people's problems, aside from a damaged/malfunctioning throttle body itself. Good luck and I hope you get it fixed soon! :).
 
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