Mk4 GTI Throttle body doesn't know what it's doing

[Malk234]

Having the same problems over and over.

Throttle body can't be reset on ross tech/vagcom, it comes up with an error at about 30-40 degrees.
When driving, engine almost stalls coming off boost after pegging it or it jolts backwards and forwards on %5 - %10 throttle 80 percent of the time.
Replaced ignition barrel and that somehow gave me more torque and consistent boost but didn't help. Checked the wires from the ecu to the throttle body positioning sensor and they all have continuity. Nothing else comes up when it scans other than to reset the throttle body/reset manifold. Had Volkwerke try to reset the throttle body but to no success. Used a brand new throttle body from them too and it did the same thing at the same degrees.

If it isn't the wires, what else could cause the throttle body to not get signal to the ecu? Could the ecu be the problem?
Checked the spark plugs and they're all sweet and I'd imagine it wouldn't be coil packs. No dash lights have lit up ever since owning it (it's had this problem since i bought it).

Could it be VVT out of whack? but then that still doesn't explain the throttle body not working.
I'm running out of ideas if anyone has any insight/knowledge to the AGU/1.8T drive-by-cable engines.
I've scoured the internet for the year that I've owned this car and tried everything but still to no success.

Thanks
Todd

[Malk234]

Also I've replaced the pcv valve and that other one way valve that the pcv connects to.

[h100vw]

Also I've replaced the pcv valve and that other one way valve that the pcv connects to.

There's no VVT on an AGU.

The TB will align itself if you turn the ignition on and don't start the engine.

If you have buzzed the wires, did you manipulate the harness at the same time to see if there's a break somewhere that only shows up with movement. Also, did you check to see if any of the wires are shorted to each other? This wouldn't be apparent just buzzing end to end. Had plenty of aircraft faults like that.

Could be time for an ECU though. I have run 018AQ ECUs from A3s on Golfs, so for troubleshooting purposes that might be an option?

If that doesn't work, then I'd look for an engine harness to drop over the engine.

Gavin

[grtuned]

Not sure but is the throttle still controlled by a cable from the accelerator pedal?If it does the adaption channel 60 will not work try adaption channel 98.

[h100vw]

Not sure but is the throttle still controlled by a cable from the accelerator pedal?If it does the adaption channel 60 will not work try adaption channel 98.

All MK4 GTIs in Australia are not drive by wire. He said it fails part way through which makes me think they have the right channel.

Gavin

[Jmac]

My take as ive seen this . Is the throttle being aligned with the cable still attached to the throttle body, its really meant to be set with the cable off, just incase anyone has has been monkeying around with the cable to left revs etc, no resistance ie no cable on the throttle body to align. When it tries to reset it with a cable on it can big time upset it. Happy to hear disagreements with that one. Not saying its the fix but worth a try
Cheers
Jmac

[tmh983]

can you get your hands on an osilloscope? I would trace the 2 seperate throttle position signals coming back from the unit. do this as it runs through the adaption and see if the signals to the ecu are healthy, if they are, then you would suspect the ecu itself is at fault.

[Snail Style]

What Jmac said is also sound advice, have seen that cause issues on other cars too with similar setups.

[Malk234]

Thanks for the good response guys.
Going to try to adapt it again tomorrow without the cable on it.

After taking the battery off for a while and putting brake lights on to drain the power and reconnecting everything, it seems to not do it for about the first 2-3 accelerator let-offs, but then continues.

Could it possibly be the crank sensor? Symptoms sound the same (dies first two cranks and third it runs), revs high at idle and while rolling while gear not engaged, it sits at about 1900rpm until I stop rolling, in which it dies down to 1100-1000.
Still doesn't explain why the throttle body cant adapt though.

If anyone is nice enough around the Eltham/ North-East Melbourne area and wants to check it out to run some tests and attempt to fix it, that would be awesome High chance you'd know my dad too (Bill malkoutzis) so you can have a chat with him too haha

Would really love to fix it before I sell it! I don't want to pass this problem onto anyone else.

[Jmac]

One more to add mate and might be very significant going on your latest info. Disconnect your power steering switch. It might be sending a full lock signal to the ecu and the throttle wont adapt. This is also the case of the idle staying high, ECU thinks your steering is full lock and lifts the idle, make sense??
See how you go, disconnect it anyway and leave it off, more trouble than its worth, me Id delete it as they leak anyway.
Jmac

[Malk234]

Disconnected the power steering switch and it now doesn't die down to 500rpm after I floor it! Still has the %5 throttle jumpy-ness which occasionally comes into play when letting off accelerator; but I am hoping it will now adapt properly.
If it doesn't, any other ideas as to what sensors or anything else that could be buggered, stopping the throttle body from adapting? Only ever goes jolty at %5 throttle. Never any other amount of throttle.

It idles at a consistant (compared to when it fluctuated) 1850rpm while moving though and at 950rpm (much better idle, also not fluctuating) when not moving.
I'm guessing every sensor on this engine is buggered or something? haha

[Malk234]

IAT sensor maybe?

[Jmac]

Na mate it will still adapt even if the IAT is disconnected. Have you tried the throttle yet?? good to hear the power steer switch helped, more trouble than they are worth
Cheers
Jmac

[tmh983]

coolant sensor? new one did wonders for my car...

[leighaus]

Disconnected the power steering switch and it now doesn't die down to 500rpm after I floor it! Still has the %5 throttle jumpy-ness which occasionally comes into play when letting off accelerator; but I am hoping it will now adapt properly.
If it doesn't, any other ideas as to what sensors or anything else that could be buggered, stopping the throttle body from adapting? Only ever goes jolty at %5 throttle. Never any other amount of throttle.

It idles at a consistant (compared to when it fluctuated) 1850rpm while moving though and at 950rpm (much better idle, also not fluctuating) when not moving.
I'm guessing every sensor on this engine is buggered or something? haha

Cool, i get the same symptoms occasionally. Ill do this as well. Cheers JMAC !