anyone have any thoughts of what else might be the cause? N75?????

 

bump

 

Since your car is revelently old, and you've tried to replace all the possible units...than my guess will be the "ageing of your electronic components".
Due to the fact that any cars electronic components (especially wires) gets deteriorate after a few years of excessive heat and cold, and according to V=IR, with a deteriorate wire ,you will have a bigger resistance, which means low voltage ,low amps. Which your ECU depends on your sensors to calculate and make adjustments to your car, so with the deteriorate components, there is no way your ECU will collect the right info at the precise timing, and the result will lead to mis-spark, mis-calculate air intake, gas guage spray, and turbo...
Also, I would suggest you to check up your battery to see if its too old, so your alternator might work all the time, and cost you more fuel and hps.
And probably, you might have to try some aftermarket products...

 

Between the ects, the 02 sensors and whatever else youve done to the car, you might still be stuck in limp mode from a previous time. If the fault codes werent cleared before, this would be the case. Are you sure the codes were cleared?

 

The only way that I have tried to clear the codes was by using the autozone scanner and also by disconnecting the negative battery terminal for over 20 mins. When I cleared the codes yesterday I did a check first. I didn't get any results back from the diagnostic and both the ECTS and O2 codes were gone. Is the VAG COM the only way to really get the car out of a closed loop state? Also would the VAG COM be able to determine whether the N75 is going bad?

 

Drive at least 40-50 miles for the ecu to completely re-adjust from the reset.

You will either feel things back to normal, or you should start seeing codes again.

 

just got back and 163 miles later it threw a code, got it scanned again and it said the same as before: PO422 main catalyst below threshold. I am going to have to change the foulers around and see if that might work. I am going to check tomorrow and see if the waste gate rod is broke and I did go out today and bought a new N75 valve but haven't put it on yet. For some reason something tells me that I should hold out before I install that. Is there any way to check to see if it is bad. I just found this and the last post is what happend to me while the check engine light was on before I replaced all these parts.. N75 going bad?

 

How to check N75:

[IMG]local://upfiles/10408/595BCA7505E144DB93C3C6E43E8856D7.jpg[/IMG]

 

Ok so today I replaced the N75 and it did nothing. I didn't have enough time to swap around the non fouler setup but I will this weekend when I have more time. I did check the inducer side of the turbo and there were no chips or fins out of place, the turbo didn't move forward or aft nor side to side but just a hair up or down. I mean it barely moved up and down. I also checked the waste gate rod by sliding a coat hanger around and slid it to the back of the turbo to see if it was broke. The rod made a sound like a loose shim would make, you know that "jangle" type sound but it didn't feel like it was broke or off.
Also today I drove by a really enclosed sub division and heard a rattle flapping sound that varied with throttle input. My guess is that it is the waste gate flapper flapping around and that would make sense on my low boost issue and significant power lose. Now I don't know if the actuator is shot too or if I just need to tighten the rod up.
So how do I test if the actuator is bad? My assumption is if the actuator is bad then by unplugging the N75 the car should in theory boost like crazy since the N75 is not regulating it, but if the car acts the same as before then the actuator is bad. Long story short I believe the turbo needs to be pulled.

Also where do I find replacement actuators for sale in case I need one?

 

Good troubleshooting you have been doing. how many miles do you have?