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Discussion Starter #1
Hello Everyone,
i have been trying to diagnose my engine's problem for some time.

The car is going into the limp mode under high load, after 2000 rpms and climbing uphill.
I have been trying to follow the procedures i have found in the DIY section but still could not solve the issue.

I believe the car is having problem with the air intake quantity.

I would like to briefly explain what i did so far.
- the turbo is stock. the car has Rocketchip stg 3 chip on it with pp520 injection nozzles. it also has a BoostValve to prevent overboost. it also has EGR valve delete.

- i tested the N75 and it seems to be really ok. during the test it clicked and has a good resistance of 16 ohms.

- when i diagnosed with VAGCOM, i noticed that the Manifold pressure (measure group 11) is almost always about 100 mg units lower than the Requested amount.
at idle, the requested is 1100 mg, vs the actual being 1020mg.

i have tried to see if the turbo vents are stuck, i freed the actuator rod and tried to open and close the small lever by hand. it moves freely.
i also saw that the actuator moving the vent lever about 1cm down when my friend started the car.

- Mass air flow sensor is new. the mesausre group 3 reveals that the expected is fixed at 850. at idle, the actual value from the Mass.air.sensor is 530-540. while driving it can go up to about 800 or 820 at high loads usually just before the car goes into limp mode..
when i was replacing the mass air sensor, i did not connect the hose to the airbox to see if a direct flow of air did make any difference for about 30 seconds in the garage. the value stayed at 530-540 and did not make any difference.
when i disconnect the mass air sensor, it jumps up to 1250. does not prevent the car from going into limp mode in high loads.

my questions
1. i find it strange for the expected value from Mass airflow sensor to be fixed at 850 all the times. also, unplugging the sensor does not make any difference either.
what could be causing this requested fixed value?

2. The manifold pressure is always in a ratio with the requested pressure. i mean when the requested is 1500, the actual is about 1300-1350 etc. seems to be always a percentage of the requested pressure.
could intercooler be clogged? if so, how can i clean it?

what would be the first place you would look next?

thank you so mch in advance.
 

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One thing about tuned cars is that sometimes the sensor readings can be off. I'm not 100% sure of this but I think some tunes will show a strange MAF reading due to how they work. Ask rocketchip directly if their tune will change any of this before digger deeper. I think the MAF is one of them.
 

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Discussion Starter #3
thanks for the idea. i will definitely call them and ask about this.

about the MAF sensor reading range, is the range of 530(idle) - 820 (under heavy load) normal for a 01 Golf TDI?
 

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530 is high. 820-850 is correct. There should be a label "tool tip" that shows up around the measuring blocks in VCDS. Not the newest models but for the 2001 they're all out.
 
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