Audi S3 boost problem

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FinAudis3

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Hello! Im having major lack of boost in my audi s3. Car also runs badly on cold starts and the exhaust pops when shifting gears.

i have changed the following:

MAF
N75
Turbo boost sensor
Coils
Spark plugs


And still the same problem, i also tried unplugging the hose from n75 to the wastegate which resulted in good boost so no leaks? Please help
 
FinAudis3 said:
i also tried unplugging the hose from n75 to the wastegate which resulted in good boost so no leaks? Please help
Click to expand...

Wastegate actuator on the turbo has failed or is failing by the sounds of it.
 
Thanks for your response! Im new to the tuning scene and all soo do i need to just order a new actuator? Because doesnt the ko4 have a internal wastegate? Im asking this because if the wastegate is internal so is the actuator which means i have to take the whole turbo out for the actuator replasing. This would be a perfect time to upgrade the turbo to a better one, is there any other bolt on turbos expect the stock ko4? And im running Apy -99
 
Fault codes which came up was
P0238 turbo charger boost sensor ”A” circuit high
P0102 Mass or volume air flow circuit low input

I changes the maf and the turbo boost sensor and the codes didnt clear. I checked the cables with a tool and the cables are not faulty there is power in the cables. Im gonna buy a vagcom cable tomorrow and read them again with it. Thanks for the attention!
 
http://wiki.ross-tech.com/wiki/index.php/16622/P0238/000568

Suggests a faulty MAP sensor... make sure you only use a genuine Bosch sensor as a replacement...

http://wiki.ross-tech.com/wiki/index.php/16486/P0102/000258

Suggests a fault MAF sensor... again make sure you only use genuine Bosch parts...

This will be contributing to your lack of boost as these are key sensors the ECU needs to calculate airflow and read pressure in the system... without them the ECU will not allow boost to be made beyond actuator pressure

<tuffty/>
 
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<tuffty/> said:
http://wiki.ross-tech.com/wiki/index.php/16622/P0238/000568

Suggests a faulty MAP sensor... make sure you only use a genuine Bosch sensor as a replacement...

http://wiki.ross-tech.com/wiki/index.php/16486/P0102/000258

Suggests a fault MAF sensor... again make sure you only use genuine Bosch parts...

This will be contributing to your lack of boost as these are key sensors the ECU needs to calculate airflow and read pressure in the system... without them the ECU will not allow boost to be made beyond actuator pressure

<tuffty/>
Click to expand...
Hey tufty, i checked the fault codes with vcds and it shows me the map sensor. I have replaced the map sensor month ago. tried clearing the code without car running and it came back instantly. Checked the wiring and there are 3 pins in which 2 are 5 volts. What is going on? The map sensor is new and the wiring seems to work. Please help. Oh and edit all the sensors i have replaced are genuine bosch
 
Last edited:
And i was measuring blocks during WOT this is what the vcds was showing:

Engine speed 6440/min
Engine load 124.7%
Boost pressure (specified) 1730.0 mbar
Boost pressure (actual) 2540.0
And this whole time during the acceleration turbo boost was 0.2-0.3 bar

and the car had been mapped but when the problems started we mapped the oem map back to the ECU.
 
audi upgrades
Ok so you didn't mention you had flashed it back to 'stock'... was it the original file you took from the ECU?

<tuffty/>
 
<tuffty/> said:
Ok so you didn't mention you had flashed it back to 'stock'... was it the original file you took from the ECU?

<tuffty/>
Click to expand...
Yeah sorry about that im new in the forum, but yes when i mapped it we saved the original map and mapped it back to the stock few weeks ago.
 
does flashing the 'mapped' file back in cure the issue? just seems a bit coincidental that its happened since the flash...

<tuffty/>
 
audi upgrades
<tuffty/> said:
does flashing the 'mapped' file back in cure the issue? just seems a bit coincidental that its happened since the flash...

<tuffty/>
Click to expand...
Will try that next week. Tuffty does the boost pressure specified and actual look wrong in
Your opinion? Thanks for the answers!
 
FinAudis3 said:
Will try that next week. Tuffty does the boost pressure specified and actual look wrong in
Your opinion? Thanks for the answers!
Click to expand...

Boost pressure (specified) 1730.0 mbar
Boost pressure (actual) 2540.0

Assuming this is correct... the ECU is asking for 0.7bar and is seeing 1.5bar... that suggests its over boosting... you ideally need to log a run to see what actual is at any given rpm under load and see if the MAP sensor is actually working... also need to log airflow... and N75 duty

<tuffty/>
 
But how is it possible that the ECU is seeing 1.5 bar if the boost gauge is showing 0.2 bar during the whole WOT from 2k rpm to 7k rpm? It seems like my ECU is drunk. And if the ecu is requesting 0.7 bar that seems like the stock map because stock boost is 0.7. It seems like my MAP sensor is working but its sending crazy numbers to the ECU, in no way there was 1.5 bar in the system because my boost gauge and me myself was feeling the lack of boost which was the 0.2 bar. Thanks again for the response Tuffty! EDIT: And i checked the MAF airflow it seemed ok. I need to check the N75 duty cycle. Can you tell me what block is it and whats the normal numbers when checking the duty cycle?
 
If you trust the boost gauge then it suggests the MAP sensor is the problem

<tuffty/>
 
put simply.... the ECU can only work off info from its sensors... if the information the sensors relay back to the ECU is incorrect then it won't know unless its outside of normal operating parameters..

The map is the map... the code doesn't change in this context as the map sensor data is hard coded in this particular ECU...

Whats the part number on the MAP sensor?

<tuffty/>
 
Tufty the pull i did was on 3rd gear WOT and those were the values i mentioned earlier. Also i dont know what the serial number of the map sensor is but i know its genuine bosch.
 
yeah but ideally need to seem them in context of the log...

As for the MAP sensor, being genuine Bosch is fine as long as its the correct part... there are many different types that will 'fit' the S3 but they are rated to different pressures.... the OE S3 MAP sensor is rated to 2.5 bar (1.5bar with typical atmospheric pressure)... I have used MAP sensors rated at 4bar and 3bar on standalone ECU's and all need to be calibrated... the ECU is calibrated for a 2.5bar sensor so if the sensor you have is incorrect then it could be outputting a signal that the ECU is interpreting incorrectly...

Without seeing a log of the run its difficult to comment... I have written up a piece on logging and how to post in the FAQ's...

Basically the ECU think s its seeing 1.5bar of boost pressure and its only source for this information is the MAP sensor... so thats either faulty, not the correct part or there is a wiring issue where the signal the ecu is seeing is 5v or something...

This is assuming that its not actually seeing 1.5bar of course

<tuffty/>
 
Hey Tuffty, im trying to find the FAQ logging thread but cant find it, can you link it?
 
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