3B overboost mistery

[UrS4boy]

Moisture Trap and Manifold Absolute Pressure MAP info

I think that found the problem... not 100% but 95%. the MAP sensor in ECU have damage, because I put my boost gauge in that car ,and shoes the same pressure on idle like my car. -0.8 (0.2bar on dash.) that means the engine have NO LEAK, and ECU have wrong info about boost , and give wrong fuel and overboost... exacly everithing is wrong...good thing is that we will do AAN conversation on that car , and we allredy have AAN ecu. but first they must work fantastic on 3B ECU.

One of the problems with the AAN and low boost is the moisture trap (on the firewall on a C4 S4 and down by the ECU on a C4 S6). The clamps come loose on the moisture trap and the ECU fails to get the proper boost (or vacuum) pressure. I would put money on this being your problem over a bad MAP sensor.

Moisture Trap info:

http://forums.quattroworld.com/s4s6/msgs/20401.phtml

MAP sensor info:

http://forums.quattroworld.com/s4s6/msgs/20417.phtml

[prj]

Indeed, I am 99.9% sure the MAP sensor does not have damage.
It is a very simple device.

Also, did you check the car with VAG-COM?

[mouse]

Blocked cats?

Edit: obviously not now that I've read the thread properly..

[rs200]

people the map sensor are demage 99% because when you give them contact they shoes 1.9 bar than start the car and then shoes 0.7 or 0.8 at idle.
and then I put the external boost gauge it shoes 0.2 at idle and that is ok .

I try to drive the car withot exhaust ,only the downpipe was on the car. it is not problem in exhaust.. car nont have cats ,they are full open..


Moisture Trap are ok, I even check them.

yesteray I swap pipe from wasegate to turbo , to elemenate N75 , and they shoes 1.2 bar on dash , but I was not even start to drive the car in first gear, in that case maximum boost can be 1.5 bar . but not 1.2 in first gear, MAP sensorare are definetly bad ... and this ECU which are on was been opened, I dont know why, maybe someone broke something in them.. we will see..

thanks everyboedy for help, if somethin drop on your mind, please write, thanks.

[prj]

I still don't think the sensor is bad, unless someone opened it and physically tampered with it.

Where do you take the vaccuum for the boost gauge from?
Put a T piece at the ECU and take the signal from there, so you have the same line going to the MAP sensor and also to the boost gauge.

Open the ECU and inspect the sensor visually and the soldering. There also might be cold joint somewhere totally else in the ECU.
It's almost impossible for a MAP sensor to fail by itself in normal conditions.

Measure the MAP sensor's Vref voltage, it should be 5 volts (measure voltage between pin 1 and pin 3 with the ignition ON http://gm.mainframe.no/stuff/freescale.pdf).

[rs200]

well Dmitry the map sensor are bad. now I go to pick up other 3B ECU 150 km away, came home and put it in car..

ignition on 0.9bar (not 1.9).
start the car then drop on 0.3 bar

than amiditly rise the rpm to 3000 and they go to 0.7 -0.8 bar. like it have to be

so the story are over in that part. ecu -map sensor was bad and now we learn that map sensor can caus overboost..

very strange but it hapend. there is no hooker that can give you sex like audi 200 20v can.

[prj]

That does not prove the MAP sensor is bad.
For all you know, there could be a cold joint somewhere in the ECU (a friend had this issue).
Although if it has been opened, it is also possible that someone messed with the sensor.

But it is good that you solved the problem.

[rs200]

yes someone was open the ecu , for no reason, I soo that is scracked backide and backside have 4 bolts and each of it is diferent...

how can I trust this ECU?

[prj]

Open and check.
I told you how to verify the MAP sensor supply voltage...
If that is ok, you can then check the MAP sensor output voltage (Pin 2).
At atmospheric pressure a 250 kpa sensor should read about 1.8V.
And a 200kpa sensor should read about 1.44V.

If the supply voltage is bad for the sensor or it is good and the sensor reads correctly, but output from ECU is wrong, then your problem is somewhere in the ECU.
Otherwise it is the sensor.

Good luck testing.

[rs200]

That does not prove the MAP sensor is bad.
For all you know, there could be a cold joint somewhere in the ECU (a friend had this issue).
Although if it has been opened, it is also possible that someone messed with the sensor.

But it is good that you solved the problem.

sorry for stuppid question but what is "cold joint"? I realy don't know. thanks

[prj]

sorry for stuppid question but what is "cold joint"? I realy don't know. thanks

[rs200]

aha... conection without conection... thanks

[prj]

Also if screws were unscrewed, then 100% someone did something with the MAP sensor.
All 3B ECU's have sockets, so the only reason to remove those screws is to solder/desolder the MAP sensor.

[rs200]

hhahahaaa aaaaaaaaaaaa

new simptoms - new problem...

yesterday when I drive the car it have engine check , blink code test- injector 1 fault code, but injector work fine. I disconected battery over night, and today no more fault code, but ..

start the engine, they work 30 second and day. start again,die again..

i know that someone here have this problem... can somebody help me... please..

[prj]

Are you still using the other ECU?
Get exact codes with vag-com...