How to check a ECU?

[MarT2]

Hi all!

I finished my ABY to ADU upgrade, and I fit a RS2 ECU.

From 0 to 0'4-0'5 bar all is OK, but when I go more than 0'5 bar, the engine fails and don't run OK.

I tried the engine with vag-com, and all is OK.

I suspect than the problem is the ECU, because if I don't go more than 0'4bar the engine runs very very good!

How can I check if the ECU is bad?

Cheers!

[UrS4boy]

You should suspect a problem with the boost pressure line going into the Manifold Absolute Pressure (MAP) sensor and/or the MAP sensor itself. It sounds like you are only running on the wastegate spring boost.

Check this out, it might help you:
http://forums.audiworld.com/showthread.php?p=18863287

If could also be the Mass Air Flow (MAF) sensor: http://forums.audiworld.com/showthread.php?p=18863095

[MarT2]

No, the fault isn't the MAP sensor because I go with N75 disconnected and there are a big difference.
And can't be the MAF because it's new.

[UrS4boy]

No, the fault isn't the MAP sensor because I go with N75 disconnected and there are a big difference.
And can't be the MAF because it's new.

Well 0.4 to 0.5 bar is about the same as with the N75 disconnected so I don't understand why you would see a big difference.

As for the MAF, if you read to the bottom of the link I gave you, one of the problems with the MAF is the harness connector female pins sometimes get pushed back out of the connector and do not make full contact with the MAF male pins. At least check that before you dismiss the MAF as a potential source of the problem.

[MarT2]

No, the problem is that the car boost more than 1 bar but in 1 second go down to 0'4-0'5 bar and don't run good, it do bad explosions.

I checked the MAF, injectors, N75, no leaks, etc.

Anybody know how can I check if the ECU is OK?

Vag-com doesn't find any fault code!

Sorry for my english and thanks!

[MarT2]

Anybody know how check it?

[S2central.net]

This thread is hard to follow... I cannot post in Spanish - which is part of the problem I think.

Has the RS2 ECU been modified - or is it stock / factory setup ?

The ECU may be perfect, but maybe you have some air leaks causing safety shutdown - have you thoroughly leak tested it ?

Boost leaks only sometimes give fault codes - very annoying I know...

Always worth trying a spare MAF if you can - RESET the ECU first of all though - unplug it for a minute !

[AUDIS2avant]

ive had this problem for a short wile, check the dump valve for leaking, or maybe it´s broken

[chipsenter]

I had the same failure on my s2 when i used bigger maf, injectors, turbo etc.
i the sw is modefied try to get stock inside, and also been mentioned above about the maf. if that is broken the motronic has a limp mode and it can be true that boost is set to 0,4 like ground pressure.

if the maf is broken it will run exactly the same with cable unplugged though.

-if ECU is broken it wont start the car , check mapsensor.
-check boost after u unplugged wg hose be careful !
-check leaks in pressure system.

worth a try .

J

[MarT2]

Hi!

First thanks for your replies!

I bought the ECU throught ebay, I think that it's stock setup, but I don't know.
I checked the MAF in other car, and it's OK!
DV, N75, and leaks tested!
If I unplug N75 I have 0'4 bar.

How can I test the MAP sensor?

Now I will mount my ABY ECU for proves.

Cheers.

[MarT2]

I tryed the car with my stock ABY ECU and the car still runs wrong.
Now we can discard ECU and MAP sensor.

Is possible that the fault is in the timing? I mounted the complete RS2 timing, exhaust cam, cam pulley, cam belt, cam belt tensor and water pump.
I think that I mount the marks correctly.







Thanks

[MarT2]

Is correct the timing?

Is possible that the problem is that the crank bolt is not properly tightened?
I tightened it with a impact gun.

Cheers

[jade]

Is correct the timing?

Is possible that the problem is that the crank bolt is not properly tightened?
I tightened it with a impact gun.

Cheers

You tighten it to 450nm with a crank locking tool & a impact gun ???

[UrS4boy]

Is correct the timing? Is possible that the problem is that the crank bolt is not properly tightened? I tightened it with a impact gun.

It *IS* possible you broke the pulley key with the impact gun. Using an impact gun on these 3B, AAN, ABY and ADU crank bolts is just a real bad idea. See photo.

[S2central.net]

Oh dear - oh dear - how many times do we tell people on this site to be careful with the crank bolt. It is such a critical area - NEVER tighten it with an impact driver - you have absolutely no idea how much torque is being applied to the bolt.

Strip it down again - inspect or replace the crank pulley - and rebuild it properly.