HELP! Mechanical boost only - mostly!?

[newsh]

On the bulkhead near the ISV, all the engine electronics go through these 2 big round plugs, Also all the grounds for the engine sensors go to the bolts on the underside of the Inlet Manifold down below the FPR.. Any problems with either of these and you'll get all kind of random faults being thrown up.

[madpugger]

It seems like I had totally forgotton I own this car! I have had no time to look at it, but am thinking I am going to have to as I want to sell it at some point, I'd hate to have to break it!

Does anyone have a VEMS map for a 3071 with RS2 injectors? I have a vems here i could try in the car to eliminate some stuff before I send the ECU to the place what chipped it...

[madpugger]

Oh, I forgot...

I noticed that it gets boost much more often when cold, but still only to around 4k. When hot its only occasionally gets boost until 4k... Mechanical only after that.

[prj]

Did you pressure test it?

I read your thread again, and I think there might be a leak in the connection between the ECU's MAP sensor and the intake manifold.

You will know if you do a leak test.

[madpugger]

I have not yet, but will have a look, although the boost gauge works and is off the same line.

Also, it is throwing check sum codes...

[UrS4boy]

Did you pressure test it? I read your thread again, and I think there might be a leak in the connection between the ECU's MAP sensor and the intake manifold. You will know if you do a leak test.

Sorry I didn't get into this thread before because the first thing I would have said is:

"Check your moisture trap connections" (this is a well known UrS4 problem and results in the ECU not getting any boost feedback, hence only mechanical boost)

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

[madpugger]

Sorry I didn't get into this thread before because the first thing I would have said is:

"Check your moisture trap connections" (this is a well known UrS4 problem and results in the ECU not getting any boost feedback, hence only mechanical boost)

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

I will give it a go, but still, it pulls check sum error codes... with the fuel map in two ECUs...

[prj]

"Boost gauge works" is not a substitute for a leak test
If the chip throws codes in both ECU's, the chip is bad.

[madpugger]

"Boost gauge works" is not a substitute for a leak test
If the chip throws codes in both ECU's, the chip is bad.

Which is why I want to try a vems map, make sure its not something AS WELL AS the ECU that I can be fixing while the ECU is down south

Also, I am sick to death driving a diesel 306 thats quicker than the supposed to be ~430 BHP S2

[prj]

I can't really believe that you would fit an aftermarket ECU over something as simple as a leak test, especially since boost leaks probably account for like 90% of all issues in turbo engines.
Check your cambelt, are you sure it's not slipped one tooth? That will also cause mechanical boost.
Also try a different MAF.

The things causing the boost control to not work from your error log are G40 and G71 errors.
The rest do not affect boost.

And the G40 error can be caused by the cambelt being 1 tooth wrong! BTDT. I was ready to tear out my hair when after weeks of troubleshooting, measuring n75, trying three different ECU's and swapping half the senors around we found out the timing marks didn't line up.

[prj]

P.S.
The original ECU's don't go bad often.
You should closely inspect the soldering on the MAP sensor though...

Btw, with VEMS you will 100% have boost, because VEMS won't turn your boost off pretty much no matter what, as it assumes you know what you are doing. Unlike motronic, which assumes that you don't and tries to interfere in all ways possible to save the engine.

[ericd]

I will give it a go, but still, it pulls check sum error codes... with the fuel map in two ECUs...

sorry if I'm stating the obvious , but the checksum error exists because somebody has modified the code and either not tidied up behind, or didn't realise that they had to, anybody that lives/works in the land of binary will have seen similar on various ecus from various cars , some people do it specifically so you can see it's been modified , Nothelle is a prime example, it can be fixed so it don't show up , paul, mihnea, doug and a good few others could get rid of the checksum error, it's a red herring though as the source of your running problems IMHO

hth

[madpugger]

I am not saying i wont do a boost leak, I am saying that the ECU will be back with the tuners for a month more than likely, and I would like to be able to at least move the car!

It had a new MAP sensor and sockets fitted by the tuner, and the boost map is obviously faulty, so that is for them to fix, i am not touching it!

[ericd]

can you get to the meeting (Famous Grouse) at the end of the month with the car

[prj]

I am not saying i wont do a boost leak, I am saying that the ECU will be back with the tuners for a month more than likely, and I would like to be able to at least move the car!

It had a new MAP sensor and sockets fitted by the tuner, and the boost map is obviously faulty, so that is for them to fix, i am not touching it!

It's not faulty.
Just the checksum doesn't match, it doesn't mean it's faulty.
It's possible it has been there all along.

The checksum in the boost chip is a bit harder to correct than the fuel chip, but if it's MRC they know how to do it
Also, a bad checksum will have absolutely zero effect on your car besides throwing that fault. Zero, zilch, nada.

It's the G40 and G71 errors that you have to get rid of for it to boost again! Those can't be caused by bad mapping either.
Maybe badly soldered MAP sensor or a leak, or bad contact to the sensor.