as above guys its driving me mad i have no fault codes changed fuel filter crank sensor and no joy car starts to boost then its like limp mode my last thing i can think of before breaking it is maybe my m8 put the fuel lines by the bulk head the wrong way round hence it looks right from the fuel filter end would this cause this?

Run any logs on VCDS?

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Is the turbo and injectors set up correctly?

...last thing i can think of before breaking it...

 

Sounds like it's already broken to me.  :p

 

You say it starts boosting but what exactly does it do, does it start misfiring, does it stall, is it like hitting a rev limiter?

 

What do you mean the pipes at the bulkhead might be the wrong way round? One pipe is fuel supply, the other is fuel return, it's child's play to test by removing each pipe from the filter and seeing which one fuel spews out of when you turn the key.

If the fuel pipes are the wrong way around surly the symptoms would be no starty? :P

Said it before and I'll say it again.

GROUP 11 LOG!

As its going into limp mode theirs a good chance this is due to overboost. So a group 11 log in 4th foot down from 2000 rpm up to the point it goes into limp. Then look at the data or post it. This will show if it's over boosting and causing limp. If it's not then it one thing you can rule out.

Said it before and I'll say it again.

GROUP 11 LOG!

As its going into limp mode theirs a good chance this is due to overboost. So a group 11 log in 4th foot down from 2000 rpm up to the point it goes into limp. Then look at the data or post it. This will show if it's over boosting and causing limp. If it's not then it one thing you can rule out.

 

Just read my mind

 

It's not that it won't rev past XXXX - It's that the car is shutting down due to some setting / sensor being surpassed and it killing the system to preserve it.  You may be thankful for that in the long term, however much of a pain in the backside limp home mode is.

Yeah Steves back with the same old stupid threads!

Just what I needed on a cold frosty morning a good laugh

Said it before and I'll say it again.

GROUP 11 LOG!

As its going into limp mode theirs a good chance this is due to overboost. So a group 11 log in 4th foot down from 2000 rpm up to the point it goes into limp. Then look at the data or post it. This will show if it's over boosting and causing limp. If it's not then it one thing you can rule out.

Head+wall+bang them together

Said it before and I'll say it again.

 

"Dance while the record spins....."

 

Anyway this disproves our theory that SteveOPC was the guy who got sent down for doing 180+ MPH on the road and videoing it...

Thanks Steve for sending the log. I've put it into a graph and added it here in the aim to help others who may suffer the same issue and come searching the forum for help.

 

Blue line is the request boost from the ECU.

Red line is the actual boost recorded by the MAP sensor.

Green line is the duty cycle. So the N75 percentage which means what the ECU is requesting in term of the vane position. 0% being fully closed to increase back pressure and increase boost, 100% being fully open so as little back pressure as possible.

 

Looking at the log we can see the boost start to build up to 2500 rpm then the begins to drop. To try and counter act this the ECU closes the vanes to try and increase pressure but it doesn't work.

 

Question. Has it ever worked since the head was rebuilt and put back together?

 

1. If the answer is no then I would check all the vacuum pipes have been fitted properly and correctly. If so go to step 2.
2. I would then recommend you connect a vacuum tester to the actuator and check to see it moves under vacuum without any restriction. If it does then at what pressure does it hit the stop screw? Stock GT17 turbo's should hit the stop screw at around 17.5-18 on the gauge. If so go to step 3.
3. Disconnect the actuator arm from the VNT leaver and check the VNT moves freely. This is just another double check of the above. If so go to step 4
4. I would then look at the vacuum box and anything else which is part of the vacuum system.

 

I'm no mechanic so the above is probably **** lol

 

 

 

thanks john you have a pm

Is it me or is the duty cycle crazy low suggesting the actuator arm is way too long?

Is it me or is the duty cycle crazy low suggesting the actuator arm is way too long?

my m8 messed about with the actuator tbh trying to get some boost just haven't been put back in place

Edited 10 December, 201510 yr by steveopc

Did he mess about by making it longer not shorter?  Whadda mistaker de maker (Allo Allo reference)

Get. Vacuum tester on it and make sure it's set correctly. I think the problems elsewhere as I've not seen an actuator set too long stopping it from driving up the Rev range.

my m8 messed about with the actuator tbh trying to get some boost just haven't been put back in place

Surely put that back to where it was when it was mapped before you start threads asking for help or doing any logging?

That is some good service you've offered there John!

Get. Vacuum tester on it and make sure it's set correctly. I think the problems elsewhere as I've not seen an actuator set too long stopping it from driving up the Rev range.

 

Is it possible the underboosting is putting in to limp mode so it's just stopping @ 3,200?  I know in limp mode my car barely gets above 3200.

That is some good service you've offered there John!

Highly commendable

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Steve, why the hell did you let your mate adjust the thing when it was working fine!?!! 

Steve, why the hell did you let your mate adjust the thing when it was working fine!?!! 

head gasket gave up twice in 3 weeks I sent a spare head away for work bought a new cam from nps had new valves and stems seals fitted then engine removed bays painted white and we built engine up around a good spare block I had along with a head stud kit, we adjusted the actuator a little before fitting engine back in to get the boost in a little earlier but I then had to pop out for an hr or so and left him to it and I suspect he played with it without me knowing he also cross threaded the bolt holding the heater matrix pipes to heater matrix in bulk head leaving me no choice to remove dash (yesterday) and change that aswell lets just say he won't be working on it again

Hi Steve

Thanks for the stop screw log.

Actuator On = 973.3 mbar

Actuator Off = 973.4 mbar.

So no difference in pressure. Should be around 90mbar different for a gtb.

This tells me the actuator isn't moving so staying in the fully open position so turbo is unable to create boost.

Do the test again but this time get underneath and look to see if the actuator is moving. My guess is it doesn't move.

If it doesn't move then this is your problem which needs sorting.

When you get the vacuum tester. Hook it up to see if the actuator moves under vacuum. If not actuator is the root cause. If it does move then you've got a vacuum problem.

Edited 16 December, 201510 yr by faboka vrs

Good bit of diagnostic work there, sounds like an easy fix really

IIRC from another thread you took off all the vacuum pipes then couldn't remember where they went?

As suggested on that thread a good few months ago double check your pipes are correct........