No boost/ limp mode

[M222]

Evening all.
My first post and hopefully someone can help me. I have 2006 d40 that I bought as a non runner after being overheated. I have replaced the cylinder, timing chain etc. Starts and runs on tick over perfect. On the first trip up the road the turbo was sounding like a jet engine. I have fitted a new turbo as the old one was worn out and the turbine was rubbing in the housing. since then it drives better but it is cutting out the turbo when it gets up to 20psi of boost. On start up the turbo actuator arm moves all the way to its maximum travel and stays there. No pulsing on tick over. I have put a tee piece into the vac line that goes to the actuator and connected the old actuator to that so that I can see what is happening from the drivers seat. I have also teed into the pipe that goes to the map sensor and connected a boost gauge to that. When I drive it the boost will get up to 20psi and then the actuator will drop back to its off position with no boost and stay there until I lift my foot of the throttle and put it back down again. I have replaced both the boost control solenoid and the map sensor even though they both tested ok. Replaced all vac pipes and fuel filter. Does anyone have any pointers on what to check next ? Would a faulty scv or pressure relief valve cause this problem? There are no fault codes stored. The only other thing I should mention is there is what I think is an injector rattle when the turbo is working and the engine is pulling. It stopped as soon as the turbo stops boosting.
cheers. Luke

 

[Old.Tony]

It sounds like the ECU is detecting excessive boost and turning it off. It might be worth cleaning the sensor (attached via a small pipe on the vehicle's right hand side to the intercooler piping). We have a similar issue when my Tillix valve allows the boost to go too high (so I turned mine down to prevent that). I don't recall any clatter though.

How long since you've run some injector cleaner through?

 

[M222]

Thanks for the reply. I have a bottle of injector cleaner in the tank now.

I have fitted a new boost sensor but no difference. Also changed the rubber hose to the sensor as that had split. Do you know what causes the turbo actuator to go to its maximum travel on start up with no pulsing ?

 

[Old.Tony]

Only full vacuum will do that, and if you've got a BCS installed, it means it's fully open. While it's unlikely that a brand new unit will fail, it's not unheard of. However, checking the electrical connections (the plug on the BCS, both battery terminals as well) would be my very first thing to do.

If that didn't produce any joy, I'd remove the vac hose from the actuator and start the car, just to make sure it's not something inside the turbo causing the vanes to move (very unlikely, but we're already looking at unlikely problems).

It might also be an idea to check other electrical connections, particularly (and especially) if the engine bay has been pressure washed. In the past, we've seen this cause numerous sporadic and unfathomable problems as the high pressure water forces tiny particles of dirt into the electrical contacts.

 

[OldManBeard]

On start up the turbo actuator arm moves all the way to its maximum travel and stays there. No pulsing on tick over.

Were the vacuum lines disconnected from the control valve by any chance? If so, it reads to me like they may have been reconnected incorrectly.

 

[Old.Tony]

^ I hadn't thought of that, good call.

 

[user 10312]

On the BCV there should be some markings. On one says ATM- atmosphere that goes to the inlet just after the airbox. Vac to the full vacuum line that runs from the other side of the engine and the 3rd one says Acc to the actuator. Well it does on the genuine Nissan jobs.

Sounds like actuator may be getting full vac all the time going into overboost and then ECU going into limp mode.

Just replaced my BCV after it failed. Some say they either work or they don't but I think it has been crook for a while as it's driving nicer now that it has in a long time. Comes on boost sooner and faster and virtually no black smoke.

 

[M222]

Thanks again for the reply’s. I have double checked the vac pipes several times now just to be sure and they all seem ok. Will check the electrical connections. As Tappet has said it is like it is getting maximum boost then the ecu is shutting it down. I take it the turbo shouldn’t go to full boost until the ecu calls for it. Would anything on the fuel pressure side of things effect the turbo ? The only thing I have noticed is there is a green plug disconnected down by the scv. I have looked several times and can’t see anywhere for it to go. As I said in my first post I bought the vehicle as a non runner. Someone before me had either started to remove the scv or has swapped it over. One bolt was out and the other was loose. Thanks again.

 

[M222]

Have had another look at the truck today. Tested the boost sensor and boost control solenoid. Boost sensor tests fine. The only thing that is slightly out is the boost control. Wiring and signal tests both fine but the resistance test comes back at 14.6 ohms when I believe it should be 12.5 ohms. That is on the brand new solenoid. The old solenoid tests at 11.4 ohms. Would this difference in resistance be enough to cause the solenoid to be open to its maximum all the time ?

 

[Old.Tony]

I have never tested mine, so I can't say. I got sick of it failing and went the Tillix valve way.

 

[redkite]

Solenoid resistance between 10 and 20 ohms is probably all good. If the manufacturer of the solenoid bought a spool of wire from a different brand the resistance can easily change a few ohms, while the solenoid is still the same quality.

If a good one measures 12.5, and yours maesures 14, i wouldn't worry about the coil in the solenoid.

However, it can still be mechanically broken. Does it switch when you apply 12V?

 

[Connaught]

Thanks again for the reply’s. I have double checked the vac pipes several times now just to be sure and they all seem ok. Will check the electrical connections. As Tappet has said it is like it is getting maximum boost then the ecu is shutting it down. I take it the turbo shouldn’t go to full boost until the ecu calls for it. Would anything on the fuel pressure side of things effect the turbo ? The only thing I have noticed is there is a green plug disconnected down by the scv. I have looked several times and can’t see anywhere for it to go. As I said in my first post I bought the vehicle as a non runner. Someone before me had either started to remove the scv or has swapped it over. One bolt was out and the other was loose. Thanks again.

I think the green plug down on the right hand side of the engine, near scv is for the solenoid for vacuum controlled cruise control, but dont quote me, been a while since i looked it up,

my car had the same unused plug and i only found reference to that when looking through the manuals for vacuum lines, there would also be a vacuum line from that solenoid the green plug plugs into then to a vacuum port on the throttle body i have been led to believe the cruise control in later models is electronic

 

[M222]

Hi All.
I think I have finally got to the bottom of my problem. After testing the boost solenoid again and the wiring to it I decided the new solenoid must be faulty. Took the old one to bits and cleaned it. Have refitted it and now it’s driving fine. Still no pulsing on the turbo actuator on Rickover but as soon as you put a few revs on the actuator moves up and down. On test drive the actuator moves all the time and no cutting out on overboost. So the moral of this story is just Brouse it’s new doesn’t mean it’s not faulty !!!! Have a light ticking noise now to sort out. Possibly an injector I think. Fairly sure it’s not a mechanical noise.
Thanks again for all your help and reply’s.
cheers