I've been lurking occasionally for quite a while, but I'm getting so fed up with the overboost issue on my 'Troll that I thought I'd see if any of you guys have a clue what's going on with my motor. I know there are lots of threads on here about overboosting and turbo problems and I've read most of them already.
The motor:
A (late) 2005 Nissan Patrol 3.0D GR (what you call a GU, I think) with a ZD30 engine. It is completely standard - no mods of any kind. It has done 50,000 miles (80,000Km) from new. It starts first time, performance is fine, it uses about as much fuel as Patrol's usually do. It doesn't make smoke or use more than a tiny amount of oil between services.
The problem:
Occasionally & usually up hill under load at 2500-2800rpm there is a sudden power loss. Pressing the loud pedal slowly to the floor achieves nothing. Lifting off restores performance. The ECM stores a 0905 error code (boost pressure)
What have I done so far:
1) Replaced MAF sensor (cheapie off Ebay). Tested new sensor with DMM and measured output volts against engine speeds. It's exactly as it should be (per workshop manual)
2) Replace MAP (boost) sensor. Done by Westway Nissan in Oldham. God those are expensive from Nissan!!! This seemed to cure the problem for about 8 or 9000 miles and nearly 12 months. Just before Xmas 2010, the problem returned.
3) Westway Nissan replaced the MAP sensor under warranty, as it seemed the most likely culprit. It didn't cure the problem. I still have the overboost error.
4) Today, I removed the vac hose from the VNT boost control solenoid, put it in my mouth and sucked hard. The turbo VNT rod moved smoothly to the full extent of its travel. I put my tongue on the end of the hose - and the VNT rod stayed exactly where it was. I gradually released the vacuum and the VNT level smoothly returned to its rest position.
5) I've bought a boost pressure gauge (electronic stepper motor type) but haven't yet fitted it.
What do I *think* I know:
* The MAF sensor is probably OK - I'll test it in the morning again to be sure
* The MAP (boost) sensor is *probably* OK - though I'll test that in the morning too.
* The turbo itself is probably fine - at least the vanes aren't stuck or sticky.
* The VNT actuator works and its diaphragm doesn't leak.
* The vacuum hose to the VNT actuator doesn't leak.
* I don't know how to test the VNT vac control solenoid. Any thoughts?
I know that some of the folks on the forum have cured boost problems by fitting a Dawes valve (whatever one of those is), but this motor has worked fine for over 40,000 miles from new and I'm determined that it's going to work fine again, without making any mods.
One possible option is to give the 'Troll to Westway Nissan in Oldham - and tell them to give it back to me only when they've fixed it. I'm more than a bit nervous of that - the last time they had their hands on it, they tried to clear the ECM error codes with a Consult III & didn't understand why that didn't work. I can just imagine them replacing bits at random until it stops generating the overboost error. No thanks .........
Am I missing something obvious here? Has anyone got any thoughts or suggestions about what I should do next?
Andrew
The motor:
A (late) 2005 Nissan Patrol 3.0D GR (what you call a GU, I think) with a ZD30 engine. It is completely standard - no mods of any kind. It has done 50,000 miles (80,000Km) from new. It starts first time, performance is fine, it uses about as much fuel as Patrol's usually do. It doesn't make smoke or use more than a tiny amount of oil between services.
The problem:
Occasionally & usually up hill under load at 2500-2800rpm there is a sudden power loss. Pressing the loud pedal slowly to the floor achieves nothing. Lifting off restores performance. The ECM stores a 0905 error code (boost pressure)
What have I done so far:
1) Replaced MAF sensor (cheapie off Ebay). Tested new sensor with DMM and measured output volts against engine speeds. It's exactly as it should be (per workshop manual)
2) Replace MAP (boost) sensor. Done by Westway Nissan in Oldham. God those are expensive from Nissan!!! This seemed to cure the problem for about 8 or 9000 miles and nearly 12 months. Just before Xmas 2010, the problem returned.
3) Westway Nissan replaced the MAP sensor under warranty, as it seemed the most likely culprit. It didn't cure the problem. I still have the overboost error.
4) Today, I removed the vac hose from the VNT boost control solenoid, put it in my mouth and sucked hard. The turbo VNT rod moved smoothly to the full extent of its travel. I put my tongue on the end of the hose - and the VNT rod stayed exactly where it was. I gradually released the vacuum and the VNT level smoothly returned to its rest position.
5) I've bought a boost pressure gauge (electronic stepper motor type) but haven't yet fitted it.
What do I *think* I know:
* The MAF sensor is probably OK - I'll test it in the morning again to be sure
* The MAP (boost) sensor is *probably* OK - though I'll test that in the morning too.
* The turbo itself is probably fine - at least the vanes aren't stuck or sticky.
* The VNT actuator works and its diaphragm doesn't leak.
* The vacuum hose to the VNT actuator doesn't leak.
* I don't know how to test the VNT vac control solenoid. Any thoughts?
I know that some of the folks on the forum have cured boost problems by fitting a Dawes valve (whatever one of those is), but this motor has worked fine for over 40,000 miles from new and I'm determined that it's going to work fine again, without making any mods.
One possible option is to give the 'Troll to Westway Nissan in Oldham - and tell them to give it back to me only when they've fixed it. I'm more than a bit nervous of that - the last time they had their hands on it, they tried to clear the ECM error codes with a Consult III & didn't understand why that didn't work. I can just imagine them replacing bits at random until it stops generating the overboost error. No thanks .........
Am I missing something obvious here? Has anyone got any thoughts or suggestions about what I should do next?
Andrew