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Another intermittent power loss thread...
Old 28-11-2019, 07:06 AM
Paul T Paul T is offline
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Join Date: Nov 2019
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Default Another intermittent power loss thread...

Hi all, after some time reading these threads, I've decided to join and post one of my own!

My 2009 D40 2.5 started making a arrhythmic knocking sound from the passenger footwell, most noticeable at idle. Checked under the bonnet and narrowed it down to a buzzing boost control solenoid. Whilst waiting for a new one, I thought rather than depositing half my fuel tank in unburnt diesel into the atmosphere, I bypassed the solenoid and connected the main vacuum line directly onto the actuator. Not surprisingly, I had boost again! All was well, and I drove gingerly to try and prevent the turbo overboosting. However, on a hour long journey along the highway at about 90kph, going up a medium incline, I suddenly lost boost. Over the rest of the journey, this got worse and worse, until every time I exceeded 2000rpm under even extremely gentle throttle, the boost would disappear.

Once the new solenoid arrived, I fitted it and it seemed to work ok for 5 minutes (at least at low rpm) but the same problem reared its head under load above 2000-3000rpm (I rarely go over this anyway). Most of the time, I get boost at the bottom end, but it dies just before the point I change gear.

What have I done in bypassing the solenoid? Any ideas? I think is more than a potentially faulty new solenoid...

Thanks for your help
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Old 02-12-2019, 11:31 AM
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Old.Tony Old.Tony is offline
Join Date: Oct 2009
Location: Mid Coast Region, NSW, Australia
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It might be the suction control valve, too. Or the turbocharger itself. We need to check these things.

I have the same model car, so I know the information is available from the ECU. Use an ELM327-compliant OBD2 bluetooth adapter and an Android app called "Torque". Set the app to monitor boost pressure, fuel rail pressure and anything else that goes green in the list when the engine is running and you're interested in. If the boost is dropping, this will show it - you can also get the app to scan for ECU error codes.

So, if there's decent boost at around 1500rpm (the engine is capable of full boost at 1600rpm), your BCS is probably ok. If it's going into limp mode it will drop the boost off too, but we now need to check the turbo itself.

Pop the hose off the front of the turbo and give the turbo shaft a wiggle. If it moves (other than a smooth spin) then the turbo has worn bearings. If the turbo moves fine, the problem is possibly the SCV. A can of good injector cleaner (Liqui Moly Fuel System Treatment is the one I use) will help with that answer, but you may also be noticing the engine not sitting at a stable idle (engine is "hunting" for a stable idle RPM). This is also a sign that the SCV is at least dirty, if not damaged. I bought a replacement off eBay and it hasn't let me down.

My turbocharger, though, is a genuine Honeywell Garrett that we purchased from a mob in Qld - $1400 compared to the > $3K that Nissan wanted. You do have to make sure how many exhaust bolt holes there are so you can get the right unit. This is a last resort, take a look at the cheaper suspects first!

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boost control solenoid, loss of power, turbo boost

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