Strange boost issue

[docp1980]

Hey guys,

Noticed a weird issue with my boost this morning. I've been running a dawes/needle setup set to 20 psi now for almost a year without any problems. This morning I noticed my boost gauge only running out to 15-16 psi and then while under load at times I would apparently lose all boost (according to the gauge). I have checked all of my hoses and can't find cracks anywhere. The Dawes and needle valves are still set exactly how they always have been. The only thing I could think of is that the connection directly behind the gauge may be loose, but if that was the case, surely it should happen all the time? Could there be an issue with the turbo?

Any help appreciated.

Cheers,

Matt

[threedogs]

check and/or re fit all the hoses. No idea what you drive but is your IC oily at all.
Forum needs as much info as possible

[4bye4]

Mate if you are loosing all boost on the gauge but its still driving OK it's got to be the gauge. What about EGT's? If the boost really is all over the place the performance and EGT's would be all over the place too, maybe even engine lights and limp mode wouldn't it?

[Hodge]

Maybe something is up... I mean if it's only getting 15-16 instead of 20, it's high end boost difference of 4psi, so you may not be noticing much performance difference . Just throwing it up there.

[threedogs]

Also if its loose at the gauge the needle may flutter and also make a noise

what year and motor is it???

[mudski]

Seems to be a boost leak to me. If it is, the issue will worsen over time as the hole gets bigger. Check the underside of the intercooler for oil wet spots. This is a tell tale sign of a leaking intercooler. Check all your hoses and clamps too while your there.

[docp1980]

Cheers for all of the responses. EGT's are still fine 200-300 oC most of the time. 2013 GU series 9. Haven't checked the underside of the IC, i'll do that next. The strange thing is that sometimes it is fine, other times it will appear to hold boost and then the gauge drops back to 0, even though it's still under load.

[mudski]

What brand gauge do you have? Is it a capillary type with a hose running into the cab? Or does it use an electrical sender?

[docp1980]

Autometer ultra lites. Hose running into the cab.

[mudski]

Hmm i would be checking the hose going from the motor to the gauge aswell.

[threedogs]

Bumped any update yet,??

[docp1980]

Still trying to sort it out. Just realised I can check the boost on my scan gauge so that will tell me whether it's happening at the manual gauge on in the intercooler/MAP sensor as the scan gauge reads from that.

[docp1980]

Looks like the gauge is the problem as my scan gauge is still showing full boost at the MAP sensor, even when the gauge drops to 0 and i'm also seeing differences in boost level between the MAP reading on the scan gauge and the gauge (taking into account the 14.9 PSI atmospheric pressure reading). Will check the O-ring under the MAP boost line adaptor and also pull apart the Dawes to look for any obstructions this weekend.

[threedogs]

Very rare but sometimes the ball in the Dawes doesn't seat properly.
but do one fix at a time till you find it

[docp1980]

Very rare but sometimes the ball in the Dawes doesn't seat properly.
but do one fix at a time till you find it

So it's been over a month now and I still can't find the problem... Pulled apart the Dawes valve, it was clean as a whistle. Reassembled, problem still there. Took the boost valve adaptor off the intercooler, o-rings look fine and were seated correctly. Checked the intercooler, no sign of oil on the underside, catch can seems to be doing its job very well.

What I can't understand is how the issue corrects itself after say 15-30 mins of driving. So especially from a cold start i'll accelerate and the boost on the gauge will not spool up at the normal rate, hit about 15 PSI (Dawes set to 20) and then just fall away to 0. The turbo is still working though as the power doesn't drop off but the induction noise and the delivery of power just isn't the same (sounds a lot rougher) as it is when the boost gauge shows everything working nicely. In addition, I have noticed that my EGT's seem to be lower when accelerating with the boost gauge showing 0, which sounds like the turbo is working harder? What then happens, is if I get on the freeway and tap the throttle on and off and few times, the gauge will then return to normal and everything goes back to being fine. Another thing I have noticed is that comparing the MAP sensor reading to the boost gauge, the readings are pretty close when the boost gauge is functioning, but when the boost gauge reads 0, the MAP just goes straight to 22 PSI boost (taking into account the atmospheric reading) and doesn't deviate until you stop accelerating.

All hoses appear to be fine and if it was a hose leak, you wouldn't expect the problem to correct itself or for the strange rough acceleration to occur. Same with the gauge, if that was the problem, then it should be dodgy all the time. Once it corrects itself I can drive for hours without it reoccurring.

Any help would be greatly appreciated as it's driving me nuts and i'm at the point where I think i'll need to take it to United Fuel Injection to see if they can solve it.......

Cheers,

Matt

[threedogs]

Cheapest option IMO would be to maybe get it Dynoed, just a thought

[4bye4]

Can you disconnect the boost gauge at the motor end and block the hole where the sensor screws in. Then just drive it for a while and see if the fault goes away or no. At least you will have eliminated the gauge from the issue.

[mudski]

Have you tried a new maf?

[boots]

Tested your intercooler for leaks ?

[the godfather]

So it only happens when it is cold right?
I would be looking for a fracture somewhere, maybe in the little plastic vacuum tank under the IC.
They also have a one way valve in them that can play up occasionally.
I will try and post a picture of the unit.
They are $95.00 from Nissan. I just replaced mine because it was perished.

[the godfather]

58977
My understanding is that if this little tank (actuator) is faulty you get mixed signals going over the place.
If it completely fails you loose all your turbo boost.
Best thing would be to rip one off a mates car and try it on yours (or vicar verse).

[docp1980]

So, I took the car to United Fuel Injection who dynoed it and could not find a problem, except they said my boost gauge was faulty as there's worked fine. I then bought bought a new autometer gauge; same problem still there! I have also re-run the boost line to try and rule this out. Any one with any other ideas? I'm at the point of just re-ordering the complete dawes/needle system again and replacing it!

[threedogs]

Im thinking you have a cheap nasty needle vavle,
they are prone to failing and hard to diagnose.
I brought my needle vavle from Dependable in SA
I take it its a Common rail 3ltr??

[mudski]

So it only happens when it is cold right?
I would be looking for a fracture somewhere, maybe in the little plastic vacuum tank under the IC.
They also have a one way valve in them that can play up occasionally.
I will try and post a picture of the unit.
They are $95.00 from Nissan. I just replaced mine because it was perished.

Those vac tanks are prone to breaking yes but its something you just throw away and by pass anyhow. They're not needed and we removed from the Patrol from about 2002 I think....
To the OP. What type of needle valve are you running? Also, if the maf is faulty, you will see similar issues. A member here had similar issues and it turned out it was the maf the whole time. Plus I have seen happen to other Patrols, including CRD's.

[threedogs]

Pretty sure the OP has a 2005 or later so the vacuum can is not an issue as you say.
Only saying that as he has a scan gauge,

[docp1980]

Needle valve is a top quality Tognella one, bought from Dependable. Patrol is a 2013 CRD, so that vac tank shouldn't be the issue. Based upon the fact that this just happened out of the blue after a year of running fine, I am inclined to go with the faulty MAF sensor suggestions. Does anyone know how much a new MAF is going to set me back? The Patrol is still under warranty, so if I put the boost back to vacuum/ECU control and take it to Nissan would they be able to diagnose the faulty MAF? Thanks heaps for all the suggestions!

[docp1980]

$200 for a genuine Nissan CRD MAF from Nizzbits! Damn! I don't suppose anyone in the Perth area would have a spare MAF I could put in to see if that's the problem?

[mudski]

$200 for a genuine Nissan CRD MAF from Nizzbits! Damn! I don't suppose anyone in the Perth area would have a spare MAF I could put in to see if that's the problem?
$200 i would say that's a direct injection maf. The crd mafs are around $300. Give or take....
If you cantry a maf first that would be ideal.
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[mullet_hunter]

Can u post a vid of your scan gauge in real time? My autometer gauge n ecu talk gauge are both identical for psi readings...
Also what happens with ur boost in standard configeration.. ie hw much boost etc.. hw much valts u getn at maf sensor?..

Heres all the possible problems..

Test intercooler for leaks in bucket of water.. block both ends n preasurerise with bike pump or if you use an air gun be carefull to only feather the trigger...

Reinstall all intercooler hoses..

Double check all vac lines...

Clean/replace maf sensor...



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[the godfather]

Anymore news on this issue? Curious to know what t was.

[docp1980]

So it looks like i've finally resolved this issue after some advice from a member of another forum. He suggested that it was probably spooling up too quick, so I set the needle valve back two settings and everything is fine again. I can't believe it was such an easy fix, and it never occurred to me that would be the problem as the setting it was on had been fine for a year and I still can't work out how the increased spool rate could cause the boost gauge reading to drop to zero...... Also, the car never went into limp mode when it happened (well by that, I still had acceleration, but the engine just sounded alot rougher). Anyway, if this happens to anyone else, there is an easy fix!

Cheers, Matt.