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Hi folks, Some of you will know that I have an ongoing problem with an overboost error on my Patrol. I've pretty much exhausted all of the options, yet still it overboosts. The MAF sensor is fine, the MAP (boost) sensor is fine, the turbo VNT calibration is OK, the VNT actuator holds it...

Just a thought - but post-98 passenger vehicles will be EU type approved. Wouldn't that cover their exhaust systems & the legality of mods? Andrew

Yes, indeed. I did previously have a duff MAP (boost) sensor. This was changed in April 2010 and the Patrol was fine for quite a while. In December, whilst accelerating hard down the sliproad from Haslingden onto the M66, I got the dreaded overboost/limp. It turns out that whoever...

A TIP: If any of you folks short pins 1 & 8 on the Patrol's 16 pin diagnostics connector to put it into Diagnostics Mode 2 (instead of buying a Consult-Alike) - and if, like me, you've made up a bespoke ODB-II plug containing only the shorting link - then do remember to take it out of the...

This is an August 2005 Patrol with a ZD30. The EGR valve is NOT vacuum controlled. The valve has a stepper motor that controls its operation. The plan is to block the EGR valve next week and re-do the MAF test to see if the oddity at & above 3200 rpm still exists. If the output volts from the...

I don't know yet - but hope to on Monday. I *think* I read somewhere that it's over £300. (but also that for a ZD30 in a Vauxhall van, it's ess than £200) To be honest, I'd rather keep mine stock too - but would be devasted if I installed a new EGR valve and it idin't fix the fault, which is...

They were measured with the car stationary in neutral. A DMM was used at the MAF terminals. Yes, the airflow fall-off is odd. I think that the EGR valve is open at high engine revs (and also at large throttle openings). It should be closed. Uncontrolled exhaust gasses are pressurising the...

Firstly, I don't know anything about dump valves - so I'd have to do some research to understand the implications of what you are suggesting and decide whether it makes sense for this application. Mine is a Y61 with a ZD30, having a VNT turbocharger. Secondly, I need to discover/confirm what...

I think I'm very close now to deciding that I'm going to block the EGR valve. Immediately after that I've some testing to do and then have to devise a strategy for recalibrating the VNT actuator. The recalibration strategy has to involve very small adjustments that can be reversed to the...

I've just finished measuring MAF voltage against engine revs (again!!!) for the original genuine MAF that was in the car from new (for about 40,000 miles). I took about 50 readings and plotted them as a scatter graph in a spreadsheet. Most of the points you can see comprise several identical...

Maybe I'd better give that a miss then :) One thing I've been trying to wrap my head around is that the VW Tdi folks seem to address boost pressure spiking by lengthening the VNT rod - but the Australian Nissan Patrol folks think it's right to adjust the VNT stop screw. I haven't yet...

Not yet. Slowly, slowly catchee monkee ....... I haven't yet obtained the materials to make one. I don't think cutting up a baked bean can is a good enough solution. I'll probably buy a small sheet of 1mm thick stainless steel off Fleabay. I know it's likely to increase boost pressure at...

Mmm .... what a dummy I am. Nissan have those, don't they. They call them gaskets - and I'd need one anyway if I take the valve off. :doh Andrew

Mmmm ...... that's easy enough, isn't it. If I didn't think I might have to buy an EGR valve soon, I'd probably go out and buy a laptop so I could do that. Andrew

That is interesting. I don't think those are very different from the readings I took - about 0.2 V higher than mine up to 2000 revs, but otherwise very similar. How did you produce that? Andrew

Right, folks - MAF sensor. According to the book of words (dealer workshop manual), the MAF voltages should be: The readings I get are: Ignition on: 0.42 v 750 rpm: 1.57 v 1000 rpm: 1.78 v 1500 rpm: 2.07 v 2000 rpm: 2.6 v 2500 rpm: 3.3 v 3000 rpm: 3.6 v 3500 rpm: 3.6 v This is for the...

The smoke alarm on the landing sometimes goes off when we cook sausages - so yes, it works. Andrew

Let's just summarise where I think I am up to in trying to understand what is going on here ........ 1) The turbo itself is probably OK, at least there's no evidence that the vanes are sticking. The VNT actuator itself is holding vacuum. On tickover, the vacuum in the hose from the VNT...

One thing I do know is that the boost is going well over 20 psi under some circumstances and the ECU then generates an overboost error - so the MAP sensor seems to be doing what it should. I'd be more concerned if the boost pressure was way too high and there was no overboost error. I *think*...

I do understand what you are saying and can imagine how to implement it - BUT I cannot for the life of me understand why I would want to do that. :confused: Surely, if I am hiding the true level of boost from the ECU then it doesn't know to generate an (inconvenient) overboost error if the...