nissan 3.0lt turbo again

AJB that is exactly what mine seems to be doing except that mine is doing it at cruise, 100kph not towing and not accelerating and all of a sudden it just drops in the revs, i can put my foot on the floor and nothing happens but if i lift it just a fraction and then return it to were it was it will take off again, getting more and more frequent lucky to get 2 k's without having to repeat the process. i know mine is over boosting as it has blown the pipes off the inter cooler twice,

It's probably the MAF sensor, the early ones seem to have a service life of about 80K and play merrry hell with things when they begin to fail. If I were you I'd get Nissan to replace it and get a boost gauge fitted so you can see what is going on. These should cost no more than about $500 all up. Boost should not exceed 17-18PSI whne you really flatten it and about 7 PSI at cruise. If you take a look around on the forums you will see plenty of people actually doing relatively cheap preventative things to protect the investment they have in these vehicles that in most respects are excellent performers.

I went through 2 MAF sensors in about 4 weeks at around the 100000 k mark. When these went on mine there was a drop in power all the time. Once again I was only 20kms from home but it struggled to hold 4th and I was in 3rd all the way to the dealer.
I dont know if yours is an auto or manual but mine being a manual, when it happened and I was trying to work out what was going on, A couple of times I put the clutch in and kept my foot on the accelerator. The engine would hold at about 2800 rpm and was kind of running like it was retarded (in its timing). Once the foot was taken of the accelerator and then back on, the thing went normal again.

The thing that annoyed me was that it would not do it when the dealer had it, I think he did not test drive it in the same conditions so it was difficult. The other thing was that on at least 2 occasions, possibly 3 I went back with the engine warning light on. He plugged his diagnostic reader on and said that it had come up with an turbo boost problem. Then he said see how it goes.

The whole saga has been good for me which sounds strange. I actually like the vehicle and has been a good performer 95-98% of the time. I knew there were problems with them but only after I had bought so also serviced it often especially with frequent oil changes, filter changes etc. It still destroyed itself. My dissapointment is not with the vehicle it is with the Nissan company or at least their Australian arm.

A boost gauge would be a worthwhile addition to the vehicle. Your problem sounds a little different to mine in that mine only did it under load. I cannot remember it happening just cruising along with nothing on the back and lightly loaded.

I bit the bullet and repaired mine as a second hand 3-0GU is worth nothing. A busted one is worth less! So it was worth more to me repaired and the best thing was I bought a better vehicle while it was being repaired. I think you will face the same decision at some time if you keep it. The rebuild cost was about $9000 with a new clutch and a few other things. Changeover to another similar vehicle would have been heaps if I were trading a busted Nissan. Probably might have got a cup of coffee in the waiting room for it!

Think hard about what to do. If you have an escape vehicle that you have doubts about, get rid of it. The worry in the back of your mind is not worth it as the enjoyment that can be obtained from them is out-weighed by the lack of trust in them.

ajb thanks for the input, new maf blocking of egr and lowering of boost all taking place this weekend
Thanks gbish

thanks for your input new maf going in on the weekend. then some of chaz's sugestions will be taking place as well.
thanks again
gbish

chaz, i have read your posts on blocking egr and winding down boost, very well presented , i will be doing this this weekend.you mention a blowby can, can you let me know were i can find one and were they mount.i have also cheecked out your fitting of boost, egt gauges and manual boost control for the turbo can you give me a rough idear what this has stung you and were i might find the equipment
Thanks for your input

Hi gbish,
You can pick up a blowby or catch can at most speed shops that cater for turbo enthusiasts. I found mine on ebay and they usually sell for around $50. Try and find one with the in and outlets on the top and this should reduce the need for a baffle.
This is the best plumbing and location pic I have.

I think it’s important that the can is mounted above the outlet on the tappet cover, or at least have a high point in the hose. The original breather pipe goes down to the air intake plumbing, just after and too close to the MAF.

I found the Dawes Valve on the TDi VW and Audi forums. They have been battling with similar issues for some time and have some interesting solutions that could help us with our ZD30’s. The TDi valve is different to a normal boost controller in that it is specific for a VNT without the wastgate pressure bleed hole and is available from 3 Bar Racing in the USA.
I paid $45 delivered from the US and about another $25 for the quality Italian made needle valve that I use to control low rpm boost. This simple setup allows me to run safer boost levels without any noticeable power loss and no risk of over boosting and having boost spikes of 25psi plus. You’ll find needle valves at most hydraulic and pneumatics’ suppliers.
Once you bypass the VNT solenoid control valve, you will have boost increasing with rpm and load unlike the erratic boost you get from the standard ECU.
This LINK shows the vacuum and pressure circuit.

Chaz

chaz do you know if you need to do any kind of reset on the engine management after you replace the maf?

Gbish, you shouldn’t have to unless you’ve had an MIL or stored fault code, but if it’s not running right, you could disconnect the battery for half an hour or so. The MAF only sends a voltage to the ECU and provided its within the correct range there shouldn’t be a problem.