GU patrol power mood swings

[Hodge]

What would cause the power to fluctuate everynow and then ??
For a while now I've been noticing my patrol's very moody when it comes to power. Sometime's it's like me on monday mornings, other times it loves to get up and dance.
I've been trying to pin point factor's which may cause it. Weather, fuel, if the car's warmed up yet or not, etc... But it's a mixed bag of results, nothing really lines up with sluggish behaviour.

This morning for example, drove it for 45 minutes and it had plenty to give. On the way back, it's as if it's running on 2 cylinders, feels very sluggish. Then, half an hour later drove it again, and it's back to it's normal self. It's just very odd and annoying. I'm not talking great amounts of power missing, but it is definitely there for me to notice the difference.
After I got the exhaust fitted, I didn't get it tuned or anything, but my mechanic recommended I get it done to get everything else up to speed with the larger exhaust, and he reckons mine is definitely overboosting. My gauges aren't fitted yet so I can't monitor anything so I don't know whats happening.
I'm just brainstorming but could it be the MAF sending weird messages to the ECU ? I've got the spray cleaner (CRC), just didn't get around using it yet.

[P4trol]

I would definitely say it is the engine computer affecting it. Whether it is because a sensor is not connected or faulty or affected by some condition like heat soak, I don't know.

[threedogs]

Wouldn't think you are going into limp mode, as the CRD are very tolerant of higher boost levels.
Disconnect the battery and clean the MAF sensor just left of the Air cleaner, re-install when dry.
Check all your vacuum lines for splits or just brittle. Do you have any blowing smoke issues.
might want to change your fuel filter if its been a while.
Maybe its time to fit your gauges to monitor engine function, one less thing

[Clunk]

Get your gauges on and get it tuned

[MEGOMONSTER]

What would cause the power to fluctuate everynow and then ??
For a while now I've been noticing my patrol's very moody when it comes to power. Sometime's it's like me on monday mornings, other times it loves to get up and dance.
I've been trying to pin point factor's which may cause it. Weather, fuel, if the car's warmed up yet or not, etc... But it's a mixed bag of results, nothing really lines up with sluggish behaviour.

This morning for example, drove it for 45 minutes and it had plenty to give. On the way back, it's as if it's running on 2 cylinders, feels very sluggish. Then, half an hour later drove it again, and it's back to it's normal self. It's just very odd and annoying. I'm not talking great amounts of power missing, but it is definitely there for me to notice the difference.
After I got the exhaust fitted, I didn't get it tuned or anything, but my mechanic recommended I get it done to get everything else up to speed with the larger exhaust, and he reckons mine is definitely overboosting. My gauges aren't fitted yet so I can't monitor anything so I don't know whats happening.
I'm just brainstorming but could it be the MAF sending weird messages to the ECU ? I've got the spray cleaner (CRC), just didn't get around using it yet.

I have had similar type experiences but I wouldn't call it sluggish.
Just some days are zippier than others.
Like the difference between No.5 and No.7 on the DPChip.

[Yendor]

I would start by replacing the fuel filter and check for contaminates.

If it still plays up, get the fuel pressure relief valve checked.

[Hodge]

Wouldn't think you are going into limp mode, as the CRD are very tolerant of higher boost levels.
Disconnect the battery and clean the MAF sensor just left of the Air cleaner, re-install when dry.
Check all your vacuum lines for splits or just brittle. Do you have any blowing smoke issues.
might want to change your fuel filter if its been a while.
Maybe its time to fit your gauges to monitor engine function, one less thing

Thanks TD. I'll begin by cleaning the MAF first. No blowing smoke issues, unless I really hammer it, I'll see a little bit then. Fuel filter was replaced 2 months ago, and have since only been filling up at local servo with a large turn-over so, that's unlikely to be contaminated, but never say never.
Being not too mech-minded, I don't fully understand how vacuum lines would affect performance? When I got the car, I realized my clutch was very stiff sometimes, when Nissan had a look at it they thought it could be the vacuum lines. So there is a possibility something is going pear-shaped in that part.

[threedogs]

The vacuum lines are all the small rubber hoses going to turbo actuator and vacuum solenoid just left of air filter box.
should be 3 outlets from memory.
As Yendor mentions contaminates,,,, was the fuel filter dirty when changed,
if running tank right down could be sucking up crud from bottom of tank

[mudski]

Like TD said. Clean the MAF. But if its foobar the cleaner will do jack. What mods have you got besides the zorst? Dawes and needle valve? EGR block?
Could be a number of things. A vacuum leak may cause this but a Faulty MAF could too....

[Clunk]

But wouldn't a decrease in back pressure from having a larger diameter exhaust do this?