Loss of acceleration/power in first gear only

[leigh]

Hello. First time poster, new to the forum. Thank you for having me.
I have read over the forum and spent hours looking for a solution to my problem. A lot of similar issues but can't seem to find an exact match.
2011 D40 Navara - randomly loses power and has zero acceleration in first gear. I can have my foot flat to the floor and it won't go any faster than walking speed. I then have to quickly put it in second gear for it to start picking up again. Even when in second to fifth I can still notice a loss of power but it is at least driveable and can get to normal speeds.
The strange thing I am finding is when the engine is cold, it works perfect. Full power and no issue. It is when the engine is warm, that I am getting the issue. It is driving me crazy and I hate driving it as I can't trust it.
After reading the forum, I have done the following:
EGR Blank
MAF Cleaned
ECU Reset
None of these things have worked. I am not a 'car' person so what I have done is straight from advice on this forum then doing it after watching YouTube.
I did take it to my local mechanic for a diagnostic and no codes were coming up. They were of the opinion it needed new fuel injectors and SCV, quoted me around 6k. I'm not paying 6k so will happily try to fix it myself. Most of the similar issues I have read about in the forum don't mention the fuel injectors? Apologies for the drawn out post.
Any advice would be welcome, thank you in advance.

 

[Old.Tony]

I'd not touch the injectors yet either.

Usual culprits for this sort of behaviour:

* Gearbox neutral position switch (NPS)
* Suction Control Valve (SCV)
* Turbocharger control (boost control solenoid or BCS)
* Turbocharger
* EGR valve

Here are some things to try.

1) Take the car for a drive. Put it in first gear and pull the clutch out to get moving. Now hold the gear lever to the left or right without popping it out of gear. Any improvement? If it is "fixed", it's your NPS. You could just unplug it and the problem disappears.

2) If the problem goes away after turning the engine off and returns only after using high throttle it's a sign that the SVC is suspect. First thing to try is a bottle of injector cleaner in the tank.

3) While it's unlikely to be the BCS, it's worth trying this: find the small hose that comes across the top of the motor and connects to a black widget sort-of halfway between the alternator and the left headlight. Make a note of where this went. Remove the same sized small hose off the top of the turbocharger (there's a round thing attached to it - this is the actuator). Put the first hose onto the actuator and drive the car. If that fixes the problem, the BCS needs to be replaced. Don't drive too much like this, put the hoses back the way you found them.

4) Undo a hose clamp on one of the big hoses that go from the turbocharger up towards the front of the engine bay (it doesn't matter which as long as you can pop the hose off and wipe a CLEAN finger on the inside). Your finger should come out with a black oily stain on it. Examine this oily stain under a very bright light - do you see any sparkles? If so, your turbocharger is suspect and needs to be checked.

5) EGR is a PITA (pain in the a---hole). It's difficult to tell if the EGR valve is working properly or not without some good diagnostic equipment and patience, but you could just blank it off and be done with it. On the intake manifold side (vehicle right hand side) is a connection where the gold tube that runs around the front of the motor joins onto a widget. The widget is the EGR valve. Undo the two bolts (12mm spanner) and be sure to catch the gasket - you need to make an exact copy of this gasket (use 1mm stainless steel or 1.6mm mild steel plate) but without the big hole in the middle. Reassemble with your copy of the gasket instead (or as well, it doesn't really matter) and try driving the car. If this worked, forget it - you've got a busted EGR valve and there's no need to do any more, you just fixed it.

 

[leigh]

Thank you Tony for the detailed response, really appreciated.
I finally worked it out.
I couldn't understand why it would lose power, mainly late in the day or night but be fine in the morning (upon start up) and majority of the day.
I had to go out last night and the same thing happened (as usual).
The only thing I could think of that I was doing any different from day to night was using the headlights.
So, while I was driving (walking) in first gear I turned the headlights off, and BOOM, the car took off...
Put the headlights back on at the next stop and back to walking. Lights off, back to normal.
Whoever put the driving lights in must have done something weird with the wiring and it has caused this ridiculous scenario.
Now I just need to work out how to fix the problem. Very happy I found the cause, it was literally driving me crazy.
Hopefully this fix might help someone else who may be experiencing a similar problem.
Thank you.

 

[nudge2325]

Mine had a short in the trailer wiring that caused the same issue

 

[leigh]

How did

Mine had a short in the trailer wiring that caused the same issue

How did you diagnose where the short was coming from? Did you need an auto elec to find it?

 

[nudge2325]

How did

How did you diagnose where the short was coming from? Did you need an auto elec to find it?

I found it by accident one morning pulling up to a shop and saw the parkers come on when I put the brakes on.
Removed the trailer connection and problem solved.