Fault Diagnosis

[Changi]

Hey All,

I've just noticed over the last two days that there seems to be an issue with my engine.

I've just completed a drive from Townsville to NSW while towing a box trailer. During the drive I noticed that my Ute seemed to really struggle putting power down while in 3rd and 4th gear especially uphill.

I especially noticed that the ute seemed to be surging forward then getting pulled back which made for a very weird sensation almost like a concertina effect.

I initially put this down to the weight of the trailer being towed with a motorbike in it however today when I took the trailer off I noticed that this surging / diving effect was still occurring in 3rd and 4th when I pushed the RPM to vicinity of 3000rpm.

I have also recently installed an air to air intercooler for your information.

Anyone got any initial ideas on the problem or had any experience with this surging / diving phenomena?

 

[doc]

Change your fuel filter.

 

[tweak'e]

what model and engine do you have?

sounds like NPS is playing up.

 

[Old.Tony]

I'm betting it's a D22 with a dodgy NPS as well.

 

[hutchie07au]

I have basically identical symptoms on my '05 ZD30. I tried the basic heat switch test thinking it may be the the NPS. But drops revs as it should in each gear. Is it possible the NPS is on it's way out even with it giving me these results.

Any other ideas?

I don't mean to high jack your thread but I'm thinking we have a similar if not the same issue.

 

[Changi]

Yeah I googled surging issues with D22 Navaras (I have the ZD30 motor) and this forum had an article on the issue which described my issue to the T. I am about to try and disconnect my heat switch today and see how it goes.

Also out of interest what does NPS actually stand for?

 

[hutchie07au]

Neutral Position Switch. I'm going to disconnect mine today too. Fingers crossed we both get the results we are after.

 

[tweak'e]

I am about to try and disconnect my heat switch today and see how it goes.

you don't disconnect the heat switch, you disconnect the gearbox neutral position switch.

 

[Changi]

Ok so I've disconnected the NPS at the plug and will be going for a test drive soon. Just out of interest if I wanted to remove the NPS from the gearbox itself and replace it with a new switch, how do i go about removing that little sucker .

I've got a 19mm spanner on the bronze part that connects to gearbox but am a little worried I'm going to round the sucker out.

Anyone removed it before?

 

[Changi]

Cancel that...solution found

 

[Rumpig]

Were always interested in the solutions, care to enlighten us?

 

[fourocker]

Solution to the problem or solution to the removal of the NPS ?
Incidently thanks to this forum I think I've diagnosed the NPS fault on mine, driving home from work yesterday I had the sensation the same as the OP of this post, most noticeable 3rd and 4th, pushed the lever to the side and it seemed to improve, tested with the heat switch at the lights and it was randomly rising/dropping revs, to the OP I believe from my experience the NPS can be intermittently faulty coming and going.
My NPS is disconnected now and the trip to work tomorrow should tell me how it is, just recently replaced the fuel filter so I'm hoping the plunger head on top of the filter isn't leaking air now, had to prime that sucker plenty !!

 

[Rumpig]

When he says "cancel that- solution found", i took that to mean he found the problem and it wasn't what he thought originally. So the solution to his original problem is what i'd like to hear.

 

[fourocker]

Ok I get what you're saying and ditto I like solutions too.
In reference to my other post the trip to work and back with NPS disconnected went well, the ute was smooth and willing.

 

[Changi]

Hey All,

So for those who wanted to know the solution to my issue pretty much here is what has happened.

I confirmed that the NPS was the issue. I did the heat switch test in my garage and found that when I had my heat switch on and put the ute into fourth gear it did not drop back to its normal idle rev count but was stuck on high idle of 1200rpm.

From here I disconnected the NPS by accessing it through the cabin and redid the test. Immediately fourth gear returned to its normal idle range.

I've since removed the NPS completely and ordered a new NPS in which cost me $79 instead of the few hundred dollars I was quoted to have injectors replaced and the NPS replaced. Even then you can get NPS much cheaper from the below link (I just didn't want to wait up to 5 days for the part to arrive).

http://atocauto.com.au/proddetail.asp?prod=32006_23U6A

I have now installed the new NPS and my Navara is back to working a treat. I used a 19mm deep socket to unscrew the NPS from the gearbox after having cut the wires of the back of the NPS. To instal the new NPS into the gearbox I used a homemade 19mm deep sensor socket to screw it in before reconnecting it to the connector.

If anyone was wondering about the deep sensor socket, I simply didn't own a 19mm sensor socket that has a groove cut along its length to ensure you don't crush the wires on the back of the NPS as you put it in. SO I just bought another 19mm deep socket and used an angle grinder to cut a wide enough groove along it to fit the two wires through it.

Any other questions I'll pass on what I learnt.

 

[tweak'e]

excellent, good to hear

 

[fourocker]

Good one, thanks for the update.

 

[Old.Tony]

Thanks for the update, glad to hear it's fixed - and not as expensively as they tried to lead you to believe. I wonder how they'd have felt if they'd done the work only to discover that they hadn't fixed it, and a bunch of guys reading a TEXT description of the problem diagnosed it correctly when they couldn't do it standing there in front of the thing.