Rough idle and intermittent auto choke

Hi Guys,

Hoping for some help as i'm at a loss with my 2011 STX Navara auto. Sorry for the long post but have been looking through the forums over the past 2 weeks and figured the more information I can put down the better.

At the moment I have an intermittent rough idle which happens after starting the ute when it has been sitting for a while. i.e drive to work in morning and coming home in the evening.
Sometimes I start the ute and it revs up to 1200 rpm then back down to 800 rpm and I have no problems. Other times it starts and sits at 800rpm and then idles rough until the ute is warm. If i don't drives without stopping for a few minutes I have to keep foot on the gas in fear of it stalling. Just yesterday it started no auto choke and rough idle andI went to stop while driving over a bridge in traffic (After driving for 30 mins) and the brakes bit more than normal (Had cleaned the car the day before and used brake dust cleaner on the mags but don't know if that had anything to do with the brakes biting more) and it felt like the ABS kicked in as I had gone over one of the metal expansion gaps in the bridge. The revs died and after I had no acceleration on the pedal at all but it was idling fine. Power came back on after pushing down a few times only to do it again after I turned the corner. I managed to stop and did the pedal reset and drove 10 more minutes to work. No problems.

In the afternoon it started with no auto choke and rough idle until warm. I took off from the lights (had been driving for 25 minutes through city) and accelerated, as it was about to go into 3rd gear at 40 km/h backed off the gas completely as someone cut in front and the revs just dropped and when stopped it idled rough and stalled.

Reading through there are a few things that could cause the rough idle but I have repaired through Nissan dealer a fair bit so.....

8 months ago I had the ute going into limp mode for no reason. It went into going up a small hill. (I don't tow anything but have a toolbox on the back which weights close to 1 tonne) Went into limp mode few more times so took it to Nissan. (Wish I had read through all this info first)
SCV replaced - Didn't solve the issue
Fuel pump and chain replaced solved the problem.

Last month I noticed the auto choke wasn't kicking in like it normally does, and was due for a service 130K so took it in. They serviced it changing fluids and filter including air filter and battery (As I see these can cause the issue I have) and cleared a code from the fuel system. Has been fine (although the auto choke wasn't kicking in like it used to) until the past 2 weeks where I have this rough idle.

So the past two weeks I have done the pedal reset a few times when the engine was warm and took it for a drive. Put in liqui moly Fuel system cleaner/conditioner. Worked for 3 days then rough idle back.

Since having to replace the fuel pump I have always filled up at a quarter of a tank no lower and used the same gas station. 7-11 mobil. Since I starting reading on here I have changed to Caltex for diesel as few people suggest against 7-11.

I've brought a OBD2 and using OBD fusion (Have an iphone) connected it and found no fault last night although the auto choke kicked in and there was no rough idle. Ute had been sitting in the garage for 3 hours. This morning I started it with the OBD2 connected. No auto choke and it was rough idle. Left it running like that for a few minutes pulled it out of the garage and it stalled. Started it again and took it for a drive, there was a delay with pushing the accelerator and the power coming on for around 30 seconds. Idled rough at the lights, was having to keep foot on the gas. After driving without stopping for a few minutes and the engine warming up it was fine. No fault codes at all

I have been reading loads of posts on this to figure out what could be wrong and in reading I have lost all faith in the Nissan dealer I have been taking the ute to. Feels like I have been conned in replacing the fuel pump!

I only drive in the city. Don't take it off road.

So what I have read on what to do is (No order)
Replace/clean SCV - Done 8 months ago
Replaced fuel pump - Done 8 months ago
Change filter - Done last month
Check MAF sensor - Done very clean
Check air filter - Done clean.


Can anyone help please?

Welcome to the forum.

The very first thing to check is the condition of the o-ring in the water sensor under your fuel filter. I had my car serviced (by a professional) who removed the water sensor, put the new filter in place, did NOT replace the o-ring and this time didn't even click the water sensor into place. I started having difficult starts, rough running at low revs, similar symptoms to yours. It came to a head when I tried my fuel primer and squeezed the thing a gazillion times to see diesel flowing out of the bottom of the filter. Oops!

So, I bought a new filter - a Ryco, not the Cooper that the mechanic had used - and I replaced the rubber O-ring myself (being careful not to damage the plastic of the water sensor where the ring was seated). I did spill a fair bit of diesel on my lawn and now have two lovely dead patches of grass ... it's cheap weedkiller, I've discovered. Anyway, a few pumps of the primer and it went firm as you'd expect, car started and now runs without any trouble.

So, step 1 - check yours!

Problems at idle are almost always fuel related, particularly if everything is working at higher revs (means the air flow is good). It COULD be a faulty EGR valve that's not closing properly and I don't think the 2011 STX had a flow meter in its EGR valve, I think that came in the 2012 model, so if your EGR isn't blocked, pop the gasket out, fashion a copy that's missing the big central hole out of 1mm stainless steel and pop both back in with a little Permatex Ultra Blue Sensor-Safe Gasket Cement on all mating surfaces.

Thanks for the prompt response Tony. I'll give it a go and report back. Thanks again really appreciate this forum and those that post really helpful!!


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