D40 V9X Engine Problem

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Andyjo

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Hi All, I recently posted about problems with not being able to start the motor following a fuel filter change despite bleeding etc, a trip to the Nissan garage reveled that I'd managed to get an air lock in the fuel rail, $600 later it is running again. However the reason for the fuel filter change was an attempt to address an underlying problem that has been on the go for a while and it continues.... The underlying problem was that every now and then the vehicle will not accelerate and appears to go into what I assume to be limp mode.

I checked my scanner and had the code P0488 which I believe is EGR issues. Nissan quoted $1700 to replace the EGR valve which they feel is the source of the problem. They explained that changing the EGR valve is a very tricky operation. I continue to use the vehicle but it still occasionally throws the same problem. My immediate questions are, can the EGR error cause the car to go into what I think is limp mode? Once in limp mode can it come good on its own accord or do I need to stop and restart the engine? Will deleting the error code temporarily fix the problem? Can I bypass the EGR by installing a blanking plate and will that solve the problem and would I need to do a remap once the EGR is blanked off?

The actual problem manifests itself as; once started it idles fine, attempt to take off and it may or may not hunt a bit but then refuses to increase the RPM and just limps forward (limp mode?) and thus far after some messing about it appears to clear and run fine. Yesterday departing work I had the start but not accelerate issue, it farted around for about 50 meters then came good, the first roundabout was no issue, the following roundabout I barely made it through as it refused to accelerate, I slipped into neutral revved it a bit, put it back into drive and it drove the remaining 35km to home with no issue. On other occasions I have pulled up at a red light, gone to take off and it won't accelerate but after a tense few minutes it appears to come good again. I'm dreading the day it does it to me while I'm doing a right hand turn across traffic!!

While I'm not happy at the prospect, if $1700 would fix it then I would get it done but I'm not convinced it'd solve the problem. The car is a 2012 STX-550 model with 135000 km on the clock, I've owned and maintained the car since 2013 and until recently I've been very happy with it.

Any similar experiences, suggestions, advice or solutions to my problem would be most welcome.
 

Old.Tony

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An EGR fault will trigger a Check Engine Light, but it shouldn't induce limp mode because a lack of EGR is not a danger-to-the-vehicle fault. More than likely the fault is the SCV, a fault which results in the exact symptoms that you're describing.

The fact that it clears for a time could mean one of two things:

1) It's actually an electrical fault, not an SCV fault. Clean both battery terminals, and inspect the negative battery lead connection on the engine block, looking for corrosion. Unplug and replug the SCV (and EGR valve, while you're at it).

2) The SCV is only partly constricted, and your driving pattern has changed for the remainder of the trip - you haven't used enough throttle to trigger the fault. The first test for this is to get the engine warm on a drive to an 80km/h (or higher) zone, then from a modest speed (say, 50km/h), use over 75% throttle to accelerate. If this triggers it, stop the car, turn it off, and repeat it (to make sure it's repeatable in precisely that way). The second test (is a partial fix) is to either use the Liqui Moly Diesel Purge (an excellent fast-acting process) or put a full bottle of Liqui Moly Fuel System Treatment in the tank and drive for 100-200km. The engine should stop hunting, but the SCV may still misbehave at high throttle and if it does, it's most likely that the SCV needs replacing.

As for the Nissan dealer ... changing the EGR valve is not a "delicate procedure" unless you're doing it while wearing fishnet stockings and suspenders (and if you are, well, good on you, but take care not to damage the stockings). They'll charge you a motza for the EGR valve and try to take one of your children for the labour charge, but in reality it's a few bolts, an electrical connector and some sensor-safe gasket cement.

You may be able to just block the EGR tube altogether by copying the gasket between the EGR tube and the EGR valve, and accidentally forgetting to put that big hole in the copy. If your car has had the flow meter added (more recent models did, I think 2013+ ? ) then it might throw a CEL for blocking the thing, most people drill an 8mm or 10mm hole in the centre of the blanking plate to remedy this.

Come to think of it, the code might be thrown because the EGR is blocked, and that could just be muck in the EGR tube (or a hole in the EGR tube?) or the combination of soot and PCV oil gumming up the EGR outlet to the intake manifold. I didn't think that error would force a limp mode though, but happy to learn about it.
 

The Woo

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If it really is an EGR fault, would it not be a reasonable option to consider a tune that electrically closes and takes the EGR out of the system. A performance tune like that that cost me about $1,200 a few years back.
 

Andyjo

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OldTony, Thanks for your input, I will give your suggestions a try.
Interestingly during all the issues I've had with the vehicle the check engine light on the dash has never illuminated, apart from on startup as per normal.

I tend to agree with you, the EGR code has probably been on the go for a while and is just muddying the water in regard to the limp and hunt issue (incidentally the hunt on initial take off has only occurred twice). After some initial research I too thought it likely that the issue was SCV related, the Nissan bloke said it was highly unlikely?

Just went for another run, it messed around briefly as I left my driveway but came good pretty quickly and didn't miss a beat for the rest of the journey?? Its almost as though it somehow gets some air in the fuel system which clears pretty quickly. Its never had the problem while travelling at speed, it has always appeared on take off from stationary and it occurred initially quite infrequently however the frequency appears to have increased to probably once per journey.

In regard to my earlier questions, if I blank off the EGR with a 5mm bypass hole, do I need to do anything with the ECU? Also can limp mode clear of its own accord, or does it require a restart? The nissan bloke also said there is a software update available, in your experience is it worth going for the update?
 

Jamo

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Andyjo,
I have a 2012 STX. I have had the same limp mode issues, but after a dyno tune. My EGR is blanked.
I have to turn it off and restart it, which generally clears limp mode, but its concerning if towing and you cannot pull over to restart. I found that a good flogging in the sand under full load and full throttle makes it run a lot better. Most of my driving is around town and unloaded.
I’ll keep watch this thread to see if any other suggestions come up.
 

Andyjo

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Jamo,
So your limp issues appeared after the dyno tune, or did the tune resolve the problem? Did you blank off the EGR or was it done previously? Do you get the P0488 code because of it? Is your blanking plate drilled? Sorry for the barrage of questions....

I'm pretty sure my issue is not connected with the EGR problem, car did its limpy mode thing yesterday but cleared after a short while. When I got home I plugged in the OBD2 scanner and zero error codes?

the vehicle gets a decent workout, I pull a 2 ton boat up to Jurien and overtaking road trains often sees it on the matt! I'm not convinced it is going into limp mode, it definitely has previously where I've had to restart to clear it. But the recent events have cleared after a bit of phaffing with the throttle. I need to get some kit so I can monitor fuel rail pressure when the issue occurs.
 
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