Sudden fuel consumption

[peterx]

Hey All,

I've got a 2009 D22 ST-R with the YD25 engine. It's done 220,000 kms, zero problems since I bought it.

When I first got it, it would consistently do 750-800 kms to a tank of fuel, I changed the tyres and that dropped to 700kms to a tank, did over 30,000 kms on those tyres and it's been a pretty consistent 700kms to a tank.

In the last couple of tanks it's suddenly started sucking through the fuel at a crazy rate. 380kms to a tank for one, 400kms for the next, 360kms for the next. All similar routes, no hills, no towing, no new modifications.

I did a reset of the ECU to see if that made a difference, no change. I've changed the air, fuel and oil filters and oil to see if that makes a difference, zero change.

Mods:
- BF Goodrich tyres (265/75/16)
- Canopy
- Steel bull bar
- Narva spotties
- UHF & Mobile aerials mounted on the bull bar.
- Roof racks

Few other mods, but nothing to the engine and those are the main external ones.

I'm at a loss as to why it's suddenly using nearly double the amount of fuel it was previously. Any suggestions?

- paul

 

[Rumpig]

There's people that have had fuel leaks from the spill line inside the rocker cover or leaks from the fuel pump into the timing case. Your oil level isn't going up is it?

 

[Teleman191]

Would it be about time to check the injectors?

 

[Old.Tony]

The fuel HAS to go somewhere unless you've got a stowaway smurf that gets high on sniffing diesel.

If it's going into your sump, STOP DRIVING. Diesel fumes entering the PCV would be ingested by the engine causing run-on - unless you can starve the engine of air, once run-on starts the only thing you can do is get out, walk away and film the inevitable explosion with your camera. Check your oil level pronto!

If it's not going into your sump, check to see if it's dripping off anywhere under the car.

If it's not dripping anywhere, the only other place it can go is out your exhaust. It will present itself as either black smoke or white smoke. Black smoke would indicate that the car's sensing the fuel pressure wrongly, and raising the fuel pressure - it should feel more powerful than it used to be.

White smoke would normally indicate an injector fault, where fuel is being sprayed arbitrarily into the chamber and out the exhaust. Could be the CAT reductant cycle held too long? Almost unheard of, but without knowing more symptoms, we're stabbing in the dark.

I suppose a CAS misalignment would do this too. That would change the timing of the injector pulses, you might notice an increase in engine noise (knocking as the fuel enters the chamber too early) or the extra smoke (or both).

There could be other reasons, and I'm sure Tweak'e, Tappet, Seventies47 or others will be able to offer some ideas as well.

 

[peterx]

I've checked the oil a few times over the last few weeks, levels have been unchanged from check to check. I changed the oil, there was no fuel in it that I could see, zero water there too.

I can't see any evidence of it dripping anywhere.

It does blow a bit of black smoke while accelerating, a bit more than it has been in the past. If I sit on 110kph (GPS not speedo), it blows a fair bit of smoke for extended amounts of time. It also spits out a puff between gear changes some times.

It doesn't seem to be running rough at all, it could be slightly noisier than normal, but not a huge amount, hard to tell really. It's a fair bit noisier than my mates ST-R but he has the 3L engine and it's only done 75,000 kms.

 

[Old.Tony]

Then it would seem that either you've got something wrong in the fuel pressure - perhaps a relief valve not opening? - or a mistiming. If it were starving for air (dirty air cleaner, something stuck in the intake, like a bird gobbled up by the snorkel - it happens!) you'd expect the car's performance to suffer, so I'm thinking more along the lines of overfuelling.

Overfuelling is sometimes caused by a poor sensor return. Now this is where the car's history might help - diesel performance chips USUALLY interfere with the pressure return signal (on CR engines) so that the ECU thinks the rail pressure is lower than it actually is. This causes the ECU to raise the pump output to the point where the rail pressure is being reported as what the ECU expects - when in actual fact the rail pressure is higher. When this happens, you feel the extra power. So there are two specific questions here: does the car feel more powerful, and do you know if the car has ever had a chip on it?

Mistiming should make the car feel less powerful, like you have to give it more gas to get the same output as you used to. It's not unheard of for the CAS to slip or have metal fragments interfere with it.

So, how does it feel when driving? Like it used to?

Also, when you're @ 110km/h and it's blowing smoke, what colour is that smoke?

 

[bods]

I'd try some injector cleaner first. It might have a bit of a sticky injector if it hasn't ever had them looked at, which might be leaking after injecting fuel. If no luck with injector cleaner it would probably be worth getting them looked at, that's quite a lot of km if they have never been touched...

 

[4BYFOR]

I just made a thread on the liqui moly injector cleaner and it's worked a treat for me, solved the excessive black smoke and runs much smoother.. Cost you about 30-40bux all up defiantly worth a shot mate.. I can't believe I didn't know about it earlier!

 

[peterx]

So there are two specific questions here: does the car feel more powerful, and do you know if the car has ever had a chip on it?

Never had a chip on it as far as I know, I bought it 2nd hand at around 90,000kms 2.5 years ago.

Mistiming should make the car feel less powerful, like you have to give it more gas to get the same output as you used to. It's not unheard of for the CAS to slip or have metal fragments interfere with it.

So, how does it feel when driving? Like it used to?

Also, when you're @ 110km/h and it's blowing smoke, what colour is that smoke?

It feels like I have to give it a bit more in order to take off, not a huge amount, but definitely more than I used to. I assumed that the tyres I put on 30,000kms ago may have something to do with that as I lost a little bit of fuel economy when I put them on too.

The smoke is always black, I've never seen any other colour come out of it. I really only notice it at night if there is a car behind me with it's lights on though. It's pretty thin, not huge clouds of it.

 

[Old.Tony]

Then I'd try the injector cleaner, in particular the one 4BYFOR recommends. If it doesn't improve things, you can knock "dirty injectors" off the list of possibilities (which is reasonably high on the list, really).

If it's only a marginal performance loss on takeoff then it probably isn't a CAS issue, it's most likely in the fuel quantity - so that's injectors or sensors.

If it were a sudden drop, it would have to be either caused by a particle (foreign matter, even water in a CR injector) or an electrical issue. How about unplugging all of the injectors and replugging them (repeat each one twice) to clean the contacts, then do the same for the pressure sender and then over to the ECU, do the same thing there? Make sure you have your radio PIN handy for that.

 

[peterx]

I'll give it a shot, the liqui moly diesel injector cleaner is the recommended one right?

Any guides or manuals on unplugging the injectors etc, I'm not real familiar with the diesel injectors, but I know my way around an engine bay.

I've installed an aftermarket CD/MP3/Bluetooth headunit, so no pin issues there

 

[peterx]

Just found the service manual, downloading it. I'll pull them out tonight

 

[4BYFOR]

I did a short video on Facebook and posted it in the thread on how to with the link from liqui moly site for the diesel purge

http://www.navara.asia/showthread.php?t=26862

I hope it works for you mate it made a huge difference in my ute.. But give me a week and I'll let you know if my mileage gets better as I only get about 500k from a tank

 

[Old.Tony]

Oh don't unplug the injector, just its electrical connector. Should be up the top, vertically over the pistons.

Unplugging the injector rail is definitely not something to consider doing lightly and I wouldn't suggest it unless you had a workshop at your disposal (plus spares). There's not a lot of room for error when you're dealing with a rail that has to contain up towards 30,000psi (1700BAR).

 

[peterx]

Ah yes, that's some pressure I really don't want to mess with

I'll do the electrical connectors shortly.

I ran through some of that Liqui Moly just before my last Pilbara trip.. about 25,000kms ago, I'm pretty certain it's the same stuff anyway. I'll try it again though.

 

[4BYFOR]

Ah yes, that's some pressure I really don't want to mess with I'll do the electrical connectors shortly. I ran through some of that Liqui Moly just before my last Pilbara trip.. about 25,000kms ago, I'm pretty certain it's the same stuff anyway. I'll try it again though.

Was it the system diesel purge moly or did you put it in with a full tank of fuel?

 

[peterx]

I didn't put it in the fuel tank, I stuffed a pipe from the fuel filter into it (just 1, not both) when I was changing the fuel filter. I'll try it again with both pipes stuffed in there.

 

[peterx]

I pulled the MAF sensor out this morning and gave it a clean, it was pretty grubby. Filled up, went for a 100kms drive, filled up at the same pump Used 10.6L, much better than the 17-18L it was using per 100km.

I've not cleaned the injectors yet, but will be doing that this week as well.

 

[happy john]

You don't say if it's down on power but i would suggest a weeping injector take it to a specialist.

 

[peterx]

Nearest specialist is nearly 300kms away in Perth.

It doesn't feel like it is down on power, maybe a touch sluggish on take off, not a huge amount though.