Delete limp mode

[Iceman]

Well it went limp twice today. Once while pulling out into fast traffic and with nowhere to go. I really hate the limp mode can happen with no warning and no way to cancel it.
Now here is the question, seeing as it is now possible to edit the ecu and mapping etc, would it be possible to just delete the limp mode function, or at least make it a lot more benign?
I think i would rather have something go bang than sit in the path of an oncoming truck with nothing i can do.
Any thoughts?

 

[Rumpig]

I don't think it's possible to delete outright but MAF and EGR faults can probably be mapped off, possibly DPF to. What fault codes show up?

 

[Iceman]

No codes at all. Looking at what is going in with an obd scanner and torque it looks like it just does it for no obvious reason. MIL doesnt come on either and once restarted all is well till the next time.

 

[DieselTuner]

Maybe its not an electrical problem then, it could be the pressure relief valve opening.

Normally you end up with large fuel leak error, but not always.

 

[Iceman]

Does anyone know what pressure the rail should run at? I had a search of the manual but cant find any reference to it.
Relief valve is a possibility. The power delivery is uneven and it goes limp when given a boot full. I did clean the sCV but i have since replaced the fuel filter. It ran great for 150km after the filter change then back to its old ways. Will do an ecu reset again tomorrow and see if that helps.

Lumpy power
Injector noise
Goes limp when pushed

Turbo looks to be boosting fine on torque app approx 18 psi under acceleration

Fuel pressure looks erratic on graph but then i dont know how it should look...
Ill post a pic of the graph tomorrow.

BGD wont have any injectors for seven weeks but the good news is they are upping thier warrenty to three years! Something to do with a new plating process making them much better. Sounds good to me.

My other truck is 41 years old and has never let me down. Im not sure things are going in the right direction!!!

Thanks all, love this forum.

 

[Old.Tony]

Sounds like the Suction Control Valve to me, happened numerous times before.

Remove it, clean it and reinstall it. Don't waste $ on it until you've at least tried that.

Rail pressure is highly variable. Expect around 4,000psi at idle (750rpm), around 10,000psi at 2000rpm. It's the change in psi that gives you the change in rpm. I get those figures while driving, btw - so it's in-gear and motoring along.

Just to be odd: going downhill (engine braking) your fuel rail pressure will be 4000psi+, but your fuel flow rate (Litres Per Hour instantaneous) will be zero, because in that mode the ECU won't instruct the injectors to open and all the fuel is just returned to the tank. Not that this helps you much with your problem, but maybe cleaning that SCV will solve it.

Oh, um ... remove it, wash it in PETROL, shake it dry(ish) then douse it in fresh diesel.

 

[Old.Tony]

Oh and while I'm thinking about it, the whole reason for limp mode is to prevent catastrophic failures. You have the choice of being able to do 2000rpm and get somewhere, or have the thing go BANG on a level crossing.

I'm sure someone COULD remove the 'limp mode' feature, but if I had a choice between having mine go limp or having it explode I'll take the limp option every time.

And yes, for THAT too.

 

[Beergutz]

When are Nissan going to pull their fundamental digit out of their orifice and recall this issue. Would be interesting to see how many accidents have happened due to it. I nearly got cleaned up twice in my old 2.5 stx.

 

[kernels]

Hey Iceman, can you let us know exactly what it is that you are interpreting as limp mode ? I can't quite remember what I read when I scanned mine, but does 18psi sound a little low for the YD25 ?

 

[cafedex]

Hi Old Tony, I find the opposite with the Ultragauge when going down hills it actually shows I'm using more fuel than when driving under light load. Not sure what's going on there ? My fuel rail pressure varies from 4k to 17k depending on engine load.

Dex

 

[4 naving]

The bailies injectors have the shaft coated as well. they claim a 3 year warranty but its useless as it also cites a 30,000k warranty period that would be done in 1 year by most...

 

[Old.Tony]

Hi Old Tony, I find the opposite with the Ultragauge when going down hills it actually shows I'm using more fuel than when driving under light load. Not sure what's going on there ? My fuel rail pressure varies from 4k to 17k depending on engine load.

Dex

The ECU does keep track of the litres per hour, calculated by fuel rail pressure, injector data and the number of times the ECU asks for the injectors to open - so if the injectors are in good nick, the ECU should be fairly accurate. I wonder if the Ultragauge is looking at the fuel rail pressure and the engine RPM and doing a "best guess" calculation?

 

[joe2006]

Hi Old Tony, I find the opposite with the Ultragauge when going down hills it actually shows I'm using more fuel than when driving under light load. Not sure what's going on there ? My fuel rail pressure varies from 4k to 17k depending on engine load.

Dex

My UG does the same. There is a setting for injector cutoff which I tried but it doesn't make any difference and suspect that that function is not supported, when hooked up to the Nav.

Like OT said, it is probably using other information to come up with consumption figures under such circumstances. The manual says that the injector cutoff setting only makes a small difference to accuracy.