a Nissan Frontier Navara (called a Pathfinder in US I think) which would go into “limp mode” at certain times for no apparent reason, like just when you needed a spurt to overtake some other vehicle - not good for the heart rate. Backing off the throttle and then back on again would sometimes cure it, but not always. Then I got a total limp mode when the engine refused to rev above 1000rev/min, no matter what the throttle setting. Switching off and restarting would cure that.
I went on the UK Navara forum and asked the question. The generally agreed answer is that the Exhaust Gas Recirculation (EGR) valve is the culprit, and that the fix was to blank the thing off with a blank you can get from most online sites like ebay or amazon. The EGR is an emissions thing whereby at certain revs the engine exhaust is readmitted via the intake manifold (can’t remember why, google it). Sounds like a bad idea, doesn’t it - returning shitty exhaust back into your engine? Well, it is in my opinion, no matter how many polar bears it wipes out.
I fitted the blank and hey presto! The truck goes off the grid like lightning, the fuel consumption is better and I’m thinking of increasing the oil change period from 5000 to 6000 km as my engine is going to be a lot cleaner in future. Limp mode? Thing of the past…
One common meaning of limp home mode is if there is a cooling system failure. Basically each cylinder will skip sparking/fuel injecting every other or every Nth power stroke so as to use a charge of fresh air to cool the cylinder. Obviously on multi cylinder engines these happen out of phase so that there is usually some power being developed. As you can imagine this is an awful way to generate power so the car doesn't want to do this long term, but it can do it for long enough for you to get the car somewhere safe with out seizing the engine.
Regenerating the filter will not do anything against this version of limp home mode.
It depends on why the engine is in limp mode. If you have a DPF on your car and it gets blocked that will trigger limp mode. The DPF normally is self-cleaning, but prolonged periods of short journeys/low speed will prevent the DPF from reaching the self-cleaning temperature. The cure is to find a clear freeway/road and drive at 100kph/60mph or more for around 20 minutes or half an hour. Then stop and switch off the engine for a few minutes. When you restart the warning light should be out and power back to normal.
A DPF Filtered vehcle is , has to be furnished with technology to regenerate / clean that filter.
So it will never clog up, unless it has been mis sold and does only short journeys or a fault exists that hinders regeneration . Period !!!
A DPF, is simply a canister which removes soot particles from the engine exhaust gases of diesel cars.The soot is burnt out of the filter, and deposited as ash during long journeys.
My cars is showing DPF faults, what does this mean?
This means the car is not regerating. The soot however, will continue to build up with driving as this is a by-product of the engine exhaust. If initial faults are ignored you may notice some or all of the below symptoms:
· The car will go into a reduced power or ‘limp home’ mode.
· Engine warning lights may appear on the dashboard.
· Smell of exhaust gases in the cabin.
· Decrease in MPG.
It is strongly advised to fix the issue once these are noticed.
You need to have the computer reprogrammed to avoid error codes and to take advantage of the better flowing exhaust.
Significant improvements in fuel economy and power are usually realised.
Be careful a DPF is an important part of the emission control system and is prohibited from being removed in some areas.
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What does removing the DPF do?
Complete removal the DPF is a one time only, four step process:
· Remove the DPF section of the exhaust from the vehicle.
· Remove the Particulate Filter from the DPF Canister, and Re-Install as per factory Installation.
· Remap the ECU to remove software for DPF — Monitoring System, Diesel Injection System, Regeneration Software.
· Erase stored faults in the ECU, and reset parameters
Once these are done, the process is complete. We view this as the only way to really ensure no more issues with the DPF. As a result you will gain more MPG, better torque and drivabilty and of course no more issues with maintenance of the DPF.
Either remove the DPF and replace it with a bypass pipe or cut a hole in it and remove the insides then weld a plate over the hole.
As you may probably know, Diesel engines are a lot more harmful compared to gasoline ones, and that's because of 3 main reasons:
-Nitrogen Oxides (NOx)
-Particulate Matter
-Black Carbon (or black smoke)
As a MOT Tester I can clearly see the difference - cars with DPFs have smoke emissions equal to 0. However, manufacturers are pretty indulgent and allow an opacity for the smoke of approximately 0.5 m-1. Just to make a comparison - Diesel without DPFs are allowed to have between 1.5 and 2.5 m-1 and car which usually fail the MOT emissions test have over 4 m-1 and that's when you see a lot of black smoke.
Diesel engines emit up to 40 times more particulate matter than gasoline ones. By adding a Diesel Particulate Filter, we are basically filtering any sort of particle with the diameter between 2.5 and 10 microns.
Now, some of you will wonder, why are those particles so harmful?
Well, first of all, you inhale them, and they remain stuck in your throat or lungs. The more particles we inhale, the more likely we are to experience lung or throat cancer.
So in order to reduce this, manufacturers came up with DPFs and believe it or not, they're extremely helpful. Smoke is almost zero, particles are filtered, and we have cleaner exhaust gases.
When I disassembled a DPF a few months ago, I was wearing gloves, a safety jacket and a mask and within 15 minutes, my entire skin beneath the safety equipment was completely red and itchy. I had headaches for the rest of the day and I was sneezing a lot.
Imagine having a city like New York or London full of Diesel cars without DPFs. It would be a natural disaster - too much particulate matter in the atmosphere.
Diesel Particulate Filters have been introduced in 2005, and starting with 2010, nearly all the cars equipped with Diesel engines had Particulate Filters.
The DPF gets stuffed with particulate matter from time to time, and they need to be burnt and eliminated. This is called DPF Regeneration and there 3 types of them:
-spontaneous (it happens while you're driving)
-dynamic (the DPF light will appear in the instrument cluster, so you need to drive continuously until it fades away)
-service (manual regeneration through a scan tool)
The best and fastest way to allow the DPF to regenerate while you are driving is to keep the engine at 3000 rpm constantly.
If you don't allow the DPF to perform a regeneration, it will eventually destroy itself, and replacing it will be the only solution.
If you need to replace the DPF, it would cost you over $1,500, so think twice before buying a car equipped with a Diesel engine.
The lifetime of a DPF is around 200,000km. It varies - you could have problems with it within 40,000 km if you only drive downtown for short distances. The DPF doesn't heat up, it doesn't work properly, and it will get damaged pretty quickly.
If you drive only on the highway, you could easily use it for over 350,000km. The average is around 200,000km but it varies depending on the driving style and conditions.
So this is the purpose of a Diesel Particulate Filter - to reduce particulate matter, black smoke, and to make our world cleaner.
