This is some sort of follow up from the exhaust header change, see link further down.
-- Please subscribe, it's free for you but does really help me to keep this channel going as YT just announced further restrictions to small channels which makes it even less attractive to spend time to produce new content. --
It all started rather suddenly with increasingly poor idle and it was obvious it's running quite rich. OBD system was showing fault code P0171 (too lean) which did not really make sense at first sight.
There are many reasons which can cause this, it just happened that 3 out of the most popular 4 were appearing at more or less the same time.
The fault itself is essentially the same, the engine ECU sees a condition which is not actually reflecting what the engine is doing in reality. This is usually resulting in excessive fuel trims, either lean or rich, so it runs rather lumpy with poor fuel consumption figures. On my 300 mile limp home it did about 8mpg until i pulled the O2 sensor plug to force it running open loop. Definitely not recommended as a general fix as you can easily damage your catalyst if you not careful (at least avoid full throttle) and be sure you know exactly whats going on with your engine !
Because if it's really lean, you'll just kill it within a few miles.
My exhaust header had some cracks (actually leaking quite badly, had already bought the new one) so i assumed that's the reason and changed it .
A leak before the O2 sensor may cause false readings because of fresh air drawn in and therefore raising the actual O2 concentration of the exhaust gas, even the engine may run perfectly at lambda 1.
So far, so good,...but the problem was still there ... OK next, fuel pressure, ... well, that was low, filter very dirty, actually too dirty for the miles, perhaps i had a few poor batches of fuel somewhere.
Still not quite right, ... It turned out that the O2 sensor had a temperature related fault, the hotter it went the leaner it was reading, at higher load (=higher EGT) it was reading zero volts.
So i changed it as well and everything seems back to normal again.
Looking at the big picture, it is quite possible that a poor batch of fuel poisoned my lambda sensor.
As mentioned towards the end of the video, the only sensor i had on hand was a somewhat questionable "emergency spare", meanwhile i fitted a new Bosch sensor and it behaves exactly as expected.
For those who interested in what pulling the O2 sensor plug does ...
(This applies for the 4.0 ltr ERH engine, others may do differently)
Pulling the plug, forces the ECU running from a default fueling map, solely relying on manifold pressure, throttle position, coolant temperature and engine speed. It also retards the spark advance by a few degrees, keeping the EGT cooler at higher load. The engine will not reach max. power in this condition. It obviously reports a lambda sensor fault.. it most likely gets you home, but use your butt sensor and listen to your engine,... sorry, can't really explain that sort of sense, but if you don't know what i mean, you probably better call the RAC for a tow anyway.
Exhaust header part 2
• Jeep Exhaust Header ch...
(c) 2017
www.dynoguy.co.uk
Disclaimer:
This footage is for entertainment only, it may show poor and/or unsafe/dangerous practice.
Always consult an expert first. I must not held responsible if you kill/injure yourself and/or others,
also not for any damage whatsoever.
Негізгі бет Автокөліктер мен көлік құралдары Jeep 4.0 Engine Fault Code P0171 (too lean) but runs very rich - Reasons and how to fix it
Пікірлер: 40