THP Engine fault P2177 - Mixture regulation fault : Mixture too lean.

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lancia58
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THP Engine fault P2177 - Mixture regulation fault : Mixture too lean.

Post by lancia58 »

Hi,

Referring to my post

viewtopic.php?f=3&t=61276

Replaced the whole timing gear ( chain, tensioner, chain guides, bolts, all 3 gears ) including the 2 sealing ring of the VVT gear ( at the inlet camshaft ) to make sure all parts related to the timing are replace. I noticed some improvement in acceleration . After driving about 100 KM I felt that the ECU put the turbo in limp mode and lack of power but check engine did not lit. I hocked my Lexia did a global test and the following fault in the injection read "Temporary fault mixture regulation fault mixture too lean" P2177. I checked the details and found up that the fault was triggered when car speed was zero i.e when stopping. I erased the fault and the turbo came back to life - after two days the fault triggered and again it was when car speed was zero.

After the timing gear was replaced the mechanic drove the car for 100 km at sea level roads and all was well. I drove additional 100 km at sea level roads from the garage to the city I live and all was well.
I live in hilly city ( part of the city is 150 meters above sea level ) and after driving up hill and down hill ( about 6 km ) the fault triggered again. I hooked the Lexia cleared the fault and after 2 days of driving inside the city ( up hill down hill roads ) no more than 30 km the p2177 triggered again. So my observation is that it triggers when car speed is 0 and when driving up hill and down hill. I am not sure the fault is related with driving on roads that are 150 meter above see level , but it happens much more frequent. And all times it happens the car speed is 0.


The details of the error as I copy from the Lexia:

Fault code: P2177
Engine speed: 790 RPM
Engine coolant temperature: 87
Vehicle speed: 0 kph
Inlet manifold pressure: 540 mbar
Richness regulation status: Closed loop
Calculated charging value( filling ): 27%
Quick richness corrections ( row 1) : 8 %
Slow richness corrections ( row 1) : -23 %


Any ideas

Thanks
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xantia_v6
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Re: THP Engine fault P2177 - Mixture regulation fault : Mixture too lean.

Post by xantia_v6 »

I would suspect a vacuum leak, was the inlet manifold removed?
Also check the PCV hose to the manifold at the back of the engine (if fitted), I have heard of them splitting when disturbed.
lancia58
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Re: THP Engine fault P2177 - Mixture regulation fault : Mixture too lean.

Post by lancia58 »

Np the inlet manifold was not removed. I thought about vacuum leak and sprayed a carburetor cleaning spray around every suspected place for leak expecting the engine to rev higher for a short while if the spray is penetrated to the inlet path due to a vacuum but it did not happen the engine revs steadily. I guess this procedure is not 100% checking for leaks. The interesting fact is that the fault is triggered only when vehicle speed is 0. Can one of the sensors give wrong values ? Reading the causes for this fault indicates it may be an injector but than why does it happen on 0 speed ?

Thanks
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Re: THP Engine fault P2177 - Mixture regulation fault : Mixture too lean.

Post by xantia_v6 »

I did a bit of web searching, but there don't seem to be many confirmed cures for that fault code on the EP6 engine. Some claim that it is due to a slight valve timing error (which might be relevant in your case), others that it is a sign of a failing high pressure fuel pump.
lancia58
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Re: THP Engine fault P2177 - Mixture regulation fault : Mixture too lean.

Post by lancia58 »

The high pressure fuel pump was replaced a month ago with a genuine new one. The whole timing gear was replaced a week ago. The only clue I have is that the ECU triggers the fault only when vehicle speed is zero.
lancia58
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Re: THP Engine fault P2177 - Mixture regulation fault : Mixture too lean.

Post by lancia58 »

Hi

The following is from Citroen service net got from a friend who has an account. There are too much suspected parts to replace. Have to bet on the best guess



Image

This is the P2192 it is not the one I have but same suspected cause

Image
lancia58
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THP engine - Turbo in limp mode no fault is logged in the ECU

Post by lancia58 »

Hi,

Yesterday the ECU put the turbo on limp mode again. I hooked a Lexia and I expected to read the P2177 fault and clear it to take the turbo out of limp mode as I did before. See my thread

viewtopic.php?f=3&t=61359


The weird thing is that no fault is logged, the check engine ( orange ) is not lit but the turbo is in limp mode. I talked with a mechanic who is an expert with the THP engine and he told me he has never faced such a thing. He recommended to go to a dealer garage and check if there is a SW update for the engine ECU. But up till month ago the car was OK with the current SW.

Any ideas ?

Zohar
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Re: THP Engine fault P2177 - Mixture regulation fault : Mixture too lean.

Post by GiveMeABreak »

Zohar - please don't keep creating additional posts for the same topic - I've deleted the other thread as it was a duplicate of what you have posted above.

Well you really need to start looking at the P2177 fault suggestions and work through them one by one.

You have access to Lexia, so start doing some live parameters data tests and save the results. You should be able to check reference values against actual data - i.e. the upstream downstream oxygen sensors.

See my post here - although that post concerns a diesel engine, the video (also another vehicle) shows the data stream example that you can check...

viewtopic.php?f=3&t=61170&hilit=downstream#p589811
lancia58
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Re: THP Engine fault P2177 - Mixture regulation fault : Mixture too lean.

Post by lancia58 »

Marc,

The problem now is that no fault is logged. It is very weird thing is that no fault is logged but the turbo is in limp mode

Zohar
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Re: THP Engine fault P2177 - Mixture regulation fault : Mixture too lean.

Post by GiveMeABreak »

Well if you keep clearing the fault codes then it may take certain conditions for the fault to be logged again.

Not all faults are recorded all the time. Some 'faults' need to occur several times, for so long, and can depend on data from other sensors and whether the engine is at a certain temperature and engine speed for example. Some faults are temporary and disappear on their own after other conditions are met.

So it may be that the right conditions for a 'permanent' fault have yet to be met. You may need to take it for a reasonable drive for a fault to be logged.
lancia58
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Re: THP Engine fault P2177 - Mixture regulation fault : Mixture too lean.

Post by lancia58 »

Marc,

I got your point. But if no fault is logged how comes the turbo is in limp mode ? The only thing I have in my mind that the ECU brows the faults log history and "concludes" that fault happened frequent and prevent activation of the turbo to protect the engine. Any way this problem with the car is a tough one
Thanks for the advises

Zohar
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Re: THP Engine fault P2177 - Mixture regulation fault : Mixture too lean.

Post by GiveMeABreak »

I really don't think it can do that! - but the engine ECU can engage a backup mode if there is a particular fault to protect the engine.

If there is a physical fault (mechanical defect for example), then it may not of course trigger a fault code as there may be nothing for the engine ECU to detect via any of the sensors' feedback.

Again , you really need to get the Lexia hooked up and set the parameter measurements appropriate to the components listed under the fault code P2177 that I think you said you have. Then methodically go through and compare the reference values with what the live data is reading and see if you can pin it down.
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Re: THP Engine fault P2177 - Mixture regulation fault : Mixture too lean.

Post by xantia_v6 »

If there is no fault code, how do you know that the ECU is in "limp" mode? The power could be reduced by something completely unrelated?
lancia58
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Re: THP Engine fault P2177 - Mixture regulation fault : Mixture too lean.

Post by lancia58 »

Hi

Well the fault reappeared this time it reads PERMANENT: MIXTURE REGULATION FAULT : MIXTURE TOO LEAN and the check engine lit. At previous times it was TEMPORARY so I guess this is the reason why the check engine did not lit. Below is the screen shoot of the fault screen. It can be seen that it happens of idle on speed 0. The Inlet Manifold pressure seems a bit high for idle should be 420-450 mbar. Clearing the fault took out the turbo from limp mode. I checked all parameters that have an expected value an all are OK.


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Re: THP Engine fault P2177 - Mixture regulation fault : Mixture too lean.

Post by xantia_v6 »

Does diagbox give readings for the fuel pressure set-point and measured fuel pressure? if so, can you show us those readings?