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Old 21-06-19, 08:53 AM   #1
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Question RE: 1.6 VTi engine PCV system

Hi there,
I have a suspicion that my PCV system on my Peugeot 207 sw is not working properly. but I do not have any idea on how it should be working.

I am investigating the cause of a high hydrocarbon emission test failure.

so far i tried to find out if there are electronic faults logged (such as misfires, etc). I cannot see any faults, apart for occasional rich mixture intermittent fault P2178. the check engine light is not triggered so I assume that this intermittent rich mixture is caused by something I am doing while I try to figure out what is going on (rather than being the cause of the problem). - I might be wrong on that, so I already ordered new spark plugs, new air filter, oil and oil filter, so it might cure the occasional error.

The reasons I suspect something with PCV/ vacuums and breathers?

The moment I take the oil dipstick out there is a vacuum in there. you can put the finger to cover and there is quite a bit of vacuum.
Also, removing the oil cap while engine running: it is fine to remove the oil cap, however, when I put it back, after a few seconds the engine struggle to idle and most times just completely cuts off. (so punting the oil cap on makes the engine stall

Also, the error code mentioned above only comes after engine stalls (due to some sort of vacuum and or pressure, caused by me taking the oil cap out

I also unplugged the breather pipe (out of the crankcase cover -on the left of the crankcase cover). it seems like some oil is getting into to breather pipe (it is quite oily- not sure hoe much oil is normal to escape that way)

on the same breather pipe (the one disconnected from the crankcase cover) there is a vacuum, and if I put my finger over, blocking any air the engine stalls in the same way as with the oil cap

I have never investigated anything similar so any help will be much appreciated.

As I said I am not ruling out the fact that I can have a leaky injector or a spark-plug that is worn or an obstruction of air. I am working on that possibility but I find it strange that no misfire codes are logged and the rich mixture code is not normally logged unless I fiddle with the vacuums in the engine.

thank you very much for your help
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Old 22-06-19, 11:44 AM   #2
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Hi Lenroc,
I too have the 1.6Vti engine in my 2008 207SW. All the vacuum observations you have made tally with what I've found with mine.

Yes, there is a vacuum formed in the crankcase and it is surprisingly strong. The PCV valve in the rocker cover is designed to regulate the amount of vacuum so that as the revs climb higher the engine doesn't suck too hard on itself!

The oil breathing is a 'closed' system and indeed RELIES on that vacuum being formed. The removal of the oil filler cap with the engine idling will suddenly confuse the ECU as it will instantly affect the mixture and the computer will try to compensate and this can sometimes make the revs climb. Replacing the filler cap will also suddenly confuse the ECU in the other direction so a stall may also occur.

So once you appreciate the nature of the closed system and how the ECU calculates its mixture and emission figures assuming that the crankcase vacuum is there, you can then appreciate how suddenly removing or reinstating that vacuum with the filler cap can affect the engine's running.

In trying to explain your high hydrocarbon test failure it could be a defective PCV valve. It's a rubber membrane that can either leak round the edges or have an actual split in it. Either kind of leak would upset the mixture without necessarily loosing the vacuum.

Last edited by Equinox; 22-06-19 at 11:50 AM.
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Old 23-06-19, 06:30 AM   #3
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After reading your replay, I start to think that the PCV valve is indeed working as it should.
I am about to perform a compression test so I can rule out the piston rings(although I do not have much pressure inside the engine, if anything I have negative pressure since the PCV connected hose is sucking out a fair amount)

On further diagnostic I performed since since my last post, I read the engine parameters when running at idle the oil pressure came out as "overpressure"

so it seems that there is pressure building out somewhere in the engine.

Is there any other breather of some sort? or is the PCV valve in the crankcase the only way out of the engine?

I still have the white smoke out of the engine, and no error code, no MIL light and no clear lead on what can cause this. The engine is running fine, no issue what so ever, no knocks, no strange sounds, no hesitations, no erratic idle, all cylinders fire as they should (i disconnected in turns each spark plug and they definitely work as the should)

It has to be something, I am missing, but honestly, apart from the compression test I cannot think of anything else (i will perform that once my friend will bring his reading tool)

I will keep you in the loop, whatever happens; Thank you very much for reading
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Old 23-06-19, 09:23 AM   #4
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There could be a multitude of reasons for high HC. If there are no codes logged look at live data for injector correction, coolant temp, intake air temp and calculated air mass etc.

Can you get a copy of the original emission fail or retested as the CO and Lambda values can help fault finding. I assume the car was fully warmed up prior to the test, with an italian tune up prior to test it can take a while to light off the cat on some VTI's my daughters old 207 was
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Old 23-06-19, 09:37 AM   #5
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As for the white smoke, are you getting through coolant? if not have you bled the system fully.
It will chuck out white/grey smoke if air is trapped around the sensor as it will overfuel, it looks like HG fail from the tailpipe but its not.
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Old 24-06-19, 05:25 AM   #6
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Quote:
Originally Posted by windy1603 View Post
There could be a multitude of reasons for high HC. If there are no codes logged look at live data for injector correction, coolant temp, intake air temp and calculated air mass etc.

Can you get a copy of the original emission fail or retested as the CO and Lambda values can help fault finding. I assume the car was fully warmed up prior to the test, with an italian tune up prior to test it can take a while to light off the cat on some VTI's my daughters old 207 was
About the emission test: I bought this car, the seller advertised as "good working order but not used, expired MOT"; the guy looked genuine so I trusted him, it was my fault that I did not check MOT history before;
Once I checked on-line all I can see it is the failure due to high HC. I will eventually take it to another test, but I want to try all I can before I will get another failure.
I have no idea if the car was properly hot when they did the test. It looks like a car that has not been drive a lot, and looks like most of the mileage ware from trips of 3-4 miles. so an Italian tune up will probably help, except that I cannot legally drive the car.
My local MOT is less than 1 mile from me so I will book an appointment to have it tested again soon.
I will keep you updated about the values I will get from that;
prior to the test I will try to keep the car running on high revs for as long as I can so it might act like a proper run down the motorway
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Old 24-06-19, 05:37 AM   #7
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Originally Posted by stripe88 View Post
As for the white smoke, are you getting through coolant? if not have you bled the system fully.
It will chuck out white/grey smoke if air is trapped around the sensor as it will overfuel, it looks like HG fail from the tailpipe but its not.
I had a suspicion that there is something in the coolant circuit.
once I got the car it was low on coolant (well below the min)
I topped that up right away, but not bled it properly, just top up to the max mark.
Anther reason for suspecting coolant problems is that I recently had some strange fan behaviour, i.e fun runs on fast as soon as you start the engine cold and in cold weather
I am not sure if it uses coolant, there is no indication of that since it stays stable (since I topped that up it stay at the same level)
there is also no excessive pressure or any bubble on the coolant bottle (except for the normal pressure)

Do you know how to bleed the coolant system properly?
I will bleed that and see what is next
Also another silly question: I cannot take any of the spark plugs out, all my spark plug tools are too big for the job; I tried with a small socket (14 mm long type) but it is too short for the job, is there a special tool or socket I can use?
thank you
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Old 24-06-19, 09:26 AM   #8
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the way I bleed it, engine hot and running and rubber gloves, you will find a valve that looks like a tyre cap behind/left of the battery on bulkhead, release it until you see coolant, screw it back up and squeeze pipes hard and fast, repeat, repeat each time releasing valve. can take a few miles for the ecu to adjust.

spark plugs, magnetic best Peugeot Spark Plug Socket 14mm 12 Point Thin Wall 3/8
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Old 26-06-19, 08:58 PM   #9
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HI
I properly bled the coolant, it is coming all clear. I did a compression test on all pistons and I have about the same pressure on all of them, about 12 bar on 11.8 to 12.2 bar
so a healthy compression.
the spark plugs were black and wet, which indicates rich mixture, or oil burning.
the white smoke is still there, the ECU does not have any codes, no light on the dash.
I have to also do a leak test ( to see if the pressure in the pistons is stable) but apart from that I cannot think of anything else
Except of a faulty ECU, do you know if ECU can be changed on its own (or it needs the kit - usually with dashboard, key, etc)
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Old 27-06-19, 09:42 AM   #10
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You need to see live data readings not just look for codes.

live data tells you what IS happening codes tell you what HAS happened.

Sounds to me the engine is healthy and an italian tune up is all it needs !

Book it for an MOT and go for the longest fastest roads you can on the way there you dont have to go directly
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