Sticking Valve?

[clipper]

So I am living with my 2004 C8 (2.0 petrol) and its mystery Antipollution fault (which the last two times has shown no codes when plugged in to the diagnostics...)

 

But now that the weather has got colder, I am noticing that the engine will refuse to rev just after starting up. It only happens when the engine is cold, and after coaxing the engine with the throttle a bit, it clears and the car drives fine.

 

Investigating a bit on internet it seems that this could quite likely be due to a sticking valve.

 

Is there any easy(ish) way to check if this is the case? A compression test when cold for example?

 

I already know that the repair cost if it is the case will be prohibitive, but it would be nice to get to the bottom of the issue.

Edited October 18, 2016 by clipper

[Simple]

There are many reasons for the Antipollution fault which may not be related to the DPF itself. I have a 2.0 Hdi Automatic and I also had it few times; due to a leaking vacuum pipe, DPF being dirty and needing regeneration and last week it was due to filling cheaper diesel. When this error appears, the car could loose power and refuse to rev above 2K RPM

 

I have a Lexia VCI and none of the error codes helped find the cause of the problems, I had to do perform thorough and lengthy investigations. The easiest was the cheaper diesel, because the error appeared about a mile after filling and the most difficult was the leak, which took months.

 

If you have a Lexia VCI, try regenerating the DPF, if not, run on the motorway about 10 KM at high speed, also ensure your petrol and air filters are clean, your MAF is also clean (do NOT touch it, use a spray cleaner) before you start the expensive route of changing parts.

 

Good luck, Simple. 

 

.

[paul.h]

If the anti pollution message and the engine management light are coming on then surely there must be a fault code stored. What diagnostic tool is being used to check for fault codes ?

 

On a petrol engine you will not have an exhaust dpf, just the catalyst - if this needs replacing then a fault code would be given from the outlet lambda sensor not giving expected values - live data normally would be a steady value if the cat is ok.

 

The tappets are most likely hydraulic ones which may not be pressurising up with cold oil - if so you may notice a tapping noise when cold. If this is the case you could try an oil change and make sure the correct oil is used.

 

Also consider if the engine temperature sensor is faulty it could be giving the wrong fuel/air ratio for a cold engine. If your code reader does live data see what the temperature is - coolant (engine) as well as inlet air temp which could be from the MAF.

[Rookie2]

I have no doubt that somewhere on the forum it has already been mentioned, however, what Paul states about the oil is vitally important. The amount of damage that can be done by using the wrong grade of oil cannot be underestimated. Indeed, a previous owner of a vehicle having used the wrong grade of oil may have already done the damage, but don't let that deter you from using the correct grade now.

 

For what it costs in comparrison to a new engine, drain it, flush it and refill with correct grade.

 

Just thought it was worth a mention chaps.

[clipper]

Good point about the oil.

 

I think I will bring forward the next oil change and ask the garage to do a complete engine flush and perhaps even add a hydraulic lifter cleaning additive.

 

I have no clue if the problem on cold staring is related to the MIL being lit up, but it is the only issue that I have with the way the engine runs.

 

My theory about the valves comes from various pieces of info found on internat, icluding this from a Peugeot 206CC tech forum which s describing exactly the same symptoms in a 2005 2.0 16v car (I don't know if my C8 has this same engine, but I suspect so....):

 

the main cause of this fault we have found out is the hydrolic tappets. 
the oil ways in them have been made to big causing them to drain qiuckly and fill very slowly. worst when starting from cold,mid warm. also makes the car hesitant and fluffy feeling when driving. this gives the apperance and symptom of a mifire(hence i originally changed loads of coils and plugs to try and solve this fault) 
this lack of combustion and other related issues bring on the anti pollution light. 
the peugeout (very good fix )is to fit the tappets from their 1.8 series. 
these make the engine idle smoothly and feels more responsive. 
most main dealers should know of this fix as it was in recent mastertec update files. 
this only affects the 2.0 (rfn) engines 

[paul.h]

I would still check the temperature sensors. Before starting a cold engine they should all be about the outside temp of around 15°C, the coolant one should then gradually go up to about 95°C and the inlet air temp possibly to about 30°C since it will be warmed a bit by the engine.