#1: 206 misfire, fault codes, ecu ? Author: jpm206, Posted: Thu Jan 17, 2013 9:04 am ---- I am at the point of despair with my daughter's 2001 206 1.4 manual - can anyone make any useful suggestions. We have had the car since 17K miles, it now has 48K and has been well maintained.
It is fitted with a sagem s2000-2a ecu.
The story :-
Mar 2012 it broke down on the motorway (in rain), classic symptoms of throttle position sensor - would start, could gently lift revs up to 1,500 - 2000 (higher figure when cold - fuel enrichment ?). Bought a small fault code reader - yes confirmed the fault. 2 scrap yard visits and one new sensor later - no change. Began checking loom, all connectors checked - no change. Discoverd the BSI reset thing - bingo, all well.
Nov 2012 - same symptoms but seemed to fix itself after 2 days - no fault codes.
Dec 2012 similar fault - revs to 2,500 - 3,000 then misfire and cutting out. No fault codes. Connectors etc etc cleaned checked - no change. BSI reset number of times - no change. Gave up, to garage for diagnostic - live data showed No1 O2 sensor reading garbage . New O2 sensor - no change but now have fault code for sensor, scrap yard another sensor - no change. Put original back in - still got fault code. Has now developed fault code on vehicle speed sensor and MAP sensor (swapped - no change). Codes have been cleared and BSI reset after every session.
It feels like a 'cascade' failure of the ecu but before I go down that route does anyone have any useful suggestions. I am a very competant DIY mechanic and in 35years of cars this is the first one that has got me stumped.
#2: Re: 206 misfire, fault codes, ecu ? Author: kandlbarrett, Location: SwindonPosted: Thu Jan 17, 2013 11:22 am ---- My understanding of how things work and a basic explanation:-
1) On idle the engine management is usually from MAF and TPS.
2) As revs climb the feedback circuit (lambda sensor) comes into play.
3) Flooring the throttle causes the lambda reading to be ignored as excess fuel is required for brisk acceleration so the TPF becomes primary input for fueling in this situation.
Now the problem with the feedback circuit is that if there is any fault with the engine operation including leaking exhaust then the feedback circuit will try to correct suggesting the fault may be elsewhere. This post may raise more questions than it answers but these can be little beggers!
So if you have the following the feedback circuit will try to correct it as follows:-
1) Leaking injector = excess fuel so feedback circuit (lambda reading) will lean everything off.
2) Air leak in exhaust before lambda sensor and the car will appear to run lean so feedback circuit (lambda reading) will try to enrichen everything.
3) Now a faulty TPF could do all sorts as it could be telling the car that the throttle it is open, closed or anywhere in between. Now I thought that a poor TPF would only affect hard acceleration or idle as the combination of inputs from the MAF, MAP and lambda would take care of things.
It may be worth doing alive read and include a gas analysis at the same time noting:-
* Carbon Dioxide, is an indication of the completeness of burn, the more complete the burn, the higher the CO2 reading.
* Carbon Monoxide, is an indication of the air: fuel ratio, too much fuel results in a high CO reading.
* Hydrocarbons, is an indication of unburned fuel exiting the exhaust, the more incomplete the combustion, the higher the HC reading.
* Oxygen, is an indication of either incomplete combustion or an air leak. Air: fuel ratio too weak, low combustion efficiency and a pre or post- combustion air leak will cause a high O2 reading.
* Oxides of Nitrogen, is an indication of combustion temperature, low compression pressure, retarded ignition timing and rich mixture will all result in lower NO2 readings. When considering carburettor cars or basic injection cars, emission faults are relatively straightforward to diagnose.
That is the problem with modern cars - you have to consider what the car is attempting to do to correct a fault and how that may disguise that fault giving sysmtoms of something else wrong. Finally excess fuel kills sensors and CATS.
I might just throw a new coil pack and plugs at it just for the heck of it! Second thoughts - no I wouldn't I hate diagnosis by component changing. Last edited by kandlbarrett on Thu Jan 17, 2013 11:57 am; edited 2 times in total
#3: Re: 206 misfire, fault codes, ecu ? Author: kandlbarrett, Location: SwindonPosted: Thu Jan 17, 2013 11:55 am ---- Some reading that I found helpful. Doesn't give immediate fix but does make you think a little deeper. I hope it doesn't confuse further.
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