Rough Idle and cut out when warm.

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Colin2206
Posts: 5
Joined: 31 Oct 2019, 12:31

Rough Idle and cut out when warm.

Unread post by Colin2206 »

My wife's car is the 207 CC, 1.6 Vti petrol model on 08 plate.
We've had it for a number of years and it has generally run well and is at 100,00 miles now.
It has recently started to run rough on start up idle although it revs up smoothly and runs evenly going down the road. Yesterday though, when warm, it cut out at traffic lights etc. but will restart at the first attempt.
I have taken out and cleaned the spark plugs, checked the gap (although they are the not-adjustable type). No.1 cylinder was very sooty, the others less so but not as clean as they usually are. Checked the air filter, all ok. Still lumpy on start up. I have a basic code reader but no faults are recorded, other than the O2 sensor P0135, pending, which it has had since the last MOT. A new O2 sensor has been fitted, this fault predates the current problem.
Haynes suggests fitting a new seal at the throttle housing, which I try and get this week.
Anyone had this problem before and any pointers on how to fix?

Regards,
Colin.

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Pug_XUD_KeenAmateur
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Joined: 22 Apr 2013, 17:24
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Re: Rough Idle and cut out when warm.

Unread post by Pug_XUD_KeenAmateur »

I don't much understand these modern cars with their fancy electronics and emission systems

....but sootiness on the Plugs suggests its running rich

...and one of the things I did in the quest to track down a rough idle on a temporary vehicle of similar new-ness that I recently owned was to pull off a Hose while idling so that the engine was pulling fresh air for a short period , see if it made any difference; specifically with regard to the EGR.

...in my case I established that if this was playing silly b****rs, it'd cause a rich mixture,

...an easy and worthwhile experiment

In my case doing so made no difference, so I could eliminate the EGR

Don't let it breathe 'fresh air' for very long, just long enough to test it

Also might be interesting to see if its thirstier than usual, to 'Double-Confirm' its running rich

Colin2206
Posts: 5
Joined: 31 Oct 2019, 12:31

Re: Rough Idle and cut out when warm.

Unread post by Colin2206 »

Just an update.
Stuck a bottle of cleaner in the tank, no real difference. Went back to the O2 Sensor fault reading. P0135 which indicates the heater not working. Checked the heater supply and earth and both there but only getting 9v on the supply. Battery is at 12.5v not great but good enough I would have thought. I can't find a decent wiring diagram anywhere, so if anyone has one for the 207, please let me know.
Going to order a seal for the throttle body. I'll clean, check and refit with new seal. Only other items I've been advised to look at are the vacuum hoses, but again no diagrams so don't know how extensive the system is. After that the injectors themselves, I guess.
The original sooty plugs seem to have been a symptom of the problem, now running clean. The rough running seems to have a pattern. When it is running rough at idle, it hunts between 900 to 1300 revs., although when all ok it idles at 800 rev, quiet and steady. Still cuts out when coming down from higher revs. I can manage it if I slow down with the gears so the engine is constantly engaged.
Any suggestions appreciated.

Colin.