207cc, 1.6l petrol, rough idle & stall.

[Colin2206]

Car is a 2008 Peugeot 207cc 1.6 l petrol. It starts easily enough but can idle rough. It can stall when coming down from high revs, or even down from a steady rev. The Engine Management error message comes on at changes in engine speed, with the warning orange triangle. The triangle can dissappear if steady revs are held, like on a motorway.
No faults are recorded/stored. The only thing I see with the basic Code Reader is the Air Intake Temperature seems to be a constant 49 degrees. From Haynes this sensor is integral with the throttle housing. So, what should the Air Temp should be if it is 14 degrees outside, are there any checks I can do on the Air Temp Sensor?
I don't want to be changing the Throttle Housing then find it is something else.
Any thoughts appreciated.

Colin.

[mickthemaverick]

I would suggest a thorough clean of the throttle body with particular attention to the edges of the butterfly which provide the airflow for tickover. If partially blocked that can be the issue when lifting off.

[Colin2206]

Thanks for the reply.
I hope to take the throttle off on Monday and will check as you suggested. Still would like to understand the Air Intake Temperature Sensor a bit more. As I see it, the temp should be outside air + a little passive heating as it passes thro' the engine bay ducting. So a reading of 49 degress seems wrong.
I'll get the throttle body part no. as I'm fed up ordering parts that don't quite fit.

[PaulC5]

The air temp sensor should be as you say, ambient before the engine is first started and then go up a bit as the engine warms up. So in the morning about 10°C before starting. When checked on our cars the sensor is in the MAF (air flow sensor) and would go up by about 20°C as the engine bay warmed up. Cleaning the throttle body/plate might help and also any electrical connections with you saying your sensor is in the throttle body. You probably do not need to remove the body, just its inlet duct and then spray in/wipe with carb cleaner or white spirit/turps to remove any carbon build up.

[Colin2206]

Thank you for you replies.
PaulC5 : The car seems to be repeating what you helped with a few months ago.

The car has at last produced a fault code and some other symtons, a P11A8 code.
This has happened before with this car and disappears after I spend hours checking & replacing the cam sensors, the dephaser sensor, crank sensor, the o2 sensors (both) and removing & cleaning the throttle body. And then the car gets better. I've never found out what the underlying cause is though. Also getting the coolant temp needle acting funny.
I'll check all the sensors and the ECU for any cracks and water ingress.

[Colin2206]

Well, cleaned and checked the dephase sensor, swapped the camshaft sensors and fault codes have dissappeared for now.
Reading the basic Code Reader, the Throttle Position Sensors track each other quite closely (I guess they should), the first, precat, o2 has a consistent voltage and a trim of 14.5-14.9 depending on throttle position which I believe is correct. Collant temp. seems to have settle down but did behave oddly yesterday on a 20 minute drive, not getting fully up to temp, then dropping, then recovering but never getting fully up. On the return journey it behaved perfectly. According to Haynes the thermostat is integral to the large housing which needs to be removed. There seems to be a sensor also. Working on the principle that you fix what you know to be wrong, I'll try and remove the sensor first then thermostat. I guess a dodgy temp reading being passed to the ECU would cause problems with the air/fue; mixture?

[ozvtr]

and a trim of 14.5-14.9 depending on throttle position which I believe is correct.

Long-term fuel trim? 14-15% is a bit high. Most ECU's max out at +/- 25-30%. Less than 10% is OK, less than 5% is good. So 14.5-14.9% probably needs investigating.
If that's the instantaneous or short-term maximum, then that's OK. Short term can be all over the place when driving and it should be!
At idle short term, again, should be below 5%.
You didn't say if the trims are positive or negative.

[Colin2206]

Thanks for that, hopefuly I'll check that today and let you know what I find.

[Colin2206]

Sorry for the delay in getting back. Had a bit of disaster with the coolant temp sensor. It is held in with, well, a kirby grip. I got it off, put is on a magnet to keep it safe and when I went to get it... it was gone. After two failed attempts to get one from ebay, swallowed my pride and got one from the Dealer... just short of £28!
Anyway, someone had been there before me. the harness plug latch was broken and oil/ water on the sensor socket. So cleaned and resealed and took the car for a run. From the OBD2 record the temp fluctuated between 74 - 106 on a 20min drive on dual carrage, 50mph+ and uphill (the 106 degrees was a sharp spike and matches the top of the biggest climb) and the Fuel Trim seems stable around -0.85. The temp gauge really didn't move at all during the drive, but I realise that it is only meant to be indicative.
I interpretate this as the bad temp sensor connection confused the ECU causing the fuel trim to go out?
The rough running continues with the P11A8 & P0014, exhaust camshaft faults. I swapped aroung the camshaft sensors and the exhaust side came back. I'll check the throttle movement tommorrow and then the camshaft timing after that.

Any comments on the readings so far or suggestions appreciated.

[ozvtr]

the temp fluctuated between 74 - 106 on a 20min drive on dual carrage, 50mph+ and uphill (the 106 degrees was a sharp spike and matches the top of the biggest climb)

Is it an electric thermostat or a mechanical one? Outlet temps should be around 90'C +/- about 5'C. It shouldn't fluctuate as much as yours is.

I interpretate this as the bad temp sensor connection confused the ECU causing the fuel trim to go out?

I don't think the engine temp effects the fuel trims. In this case it's basically just used for the engine ECU to determine when the engine is warm enough to go into closed loop mode. It's the thermostats job to regulate the engine temp and under normal circumstances it's fixed at about 90'C. So the engine ECU wouldn't expect the temp to fluctuate dramatically and so wouldn't be required to compensate.

[Colin2206]

Thanks for the reply.
If I have read things correctly, there is a thermostat housing, which is a modrate complicated plastic housing; a union for coolant pipes, a couple of sensors and a mechanical thermostat. Although the thermostat is listed as a seperate consumable, the practise seems to be to replace the housing in its entirety. They are not that expensive, if that is the fault. A bit of a pain to get off. As I intend checking the static timing, because of the P11A8 & P0014 codes, I'll do it then.

[ozvtr]

If I have read things correctly, there is a thermostat housing, which is a modrate complicated plastic housing; a union for coolant pipes, a couple of sensors and a mechanical thermostat. Although the thermostat is listed as a seperate consumable, the practise seems to be to replace the housing in its entirety.

Sounds like it's the Prince engine? What are the 6th 7th and 8th characters of the VIN?
If it's the prince engine you need to be VERY, VERY careful about the thermostat housing that you buy. The Chinese knock offs are only for the turbo (BMW) version and have an extra outlet! Either get the genuine part from Peugeot or just replace the thermostat.

[Colin2206]

Wow, new information, thank you.
Nos are 205. Not really aware of the Prince engine.

Been trying to get info about this housing and thermostat and it seems to be a bit of a mystery. Haven't been able to find a no. for the thermostat which is what I wanted to order before I took off the housing. So I ordered a cheap housing yesterday, now I have to wait and see.

[gwest]

I only realised that I had the wrong thermostat for my 207CC VTi when after fitting it the coolant I was adding was running out over my boots! I added a short length of rubber hose to the open outlet and put a suitable bung in the end.
Regarding your engine running badly a very common cause is fouled VVT actuator solenoid valves. It is not sufficient just to spray them clean- they should either be ultrasonically cleaned or replaced. Their function can be checked by plotting actual vs programmed timing angle on a suitable diagnostic tool.

[ozvtr]

I only realised that I had the wrong thermostat for my 207CC VTi when after fitting it the coolant I was adding was running out over my boots! I added a short length of rubber hose to the open outlet and put a suitable bung in the end.

I ordered a cheap housing yesterday, now I have to wait and see.

Watch out for that extra outlet! gwest found out the hard way.