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[terry paget]

My daughter-in-laws car. I have changed the head gasket, engine runs fine, but idles too fast - 2000rpm. With the hose to the air idle control valve in my hand, putting my hand over the end slows the engine, closing it stalls the engine. So it is not a leak elsewhere. I have changed the AICV twice, with second hand item, then with new.So fault lies elsewhere. I plugged in my Autex code reader, 3 fault codes came up; P0340 cam sensor, P0120 throtle position sensor, P0304 misfire on 4. I cleared the codes and ran the engine. P0340 persisted. I have checked the cam sensor, it is in place and connected. Engine runs fine. Could the idle fault be caused by the cam sensor?

[TheBoy]

My 25 had a failed cam sensor (strangely, since HG was changed), the only symptom was it seemed to be a bitter flatter pulling away. To the point I was convinced the cambelt was a tooth out, but obviously it wasn't.  It was only when I got the Testbook (mine was pre OBDII when I got it) that I found it was cam sensor. Replaced that, and the thing was back to normal.

I bought 2 2nd hand ones, the first one still threw a cam sensor fault, 2nd one didn't.


So, my experience of cam sensor failure is that it just makes it sluggish pulling away. Everything else was perfect. And that the sensor and/or wiring is delicate when aged.

[hoody]

never heard of this but they say common

http://www.ecutesting.com/rover_fast___eratick_idle_spee.html

[Webby the Bear]

Interesting read, hoody. What plugs you popped in terry?

[terry paget]

Thanks for opinions, chaps. I think the ECU testing corrupt ECU theory applies to an earlier engine. This 2004 engine has 2 coils directly above the head, each feeding 2 cylinders, and nowhere near the ECU. I changed the plugs last summer long before the head gasket failure, and it ran well until December.

The cam sensor fault does not seem a likely reason for the idling fault, but something has to be. When I embarked upon the head gasket job I quite expected to scrap the car. It seems daft to scrap it for an idling fault. In the olden days idle speed was just a screw on the carburretor. It still is on my lawn mower. What can it be?

[TheBoy]

Thanks for opinions, chaps. I think the ECU testing corrupt ECU theory applies to an earlier engine. This 2004 engine has 2 coils directly above the head, each feeding 2 cylinders, and nowhere near the ECU.

MEMS 3 then

[terry paget]

Thanks TB. What do you mean by MEMS 3?

[hoody]

have you tried the reset for the tps

http://forums.mg-rover.org/showthread.php?t=496574

[terry paget]

Thanks, Hoody. I did the recalibration, but no change.

[PhilRich]

Thanks TB. What do you mean by MEMS 3?

Modular Engine Management System 

I don't know anything about the Rovers but is yours Fly by Wire or throttle cable? If the latter it may be sticking or maladjusted slightly stopping the throttlebody air flap from closing properly

[terry paget]

Throttle cable. I don't think it is sticking, I have cleaned it up, but will check again. If it is that would explain everything!

[TheBoy]

Thanks TB. What do you mean by MEMS 3?

That's the ECU used.

Its got a throttle cable.

[terry paget]

Bother. there are some on e-bay, but they all seem to need attention of an auto electrician to code them to the car. I began this exercise telling my daughter in law that her car was beyond economic repair, needing a new head gasket. I have changed the HG successfully, car runs well, but it does not idle properly and the heater fan seems to be dead. Heater fans are available on e-bay, but look tricky to change.

[terry paget]

More info. To make the car useable, I cut a bit out of the hose to the AICV and inserted a plastic tap. Now I can adjust the airflow through the AICV. With the engine warm, I closed it down until it idled at 900rpm. In this state the car is direable. Only problem is on a cold start it stalls unless throttle pedal is used to keep it running.
I appreciate this is not an ideal solution, but it confirms that the fault is the AICV not functioning correctly. I doubt it will pass an MOT like this.
I still have the cam position sensor code showing on the code reader. As you say, this is unlikely to be the cause of my problem. Hoody's reference to ECU idling circuit is interesting, but this car has 2 coils above the head, not near the ECU. Car was running OK before Emma gave birth on November 15th. Engine did not run again until FEb 2015. I had a spare lead on head reassembly, eventually traced using photographs as AICV lead; I then plugged it in before starting engine.

I do not understand it, and am at a loss as to how to proceed.  Please advise.

[Andy H]

Air leak between inlet manifold & head?

Faulty temperature sensor?