Omega Owners Forum
Chat Area => General Car Chat => Topic started by: terry paget on 08 March 2015, 09:42:19
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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?
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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.
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never heard of this but they say common
http://www.ecutesting.com/rover_fast___eratick_idle_spee.html
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Interesting read, hoody. What plugs you popped in terry?
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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?
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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 :)
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Thanks TB. What do you mean by MEMS 3?
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have you tried the reset for the tps
http://forums.mg-rover.org/showthread.php?t=496574
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Thanks, Hoody. I did the recalibration, but no change.
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Thanks TB. What do you mean by MEMS 3?
Modular Engine Management System :y
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 :-\
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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!
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Thanks TB. What do you mean by MEMS 3?
That's the ECU used.
Its got a throttle cable.
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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.
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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.
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Air leak between inlet manifold & head?
Faulty temperature sensor?
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I've still got a niggling feeling it's the throttle body flap :-\
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Thanks for the suggestions, chaps. I have returned the car to my son, with the tap in the hose to the AICV. This allows me to set the idle at 800rpm engine hot. If I turn the tap closed the engine stops, so throttle flap seems OK, and there is no leak anywhere else. I changed the ECU coolant sensor a week ago, Andy, but nothing changed.
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I am not alone. This man had the same problem.I wonder how it ended.
http://retrorides.proboards.com/thread/159186/rover-speed-mindf-before-mental
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I am not alone. This man had the same problem.I wonder how it ended.
http://retrorides.proboards.com/thread/159186/rover-speed-mindf-before-mental
the thread goes on to say that the cam sensor and TPS have identical plugs and had got swapped during a head gasket change. Swapping them back fixed it.
Have you recently had a head gasket done or removed parts and reffitted them at all ????
Only ask as had another rover once of a similar era that was doing something similar and after a long while found that the throttle position sensor ,and the camshaft sensor have an identical wiring plug .......am sure you can tell we're this is going lol
Anyway it was found that when he had the head gasket done prior to his idle issue they had put connectors on wrong way round TPS switch wiring was plugged into the camshaft sensor and vice versa
Long shot but worth a try and please do let me know if the wiring plugs are the same on your car as it may just be possible that's what it is
stepper motors always go faulty and stick also
I read about these wiring plugs yesterday, so came down the garage today to check mine out. Guess what? They were on back to front! I swapped em over and its purring like a kitten! Flipping unbelievable, the amount of time i have wasted mucking about with that doesn't bear thinking about. Anyway its running super sweet now so next stop MOT station! Cheers everyone!
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Crank sensor and speedo drive are like that on certain Transits; change the clutch and the bloody thing won't start. I swore at that for ages, Rob fixed it in seconds. Which is yet more proof of the value of experience.
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Given the car here has a cam sensor fault and the idle valve isn't working.. I'd say we have a winner there!
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Given the car here has a cam sensor fault and the idle valve isn't working.. I'd say we have a winner there!
Yep,I'd go with that too :y
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Thanks chaps. I'm glad someone had the wit to follow the thread down. Today I got my hands on the Rover again and swifly swopped the cables to throttle sensor and cam sensor. I reset the stepper motor (5 throttle openings and closures on ignition 2), fired up, and I have idle!. So.happy ending and silly me for carelessness. I am surprised that Rover used 2 identical leads and sockets to connect to 2 sensors - see pic - and that engine ran without complaint without a correctly connected cam sensor and throttle sensor. I was unlucky that no-one on either the Omega or Rover 25 forums was aware of this possibility, and lucky that Google directed me to the Retro Forum where someone did.
https://www.dropbox.com/s/p5diab7to1xq5k7/sensors%26connectors50%25.jpg?dl=0 (https://www.dropbox.com/s/p5diab7to1xq5k7/sensors%26connectors50%25.jpg?dl=0)
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Should have mentioned that the cam sensor can be seen hanging on its lead on left of picture, having been removed from cam cover.
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You won't be the first or the last to make that mistake, I expect! Glad to hear it's sorted :y
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I wonder how many left the factory the wrong way round ::)