Hi
This is the problem that i have with my car and i did post something similar a few weeks back about this. I did receive a reply saying that it was normal behaviour, but i'm not sure that it is. Anyway, this is what is happening. When the car is idling it starts to rev itself and the rev counter starts bouncing around very erratically between about 1,200 and just under 1,000 revs.
Even when driving the car i've noticed it. Say i approach a junction and i'm about to stop (the car is in neutral) the car has to have stopped completely before the revs drop from 1,500 to just under 1,000. It feels like the throttle is being held open longer than it needs to be.
I've not long bought the car & straight away had a new cambelt & service & i did mention the problem to the mechanic who reckoned that he'd seen this sort of thing before but not as bad, and that it was probably something to do with the Engine Management?
Has anybody got any idea why this is happening & if it is normal behaviour what causes it? If it isn't normal what can be done to fix it? Does anyone own an escort with the same engine as mine & if so does it do the same thing? I've owned Vauxhall Astra SRI's & Calibra's in the past and none of them have had this type of problem. Anyway, if you anyone can be of any help i'd very much appreciate it, thanks in Advance.
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The thing with the revs holding at 1500 until you stop is correct, to stop it stalling.
How erratically is it idling? My Mondeo 1.8 varies by about 50 revs if that.
Shouldn't it idle at around 850 rpm?
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Hi, Thanks for the reply. Does your Mondeo holds the revs at 1500 rpm until you come to a complete stop? Why doesn't it just drop straight away to the idle speed, wouldn't that be enough to stop it stalling?
The erratic idling does not happen all the time (i should have said that in the first message) but when it does it starts by idling at about 900 rpm and goes up as high as about 1200 rpm, it's like it can't make its mind up as to what to settle on, that's why i think there is a problem with it. Maybe i'll just have to get used to it but i seem to notice it all the time, at low speeds the car feels a bit jerky like it wants to shoot forward cos the revs are at 1500,particulary approaching junctions. I was in traffick the other morning and it was stuck at about 1100 rpm even though i was at a complete standstill. I think the idle speed should be around the 850/900 mark according to the ford manual, if like your mondeo it only varied by about 50 rpm i could live with that. Perhaps i should get the engine management checked out just to rule out any problems?
Thanks again for replying, all the best.
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It could be the oxygen sensor (lambda)?
Have you checked the engine codes for any faults?
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Hi, Thanks for replying. I've not checked the engine codes for any faults. I didn't know it had an oxygen sensor but it's another possibility to research. Maybe it's not a fault at all and i'm being picky but i've driven loads of cars and never noticed something like this before. As i said in the other message i'll probably get the engine management checked out, i know of someone who has one of the gadgets to do it so i may give that a go.
Thanks again for the reply, all the best.
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Now armed with more info from you the delayed return to idle is normal and is to combat excessive hydrocarbon emissions which would be emitted if the throttle closed abruptly. The hunting idle however is wrong and can be caused by a lazy oxygen sensor, faulty airflow sensor or an air leak particularly at the crankcase ventilator valve on the front of the engine at the right hand side of the exhaust manifold.
Andrew
Happiness is a T70 at full chat!
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Thanks for the info Andrew, ok, i'm now convinced about the revs thing (you did reply last time, right?) Now i'm armed with a bit more possibilities, i may yet get to the bottom of the problem!
Cheers!
Happiness is an escort without an idle problem!
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Your problem reminds me of a 1.8 zetec engined mondeo i heard about a while ago.
Like your escort it suffered from an erratic idle. The trouble was caused by a defective vehicle speed sensor in the gearbox confusing the engine management .
hope this helps
steve
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Thanks Steve, That info is useful. It seems like there are quite a few possibilities that could be causing the problem as posted by the other folks above. I shall add yours to the growing list!
Cheers!
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It could be the idle control valve that is sticking due to being carboned up. Remove it and clean it up or get some "10K boost" engine cleaner (£25 a tin) and spray it into the air intake. This stuff will clean the sytem out and restore any lost power through the engine being clogged up.
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