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Old 03-28-2007, 08:17   #1 (permalink)
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Tongue Dancing rev counter/engine revving up and down on its own

I have a 1996 N reg' Ford Escort 1.6 16valve zetec.
The problem i have is that the engine seems to rev up to around 2k rev's, stay there for a moment and then drop down suddenly to almost stalling point at 500 rev's and proceeds to dance up and down on its own with absolutely no feet on any peddles. It doesn't do it all the time, only usually after a run down a motorway or when lengthened driving in and around streets when at work. (I use car for work as im a take away delivery driver)
CAn anyone help me? Has it ever happened to you, if so, how did you rectify the problem?
I liken to say that the engine likes to have a sing song every now and again and the rev counter likes to dance along, but thats gotta stop as its using up petrol!!
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Old 03-28-2007, 14:41   #2 (permalink)
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Re: Dancing rev counter/engine revving up and down on its own

I'll take a stab at it by saying it sounds like an idle speed motor problem. Sometimes you can take it off and spray it out with carb cleaner and it will start behaving again. They get carbon build up on them and start sticking a little.
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Old 03-28-2007, 14:44   #3 (permalink)
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Re: Dancing rev counter/engine revving up and down on its own

I have been told by a garage, (that didnt even take a look) that it's probably down to one of the sensors and most likely the camshaft positioning sensor thats knackered. Would this ring true?
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Old 03-28-2007, 15:23   #4 (permalink)
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Re: Dancing rev counter/engine revving up and down on its own

I dont know if the crankshaft sensor would do that. It doesnt sound like thats it. If its just surging up and down and revving high, I would be inclined to think it was the idle speed motor or maybe the throttle position sensor. My thinking and I could be wrong, is that the crankshaft sensor would probably cause it not to even start once in awhile. Sounds more like once it gets warmed up good is when the problems start.
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Old 03-28-2007, 15:31   #5 (permalink)
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Re: Dancing rev counter/engine revving up and down on its own

Yeah, it does sound like its the idle speed sensor maybe, problem started after a new clutch was fitted 2000 miles ago, i have put up with it til now, but there comes a point when it starts to get annoying !
I wonder if something like redex would put it right, maybe if its a build up of carbon. But where would i put a couple of drips of that stuff in? As i'm only used to the old carburrettor engines, (the best and the older the better).
I have added it to petrol before now before.
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Old 03-28-2007, 20:53   #6 (permalink)
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Re: Dancing rev counter/engine revving up and down on its own

You can pull it off and spray it out with some carb cleaner. It should be about an inch round and about 2 inches long with a wire coming out of it. It should be located near the air intake on the throttle body. Normally has two screws holding it on. When you tak it off you will see a small plunger with a spring behind it. Just spray it out good with carb cleaner and put it back on. If it eliminates or improves the problem you found it. If not, it may very well be the Throttle Position Sensor or crank sensor, however I have my doubts that the crank sensor would cause this.
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Old 06-11-2007, 18:07   #7 (permalink)
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Re: Dancing rev counter/engine revving up and down on its own

Mine does the same thing. I drive alot in crawling traffic but find that when I do put my boot down it tends to stick and idle at 1500rpm for a while. If I switch off and back in it sorts it for a while, when I satrt it the rev needle bounces around. If I set off before it stabilises it cuts out when I dip the clutch. I am fortunate enough to work with an ex-ford mechanic who told me to clean out the idle speed control valve, which he did for my. This cured for a good few months. However, I have just gone to do it myself today, my Haynes manual showed me a different part to the one he cleaned out. I called the ford guy and he told me to clean out the small valve at the front of the engine. Done it today (it was clogged up with oil and crap) and it's running like a new 'un again. Don't think it is the Idle speed Control Valve though like he said it was, more like a PCV valve. On the 1.8, facing the engine, at the front, slightly to the right and below the exhaust manifold there is a short rubber hose with a right angle in it going into a small cylindrical metal pipe surrounded by a large round rubber grommet. Pull of the pipe, pull out the valve (no bolts) and give a good cleaning, mine was caked up with oil residue. Disconnect the battery for half an hour, re-connect it and let the engine idle for half an hour. Then take it on a progressive drive (starting with slight revs and building up over a couple of miles) should have it singing in tune again.
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