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Old 03-07-2010, 03:34 AM   #1
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revs will not drop

i have noticed that my 1.8 focus does not respond when changing gears, the revs stay high and do not drop, if i dip the clutch the revs also stay at the same and on occasion climb higher, would appreciate some ideas / help


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Old 03-07-2010, 10:39 AM   #2
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Does the car idle normally when at a standstill (at ~750 rpm)? If the answer is yes, check for a binding throttle cable or possibly faulty throttle position sensor.
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Old 03-07-2010, 10:57 AM   #3
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Some people misunderstand the "normal" operation of the ECU while driving to be a problem. Your revs are supposed to hang in the same place for a few seconds, and will hang longer in situations like coasting to a stop in neutral. This is done for 2 reasons- the first is emissions, rapid engine speed drops cause excessive hydrocarbon emissions- or so they say The second reason is that if you are shifting gears it makes for less wear on the synchros, and transmission gears. On some old messed up vehicles, you might've noticed that if it didn't want to go into gear easily, then you could coax it into gear by tapping the accelerator.

On my car, I've noticed that if I coast to a stop in neutral, the engine rpms will hang around 1k or so until a second or so after I come to a dead stop. This has to do with the VSS still giving the ECU a signal that the car is moving, and so the idle doesn't drop down as far.

Now if your rpms are jumping up higher than 2k, I'd think there might really be a problem that can be repaired. First off, I'd make sure that the accelerator cable is working properly and not sticking. If it is sticking, you can lube it with graphite for a temporary fix, but IMO, the best way to repair this kind of problem is to replace the cable after you verify that the throttle plate is not the cause of the sticking.

You should also take this time to verify that everything is connected correctly in the engine compartment as far as the air intake, MAF, PCV, oil breather, and all vacuum hoses. Usually, vacuum leaks cause engine idle drops in EFI vehicles, but it's best to verify that everything mechanical is in proper order before searching for other causes.

If you can't find anything else wrong, then I'd remove the IAC and clean it first. Look for physical damage to the plunger, and clean any carbonized buildup out of the 2 chambers and the intake ports as best as you can with carb cleaner and Q-tips. Clean the shaft, and check for smooth operation of the plunger shaft by pressing it down with a Q-tip. If the operation is not smooth, and you can't clean it into submission, then replace the part. To reinstall, get a paper gasket from the parts store for a few shillings , or make your own from a soda/beer carton.

That should fix any high idle problems that aren't programmed in. Some people might link the TPS to a cause, but I would not replace the TPS until you start having some other signs of TPS failures. You might also have a sticking injector, but that's something you can figure out by checking spark plug deposits- and I'd think you'd have other symptoms as well like sputtering, rough idle, uneven acceleration, black soot pumping out the exhaust with a strong fuel smell, and things caused by having 3 cyls lean, and 1 rich.
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Old 03-07-2010, 11:05 AM   #4
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The "normal idle" question was meant to cover the possibility of a sticking IACV.
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Old 03-07-2010, 03:05 PM   #5
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as posted above...IAC (idle air control valve) or TPS (throttle position sensor)...they should throw a CEL but dont always do.
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Old 03-08-2010, 08:10 AM   #6
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Thanks for info i will give it a try at the weekend when i return home.
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Old 04-26-2013, 04:39 PM   #7
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ford focus wen driving to change gear and revs go up

ford focus wen driving to change gear and revs go up
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Old 04-26-2013, 04:44 PM   #8
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ford focus 1.8 16v on 1999

ford focus wen driving to change gear and revs dont drop
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