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Old 14th June 2014, 00:52   #76
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Default Re: RPM shoots up when clutch depressed

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Originally Posted by sbalagru6 View Post
Changed the clutch plates during routine service. After that RPM issue disappeared .
The clutch should have nothing to do with your idle unless your gearbox/transmission is loading the engine. The clutch position sensor is usually not a sensor but a switch which usually enables the starter with the pedal depressed or disengages the cruise control.
Problem is the base idle, either the ECU has lost it's setting or something is commanding the ECU to raise idle, (i.e. something other than the obvious vacuum leak etc) or, the ECU is commanding the idle speed control but is unable to bring down the idle.
Sensors have a hierarchy, on startup the ECU generally looks at the coolant temperature sensor (along with the MAP or MAF) to see if the engine is cold or closer to operating temperature. If the engine is cold the ECU commands the idle speed control to increase idle and operates in open loop. Once the engine (and O2 sensor) is warmed up the ECU goes into closed loop and is in full control of the idle, mixture, ignition timing etc.
On a lot of modern cars there is a specific method of setting the base idle and sometimes this can only be done with a sophisticated scanner. So, before you start swapping parts make sure that you have no vacuum leaks, the system is in closed loop, and all your sensors are within parameters.
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Old 14th June 2014, 13:43   #77
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The clutch was changed because it's almost end of life.

Also my understanding is,if rpm sensor is faulty, then this erratic rpm behaviour should have been observed in idling also... Not just while changing gears...
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Old 14th June 2014, 18:38   #78
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Default Re: RPM shoots up when clutch depressed

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Originally Posted by sbalagru6 View Post
The clutch was changed because it's almost end of life.

Also my understanding is,if rpm sensor is faulty, then this erratic rpm behaviour should have been observed in idling also... Not just while changing gears...
The rpm signal is usually generated by the CKP, or is derived by the ECU from a combination of the inputs from the CKP and CMP.

If you could send me or post a pic of your engine, throttle body with ISC etc it will give me a good idea of what we are dealing with as this engine is not in any US model as far as I can see.

Is this what your idle speed control looks like? http://www.yoyoparts.com/oem/8246722...1022012b1.html
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Old 14th June 2014, 19:44   #79
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Default Re: RPM shoots up when clutch depressed

Most older model Fords have this type of ISC (idle speed control), they have been around for ages are prone to sticking/malfunctioning.
I dug this one out of my garage and you can see the black carbon deposits in the air passage inside. Usually all it takes is a good spraying down with some carb/choke/throttle body cleaner (I mostly use some brake parts cleaner after that and then spray a fine lubricant or ATF to keep the parts moving freely).
This is Fords design, cheap and simple - 2 wire.
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Old 15th June 2014, 23:04   #80
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Default Re: RPM shoots up when clutch depressed

Or you could have this GM style IAC (idle air control)
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Old 15th June 2014, 23:18   #81
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Default Re: RPM shoots up when clutch depressed

Next time you guys have an erratic idle problem please try and do a vacuum test before you condemn anything. If you think the problem is in your idle control circuit you can disconnect the idle control valve when the idle is stable. By doing this you are eliminating the idle control circuit altogether and if the idle still goes up then you know it's not the idler air control that is the culprit.

For those of you who've never seen an idle control valve, here is a video to show you exactly how it operates -

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Old 15th June 2014, 23:46   #82
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Default Re: RPM shoots up when clutch depressed

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Originally Posted by DicKy View Post
The clutch, but in my case if i pump the brake pedal when the car is idling(no reason for doing so, but still) the RPM rises a lil' bit. Can't know as i don't have a tachometer, but the car definitely revs up a little when i do so. Is it because of the brake booster working or something? It's a '09 WagonR.
Its common for the idle to be affected a bit when the brake pedal is depressed. This happens because there is a change in the vacuum in the intake manifold, just make sure there is no leak between the manifold and your break booster.
You should have a check valve on the hose going to the brake booster and there is a valve inside the brake booster that could also be leaking. If this is the case it will suck air through the hose and brake booster leading to a higher rpm.
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Old 16th June 2014, 01:32   #83
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I swear, ive owned every Ford Fiesta to date except the latest model and with every single one Ive had problems with the idle valve. On the up, its the only problem ive ever had with these cars and we've owned 6-7 of them, but still. Ford should be able to do better.

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Old 27th September 2016, 15:28   #84
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Default Re: RPM shoots up when clutch depressed

I own a Chevy Optra Magnum 2.0 diesel variant. Last weekend when I was returning to Bangalore from Tirupati, my car stalled in the middle of nowhere at 5pm as the clutch got depressed completely. There was smoke coming out of my bonnet and some burnt smell as well. The whole day while I was driving, I have seen the car rev more than required whenever I accelerate. And finally in the evening the clutch got depressed completely and we were stuck. As I was with my wife and it was getting dark, I was a little tensed and tried reaching out to some contacts I found online in the near by town.
Luckily, a local mechanic who was passing by in his Indica stopped and asked me about the problem. He offered to tow the car to Bangalore using his Indica and after some discussion we finally linked both the cars using a rod and started driving towards Bangalore. All was well till Hoskote (30km to Bangalore) when the tow hook of the Indica was broken due to a huge speed breaker. Finally, had to park the car in a service lane and got dropped in the Indica. Next day, spoke a towing company and got the car towed to the service center.
Now, the service advisor tells me that the clutch plates got burnt completely and they have open the gear box and replace the clutch unit completely which would cost me Rs 30k and also as Optra is phased out they do not have the part readily available and have to get it from Pune which would take around 6 to 7 days.
Does it really cost 30k?? As I have given the vehicle for servicing only a week before this incident, should they have diagnosed the problem which would have avoided such a mess and also the cost?
Expert opinion requested!
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