2006 Ford Focus 1.6 Ti-VCT - Jerky throttle when closed or almost closed | Technical matters | Back Room Forum

Wed 15 Jun 2016 01:33

2006 Ford Focus 1.6 Ti-VCT - Jerky throttle when closed or almost closed - Adey1981

Hi there guys. I've been having a problem with my mk2 focus since I bought it 4 months ago. Basically when using the throttle pedal, the car's response is glitchy when in low throttle positions.

When I try to press the pedal as gently as possible, it always jerks as if I am being heavy footed, when i release the pedal, the car jerks too. Also, if i try and hold the pedal in as light a position as possible, the acceleration will glitch around, going on and off, sometimes like a small inconsistent twitch, other times its like a cyclic effect where it feels like im gently pumping the pedal. If I accelerate harder at all, it is fine, the car seems to get up to speed really well. This happens in any gear, but of course is more noticeable at lower gears

I'm not getting an EML or any codes from TorqueApp.

I have looked inside the throttle body and besides a slight yellow patina, there is no build of material anywhere that I can see that would restrict the butterfly valve.

Looked at spark plugs, some soot on the thread bases, but the centre and side electrodes and the insulator tips were clean as a whistle, looked very new.

Ht leads to me look brand new, have checked resistance which was something like 7.5, 6.5, 5.5, 4.4. Havent check for shorting/arcing yet.

Coil pack again looks brand new, dont know how to test this.

I want to do a vacuum leak test but, kinda nervous about spraying stuff around the engine.

Does anyone have any hunches for what this could be? I dont want to just send it to a random garage and have them swap parts over until they eventually find whats wrong.

Maybe I could use the Torque App to monitor fuel trims and o2 maybe this would help?

Thanks Guys!

Adey

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Wed 15 Jun 2016 09:47

2006 Ford Focus 1.6 Ti-VCT - Jerky throttle when closed or almost closed - hardway

Hmm,

I thinking a worn throttle pedal sensor,

Wouldn't have to throw up a fault code,

it would still be in spec,

but a worn bit of the carbon track on the TPS would give just the glitch you describe.

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Wed 15 Jun 2016 17:02

2006 Ford Focus 1.6 Ti-VCT - Jerky throttle when closed or almost closed - Adey1981

Thanks for the reply!

Just to confirm, you are refering to the TPS on the throttle body right, not the sensor on the accelerator pedal?

Thanks!

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Wed 15 Jun 2016 19:09

2006 Ford Focus 1.6 Ti-VCT - Jerky throttle when closed or almost closed - elekie&a/c doctor

The tps is part of the trottle body,it is a sealed unit .The accelerator position sensot is the pedal.To be fair,never changed one.I would check for air leaks first.Also check connector to the coil,if it is the type with 4 ht leads.

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Wed 15 Jun 2016 20:17

2006 Ford Focus 1.6 Ti-VCT - Jerky throttle when closed or almost closed - hardway

To be fair to the Doc I've never changed on on this car either!

But symptoms do match,

Only way to be sure is to 'scope the signal.

But go with the Docs suggestion first.

Always test things that don't cost to check.

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Thu 16 Jun 2016 00:01

2006 Ford Focus 1.6 Ti-VCT - Jerky throttle when closed or almost closed - Adey1981

So it would seem that both the Throttle position sensor and the Accelerator position sensor are both built into the throttle body and pedal themselves?

Mmm, I should be able to test both the sensors though hopefully, just unplug them, then probe the connecting pins with DMM whilst actuating them?

Thanks guys

Edited by Adey1981 on 16/06/2016 at 00:04

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Thu 16 Jun 2016 00:19

2006 Ford Focus 1.6 Ti-VCT - Jerky throttle when closed or almost closed - elekie&a/c doctor

I think you will be wasting your time.Unless you have very small pin point back probes,then you are not going to get an accurate reading.Dmm is no good,you need a scope.Using your dmm probes may make the situation worse.the connecting pins are very small and easily damaged.

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Thu 16 Jun 2016 09:03

2006 Ford Focus 1.6 Ti-VCT - Jerky throttle when closed or almost closed - Cyd

I have looked inside the throttle body and besides a slight yellow patina, there is no build of material anywhere that I can see that would restrict the butterfly valve.

Maybe I could use the Torque App to monitor fuel trims and o2 maybe this would help?

Hmmm! That's a shame my first sugestion was going to be to give the thottle body a clean. Crankcase vapours are usualy 'sucked' in here via the pcv system and can gum up the butterfly. It sounds like yours has had a clean aleady. However, this coud just be he problem. If the butterfly has been swamped with carb cleaner in the past it may have damaged the shaft seals. See if you can detect any sign this might be causeing an air leak which would show up more at low throttle inputs.

My other thought is a throttle potentiometer fault. Sorry, you'll have to Google how to test that. You could use Torque to monitor throttle postion?

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Thu 16 Jun 2016 09:18

2006 Ford Focus 1.6 Ti-VCT - Jerky throttle when closed or almost closed - elekie&a/c doctor

Cleaning throttle body/butterfly is an absolute no-no on Fords.The venturi is covered with a special coating to prevent the build up of gum,and it works.There is usually a warning sticker to this effect attached to the throttle body.

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Thu 16 Jun 2016 10:15

2006 Ford Focus 1.6 Ti-VCT - Jerky throttle when closed or almost closed - hardway

The APS or throttle sensor is just a guess from my experience on other vehicles.

I own and can use a 'scope so I would look at the trace,

You Don't and can't unless you buy one and learn to operate it.

You'd be cheaper getting a specialist in.

The only other option is trying to alter the conditions,

Fit a new/S/H sensor and see if there is ANY change,

They're £40 or so on Ebay so less than half that from a breakers,

Without the specialised tools to test the system that would seem to be your only option.

Normally I would't suggest "Parts darts" to fix anything but a S/H sensor is a cheap option just to rule in/out the sensor possible fault.

My local breaker even does sale/return so in theory this cost nothing but your time.

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Thu 16 Jun 2016 17:41

2006 Ford Focus 1.6 Ti-VCT - Jerky throttle when closed or almost closed - Adey1981

OK, guys, it seems I still got a lot to think about here.

Maybe i should do some simpler tests and if I find nothing, then off to a garage, it's just finding a good garage.

Cheers guys

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Tue 19 Dec 2017 23:15

2006 Ford Focus 1.6 Ti-VCT - Jerky throttle when closed or almost closed - Hooch

Hi Adey1981, I am currently experiencing the exact issues that you describe above on my Ford Focus Mk2 1.6 ti-vct. I have searched the internet hi and low for little over a week and only came across your thread today, thankfully. Please can you tell me did you manage to resolve your problem in the end? And if so, How? Any help is appreciated. Thank you.

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Thu 16 Jun 2016 18:09

2006 Ford Focus 1.6 Ti-VCT - Jerky throttle when closed or almost closed - Cyd

Cleaning throttle body/butterfly is an absolute no-no on Fords.The venturi is covered with a special coating to prevent the build up of gum,and it works.There is usually a warning sticker to this effect attached to the throttle body.

Good to know. Cheers

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