C3 juddering/inconsistent idle

Questions specifically about a Petrol powered Citroen C3 (usually engine or fuel related problems).
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My Name: drummerdude

Contributor
Posts: 19
Joined: Mon May 25, 2015 9:40 pm
Model: C3 2002-2005, Original shape model
Year: 2003 (03)
Engine Size: 1.6 (16v)
Fuel Type: Petrol
Mileage: 80000
Trim Level: Exclusive
Gearbox: SensoDrive
DPF: No
LHD or RHD: RHD (UK)

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Hello there,

Just joined the forum, thank you for all having me.

My C3 is idling a bit rough. The rpm needle is bouncing/uneven (between 720-800) and I can feel a slight uneven judder at idle. It otherwise drives fine, good power, excellent mpg. I would like to fix this as it's annoying when stopped and idling, the car vibrates quite a bit too.

I have so far:

*Cleaned throttle body
*Cleaned MAP sensor
*Checked for vacuum leaks
*Serviced (new oil, oil filter, air filter, spark plugs)
*Injector cleaner
*OBD scanner shows no faults
*LT fuel trim is at -1.8
*No difference hot or cold

Only thing I can see is O2 sensor shows as quite uneven on OBD scanner. Sometimes big gaps, but same symptoms occur with it unplugged.

Any help would be much appreciated. Would like to try and sort this out myself if possible. Thanks.
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My Name: C3driver52

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Posts: 2013
Joined: Sat Apr 30, 2011 7:40 pm
Model: C3 2002-2005, Original shape model
Year: 2003 (03)
Engine Size: 1.4 i
Fuel Type: Petrol
Mileage: 79984
Trim Level: VTR+
Gearbox: Manual 5 speed
DPF: No
LHD or RHD: RHD (UK)
Engine name: TU3 (75 PS)
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Hello drummerdude
drummerdude wrote:I have so far:

*Cleaned throttle body
*Cleaned MAP sensor
*Checked for vacuum leaks
*Serviced (new oil, oil filter, air filter, spark plugs)
*Injector cleaner
*OBD scanner shows no faults
*LT fuel trim is at -1.8
*No difference hot or cold
How about the coil pack? Can give poor running. I see you did the plugs.

Try EuroCarParts for prices and parts :)
My Name: drummerdude

Contributor
Posts: 19
Joined: Mon May 25, 2015 9:40 pm
Model: C3 2002-2005, Original shape model
Year: 2003 (03)
Engine Size: 1.6 (16v)
Fuel Type: Petrol
Mileage: 80000
Trim Level: Exclusive
Gearbox: SensoDrive
DPF: No
LHD or RHD: RHD (UK)

Post

Could the coil pack cause an uneven idle but be fine when driving? Anything else I could also check for?

Thanks. :)
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My Name: C3driver52

Guru
Posts: 2013
Joined: Sat Apr 30, 2011 7:40 pm
Model: C3 2002-2005, Original shape model
Year: 2003 (03)
Engine Size: 1.4 i
Fuel Type: Petrol
Mileage: 79984
Trim Level: VTR+
Gearbox: Manual 5 speed
DPF: No
LHD or RHD: RHD (UK)
Engine name: TU3 (75 PS)
Has thanked: 146 times
Been thanked: 78 times

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drummerdude wrote:Could the coil pack cause an uneven idle but be fine when driving? Anything else I could also check for?

Thanks. :)
Well, it wasn't the first thing on my mind, but you have done or checked everything else. I would class the coil pack in the same boat as the plugs.

The throttle pedal could be worth checking too, if this is giving an erratic signal, you may get an erratic idle. They are easy to swap over if you can find another C3.
My Name: drummerdude

Contributor
Posts: 19
Joined: Mon May 25, 2015 9:40 pm
Model: C3 2002-2005, Original shape model
Year: 2003 (03)
Engine Size: 1.6 (16v)
Fuel Type: Petrol
Mileage: 80000
Trim Level: Exclusive
Gearbox: SensoDrive
DPF: No
LHD or RHD: RHD (UK)

Post

I have replaced the throttle pedal and while it has definitely improved the response of the car, it hasn't fixed the idle problem.

Strange thing is if I unplug the pedal the idle is higher and smoother than when it's plugged in.
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My Name: Arfur Dent

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Posts: 3547
Joined: Sat Jul 23, 2011 3:47 pm
Model: C3 2002-2005, Original shape model
Year: 2002 (52)
Engine Size: 1.4 (16v)
Fuel Type: Diesel
Mileage: 100000
Trim Level: Exclusive
Gearbox: Manual 5 speed
DPF: No
LHD or RHD: RHD (UK)
Engine name: DV4 16-valve diesel (90 PS)
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drummerdude wrote:Strange thing is if I unplug the pedal the idle is higher and smoother than when it's plugged in.
With the pedal unplugged the ECU will use a default idle value.

You swapped the pedals over, so its probably not a pedal problem but it could be a cable/connection problem for the pedal.

There was a problem on some early cars where the RHD conversion had a problem with the wiring extension for the accelerator pedal. The fix is to find the plug and socket for the LHD wiring loom for the pedal and its extension loom for the RHD version and cut off the plug/socket and solder the wires directly instead.

The problem gave a throttle control error, which yours doesn't have, so its only a guess :D

P2101 https://citroenc3owners.com/petrol-citro ... 01-20.html
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My Name: drummerdude

Contributor
Posts: 19
Joined: Mon May 25, 2015 9:40 pm
Model: C3 2002-2005, Original shape model
Year: 2003 (03)
Engine Size: 1.6 (16v)
Fuel Type: Petrol
Mileage: 80000
Trim Level: Exclusive
Gearbox: SensoDrive
DPF: No
LHD or RHD: RHD (UK)

Post

Thanks for the reply.

I will see if soldering the wire helps anything. As I said, replacing the pedal helped with the response and acceleration of the car but not the idle.

I went to have a look at the engine bay today and there was an oil patch around the filler cap. So engine oil is now being forced out of the cap. Any ideas? Engine is also making a kind of rattling sound on acceleration.

Strange thing is engine power is still good and so is fuel economy. :?
My Name: drummerdude

Contributor
Posts: 19
Joined: Mon May 25, 2015 9:40 pm
Model: C3 2002-2005, Original shape model
Year: 2003 (03)
Engine Size: 1.6 (16v)
Fuel Type: Petrol
Mileage: 80000
Trim Level: Exclusive
Gearbox: SensoDrive
DPF: No
LHD or RHD: RHD (UK)

Post

I've done a few more tests and discovered if i spray a flammable aerosol spray into the throttle body the rpm increases and the miss disappears. Does this mean it's a problem with fuel supply?
User avatar
My Name: C3driver52

Guru
Posts: 2013
Joined: Sat Apr 30, 2011 7:40 pm
Model: C3 2002-2005, Original shape model
Year: 2003 (03)
Engine Size: 1.4 i
Fuel Type: Petrol
Mileage: 79984
Trim Level: VTR+
Gearbox: Manual 5 speed
DPF: No
LHD or RHD: RHD (UK)
Engine name: TU3 (75 PS)
Has thanked: 146 times
Been thanked: 78 times

Post

drummerdude wrote:I've done a few more tests and discovered if i spray a flammable aerosol spray into the throttle body the rpm increases and the miss disappears. Does this mean it's a problem with fuel supply?
If you increase the RPM with the accelerator to the same level as the spray does, do you loose the misfire?

I am not sure if the misfire goes just because the RPM increases or because you have added 'fuel'
My Name: Missing Lincs

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Posts: 844
Joined: Mon Mar 05, 2012 9:29 pm
Model: C3 2002-2005, Original shape model
Year: 2004 (04)
Engine Size: 1.1
Fuel Type: Petrol
Trim Level: Desire
Gearbox: Manual 5 speed
DPF: No
LHD or RHD: RHD (UK)
Engine name: TU3 (75 PS)
Location: United Kingdom
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I would say not, I think all you're doing is making the mixture richer by increasing the flammable content.

My experience of idle/rough running problems have nearly always come down to the throttle body. Normally these problems generate a fault code, but not always. Either the valve sticks due to dirt/gunge or problems with the position sensor, usually in this case due to wear.
If at first you don't succeed, destroy all the evidence and pretend you never tried :lol:
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