Accelerator pedal intermittent no response - C5 2003 2.2 hdi MK1 manual

[chasqui]

The car has done 178000 miles and runs very nicely still.

It has an intermittent problem which only came up about once a week (car was used daily) but now happens at least 2 or 3 times on every journey.

You are driving along quite happily and all of a sudden the car decelerates. If you press the accelerator pedal down there is no response, it continues to lose speed. If you then release the pedal and the push it down again it responds normally and car runs normally. It can happen across all the gears.

I’ve stopped using the car now as it’s dangerous especially as you pull off a junction or roundabout and a few yards later it loses acceleration as explained above.

On one occasion I couldn’t get the power to engage again and ended up coasting down a slight incline and into a parking space - I was lucky.

I have replaced the throttle position sensor with a new one but this has had no effect.

I have used Lexia but there are no fault codes reported.

Is there another sensor on the accelerator pedal itself?

I’ll be grateful for any suggestions!

Thank you in advance..

[GiveMeABreak]

VIN please..... There were 2 types of system fitted depending on build date. - FLy by wire and a mechanical cable type. Once we have the VIN we can determine what you have.

[chasqui]

Thank you Marc

The vin number is VF7**************[VIN obfuscated, can be read by forum staff]

There is a cable linked to the throttle position sensor, I guess coming from the pedal

[GiveMeABreak]

Well that wasn't really much help unfortunately as either type could be fitted - so you'll have to do a visual check to see which you have:

Electronic Type	Mechanical Type with Cable

None of the accelerator pedals are available from Citroen now (NFP)

So I would expect some sort of code to be stored if it is loosing speed - unless the accelerator pedal is faulty (assuming the electronic one) and that it is just thinking you have removed your foot off the pedal so is slowing down. So a careful check of its condition may be in order - but honestly I don't think there is much you can do if the tracks have or are beginning to wear on it, short of replacing it. If it was engine related - again I would expect a code.

[chasqui]

I guess 5 in the mechanical diagram is the cable going in to the throttle position sensor from the pedal?

I’m not with the he car now but I did remember having re attach a cable to the throttle position sensor when I changed it.

There were no faults shown in Lexia at the time though I will check again during the week.

I’ll try to source a used part off eBay to see if that makes a difference.

The car just slowed down without me moving my foot. Pressing down had no response. Releasing the pedal and then pressing down caused it to work again. (Except the one time I mentioned in first post)

Thanks Marc

[GiveMeABreak]

No worries - yes the wire will work on similar TPS in the engine.

[chasqui]

I’m drawing a blank.. tried a second throttle position sensor.. still having the problem.

It’s the mechanical system that’s fitted to my car.

Bloke at the scrapyard suggested could be a diesel pump, turbo or ecu problem, where the ecu is detecting a build of pressure in the turbo and momentarily shutting down fuel for protection hence the deceleration.

Once the gas is off, pressure subsides and then car responds to pedal again. I’m not so sure if to believe or not.

Does anyone have any other ideas?

I’ve again hooked it up to Lexia but cannot see any faults, temporary or permanent.

[myglaren]

Have you looked at the throttle stepper motor?

[chasqui]

No! Never heard of the stepper motor,, where is it? I’ll have to research!

[GiveMeABreak]

Did you tun a full global diagnostic on it and is it detecting ALL ECUs?

[myglaren]

No! Never heard of the stepper motor,, where is it? I’ll have to research!

Not certain but presumably on the throttle body.
Marc will know

[chasqui]

Did you tun a full global diagnostic on it and is it detecting ALL ECUs?

Yes.. all ecu’s detected..

Global test done.

[chasqui]

No! Never heard of the stepper motor,, where is it? I’ll have to research!

Not certain but presumably on the throttle body.
Marc will know

I’ll explore that. Thanks

[Nemo26]

You should hook up your tester and do some diagnostic while driving.

[mickthemaverick]

Sounds like the car thinks its in cruise control and you have pressed the -set button and then the throttle will pick up again. So does it have cruise?