406 2.0 HDI 90 Idle problem

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Expertamateur
Posts: 20
Joined: 24 Nov 2018, 17:55
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406 2.0 HDI 90 Idle problem

Post by Expertamateur »

Just recently when I lift off the throttle the idle doesn't drop down to normal speed. It seems to hang around 1000rpm. I had this on a previous 406 and I never did figure out how to fix it. The car eventually developed so many faults that I couldn't afford to fix I scrapped it.
There seems to be no simple adjustment of idle speed at the end of the throttle cable and I'm thinking that tinkering with any adjustment might not be appropriate because sometimes it does actually drop down to normal idle of its own accord. This is the wife's car and she finds the idle fault a bit disconcerting and wants it fixed. Can anyone point me in the right direction for a fix? It is a 2001 and although it is certainly a slug it does run well and is economical with no smoke.

Thanks in advance
wheeler
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Joined: 21 Sep 2002, 19:07
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Re: 406 2.0 HDI 90 Idle problem

Post by wheeler »

Have you confirmed that the throttle position sensor has actually fully returned back to its stop position when the fault obscurs by physically twisting it back by hand?
I would also check it with the cable disconnected from it to rule out a sticking cable. The cable is adjustable by re positioning the circlip that holds the outer cable on its stop at the engine bay end.
Expertamateur
Posts: 20
Joined: 24 Nov 2018, 17:55
x 1

Re: 406 2.0 HDI 90 Idle problem

Post by Expertamateur »

Thanks for your response. I am not sure what the throttle position sensor looks like but I will have a look the next time it happens. I should be able to find if something is meant to be twisting back to a static position.
I will investigate further and post an update here.
wheeler
Posts: 6785
Joined: 21 Sep 2002, 19:07
x 701

Re: 406 2.0 HDI 90 Idle problem

Post by wheeler »

Looks like this & will have the throttle cable attached to it.
Can’t remember the exact location on a 406.
Attachments
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Expertamateur
Posts: 20
Joined: 24 Nov 2018, 17:55
x 1

Re: 406 2.0 HDI 90 Idle problem

Post by Expertamateur »

Yes, that is the gadget. Cable adjustment is exactly as you describe. The wheel that the cable turns seems to return even with the cable disconnected.
Typically the idle wasn't playing up today when I had a look. Probably because the engine was just cold started and hadn't been out for a warm up run.
While I was under the bonnet I unplugged the connector on the back of that wheel thingie and gave it a blast of switch cleaner to sort any corrosion on the pins, and did the same with the larger connector going into the side of the air intake tube. (air flow sensor ??) And treated it to a new air filter.
I have the front brakes in bits at the moment and won't be able to do a proper investigation until its back on the road. Currently struggling to source brake calipers for the beast. Too many variants and very poor descriptions of parts advertised online.

Watch this space.