fast idle staying on when the engine is hot

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xantom
Posts: 65
Joined: 26 Aug 2008, 14:33
Location: Near Lincoln
My Cars: Renault 16 - my first car bought secondhand in 1980. Lasted a couple of months before dreadful rust brought it to an end.
Renault 18 estate petrol. Bought in 1981. only new car I've ever owned and only because it was tax free to Forces in Germany. Lasted 18 months before accident write off.
Renault 18 saloon petrol. bought in 1988. lasted 3 years before accident and repair cost ended it.
Xantia Esate TD. Bought in 2006. First Citroen and bought because of the suspension and potential to run on veg oil. Apart from a stint owning a doomed C5 estate I've owned nothing but Xantia TD saloons and estates since. All have Bosch pumps so veg oil since 2006 for me.
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fast idle staying on when the engine is hot

Post by xantom »

I've got a Mk1 1.9TD Xantia with a fast idle that stays on when the engine is hot. I've checked out the vacuum diaphragm and it works because when I rev up by pulling the throttle lever I can see the diaphragm pull the fast idle lever back. The problem is that it doesn't do it when the car is at normal operating temperature, as I believe it should and as it does perfectly in my identically set up Mk2 1.9TD. I'm assuming that this must be a problem with the ECU not sending input to the small switch on the vacuum piping when the temp is up even though it activates the switch, and thus the vacuum, when it senses increased engine revs. Does anyone recognise this and is there a cure? It's not just that having a constant 1050-1100 rev tickover is a bit annoying it is a bit wasteful on fuel, although I can fairly clip along a level road in 3rd gear with my foot off the accelerator. As a thought, is the engine temp sensing for the idle speed done from the temperature sensor on the front of the fuel filter housing, and what is the sensor at the back of the housing for? Could this be a culprit?
Tom
Tom
1998 Xantia Mk2 1.9TD Saloon
1996 Xantia 1.9TD Estate Mk1
(Previously Old Guy's)
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CitroJim
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Re: fast idle staying on when the engine is hot

Post by CitroJim »

Tom, yes, you're right. Fast idle is the default and vacuum is needed to pull the idle down to norrmal.

Have you checked that manually pulling on the fast idle lever brings the idle down to normal?

The electrovalves used to route the vacuum to the diaphragm capsule and the EGR valve are identical and can be swapped over for a test but before you do that, check the vacuum pump is working and see if vacuum is present at the diaphragm capsule when the engine is warm. You can use the tip of a finger over the ends of the pipes to 'feel' the vacuum.

A duff temperature sensor could cause it and a Lexia or ELIT diagnostic will quickly tell if the ECU is giving the correct signal to the electrovalve.
Jim

Runner, cyclist, time triallist, duathlete, Citroen AX fan and the CCC Citroenian 'From A to Z' Columnist...
xantom
Posts: 65
Joined: 26 Aug 2008, 14:33
Location: Near Lincoln
My Cars: Renault 16 - my first car bought secondhand in 1980. Lasted a couple of months before dreadful rust brought it to an end.
Renault 18 estate petrol. Bought in 1981. only new car I've ever owned and only because it was tax free to Forces in Germany. Lasted 18 months before accident write off.
Renault 18 saloon petrol. bought in 1988. lasted 3 years before accident and repair cost ended it.
Xantia Esate TD. Bought in 2006. First Citroen and bought because of the suspension and potential to run on veg oil. Apart from a stint owning a doomed C5 estate I've owned nothing but Xantia TD saloons and estates since. All have Bosch pumps so veg oil since 2006 for me.
x 3

Re: fast idle staying on when the engine is hot

Post by xantom »

Thanks Jim. Yes I've pulled the lever mechanically and it works. In fact it was when trying to adjust the annoying constant fast idle I discovered the vacuum only kicks in to pull off fast idle if I increase the revs with the throttle lever. This makes me think that the electrovalve is working but isn't being told to when the engine is at normal temp. I think you're right and I will have to arrange the car's first lexia diagnostic. More pressing at the moment is that the rear O/S piston has been chipped a bit at the neck (concussion freeing of piston for removal - it works a treat for me but if you're clumsy it can damage the neck of the piston). Now the rim holding the seal has a small bit missing so the LHM pressure bulges the seal out and it leaks. I tried using a "harder than steel, sticks to anything' material to fill the rim breach which worked well for a year but the other day I ended up going through a rather deep flood. The scab I'd put on must have had bit of thermal shock and split off. Always embarrassing to arrive home on a pick up truck. Anyway, my second repair was fine until I decided to replace the rear spheres this morning. My concussion freeing technique freed more than the piston and so now I'm doing a third repair. I'd really like to replace the piston, and I have another Mk1 for spares, but I can't get the pin out that retains the piston rod end against the suspension arm. I am scared of breaking it in place. Do you know of any clever techniques to get this old pin out? I imagine I'll need it to get the replacement piston off the spares xantia too.
Tom
1998 Xantia Mk2 1.9TD Saloon
1996 Xantia 1.9TD Estate Mk1
(Previously Old Guy's)
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CitroJim
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Re: fast idle staying on when the engine is hot

Post by CitroJim »

That's a problem with the suspension cylinder :) Personally I've been very lucky and have never had to go there but I know many have and there are, I'm sure, methods. I don't know them but I'm sure someone will soon divulge a good method. If not then pose the question in a new thread.
Jim

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Re: fast idle staying on when the engine is hot

Post by DickieG »

xantom wrote:I've got a Mk1 1.9TD Xantia with a fast idle that stays on when the engine is hot.
Is the air conditioning turned on and/or the heater lever set to demist? The reason I ask is that when the A/C runs it also activates the faster idle speed.
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xantom
Posts: 65
Joined: 26 Aug 2008, 14:33
Location: Near Lincoln
My Cars: Renault 16 - my first car bought secondhand in 1980. Lasted a couple of months before dreadful rust brought it to an end.
Renault 18 estate petrol. Bought in 1981. only new car I've ever owned and only because it was tax free to Forces in Germany. Lasted 18 months before accident write off.
Renault 18 saloon petrol. bought in 1988. lasted 3 years before accident and repair cost ended it.
Xantia Esate TD. Bought in 2006. First Citroen and bought because of the suspension and potential to run on veg oil. Apart from a stint owning a doomed C5 estate I've owned nothing but Xantia TD saloons and estates since. All have Bosch pumps so veg oil since 2006 for me.
x 3

Re: fast idle staying on when the engine is hot

Post by xantom »

Just dashed out and checked that, but no joy. Seemed like a really good possibility too because my aircon has no gas and a very dull light on the dashboard button so it could well have been on permanently without me realising. Alas, not so. Thanks though.
Tom
Tom
1998 Xantia Mk2 1.9TD Saloon
1996 Xantia 1.9TD Estate Mk1
(Previously Old Guy's)
xantom
Posts: 65
Joined: 26 Aug 2008, 14:33
Location: Near Lincoln
My Cars: Renault 16 - my first car bought secondhand in 1980. Lasted a couple of months before dreadful rust brought it to an end.
Renault 18 estate petrol. Bought in 1981. only new car I've ever owned and only because it was tax free to Forces in Germany. Lasted 18 months before accident write off.
Renault 18 saloon petrol. bought in 1988. lasted 3 years before accident and repair cost ended it.
Xantia Esate TD. Bought in 2006. First Citroen and bought because of the suspension and potential to run on veg oil. Apart from a stint owning a doomed C5 estate I've owned nothing but Xantia TD saloons and estates since. All have Bosch pumps so veg oil since 2006 for me.
x 3

Re: fast idle staying on when the engine is hot

Post by xantom »

Still not fixed the fast idle speed. I have checked the voltage to the electrovalve and at hot engine idling (still sitting in choke mode though) the voltage is about 9V. When I raise the revs a little the voltage rises to about 14V. I feel it is certainly that the electrovalve isn't getting the necessary 14V when the engine is hot, so something isn't telling it. Does anyone know which temperature sensor is the one that is being used to sense temp for the hot idling kick-in. Everything else appears to be working.
Tom
1998 Xantia Mk2 1.9TD Saloon
1996 Xantia 1.9TD Estate Mk1
(Previously Old Guy's)
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falling-out-with-my-car
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Re: fast idle staying on when the engine is hot

Post by falling-out-with-my-car »

Tom,

I had this problem for a long time with My S2 xantia but it turned out to be a tiny split in the vacumn pipes that connect
the the elctrovalves on the bulkhead inbetween the Vacumn pump on the end of the camshaft and the LHM tank.
the split was in the smallest lenght of tube and hardly visable being at the back against the bulkhead completely out of view.
I'm hedging my bets is a split vacumn pipe even a tiny split at one end will make a difference to the vacumn.
my vacumn hoses all join together with a tee junction and dont have seperate functions, one vacumn pipe from the pump to a tee. Have you undone the vacumn pump end of the vacumn pipe to see if the o-ring is worn it could be loosing pressure there.at the puump end? I have seen the replacement switches for the bulkhead new on fle-bay recently if you have to go there.
My Father however has a Mk1 VSX Xantia and occassionally the throttle cable NoN-original slips through the bulkhead which raises the engine speed slightly to a fast idle and you have to get out open the bonnet hold the throttle arm on the fuel pump closed and pull on the case of the throttle cable and the engine speed drops, it will behave for a while maybe even a few days and the casing slips back through the bulkhead again.i am wondering if you have the same issue with a non-orriginal cable. our independant is aware of this and says it is something to do with the actual bulkhead more than the cable itself I'm not sure of the detail but I can find out tommorrow and post it here.
Regards Nigel.
Citroen Xantia S2 1.9 TD estate 189K soon to be broken for parts Jan 2017 headlamps & radiator fan assembly already spoken for & A 1987 Citroen 2CV6 special just for fun.
New addition Citroen C5 2.0 HDi Exclusive Hatch purchased 09/12/2016 with 83K on the clock.
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