Faulty idle stepper motor and high HC

[lancia58]

Hi

I found out that the idle stepper motor in my 2.0 16v Xantia is faulty. I used the Lexia to check it and after that at idle the engine stopped. The only cure was to hit the stepper motor , ( I guess it released the actuator ).The idle is still not stable but at least the engine doesn’t stop. Can a faulty idle stepper motor be the cause to a high HC ?

Thanks
Zohar

[VertVega]

Cleaning idle stepper might help. I have done it a couple of times before completely replacing with a new one.

In mine high HC was caused by the defective catalytic converter.
Structure/Material inside was in pieces and most of it was gone and mixed to the road dust

[citronut]

what i have found with suspect stepper motors,

remove them and give them a good blast with carb cleaner,
this on its own should make it work long enough to proove its at fault,

at this point i used to buy/fit a new one, but i have since found after cleaning them give them a dose of duck oil (NOT THAT W STUFF),

all of the stepper motors i have done this to have carried on working corectly,

what happens is they get jamed up with carbon which stops them opperating smoothly, then carb cleaner clears the carbon but removes any lubricant they originaly had,

regards malcolm

[Harry1975]

what does HC stand for, yes i know im being thick lol

[addo]

HydroCarbons. As in, unburnt fuel products measured as a proportion of exhaust fumes.

[Harry1975]

thanks I understand now lol

[VertVega]

It was the only time when my Xantia failed MOT due to the high HC readings
I bought a new catalytic converter and so far no problems

Lancia, How's it going with your Xantia ? Keep us informed

[lancia58]

What was the HC readings when it failed the MOT ? With my Xantia there is a smell of petrol at the muffler

Zohar

[VertVega]

What was the HC readings when it failed the MOT ? ...

That was a difficult question I had search from my archives. I found some pics and one of them shows reading ppm Vol HC value 157 with the defective catalytic converter.
The new one gave these results: ppm Vol HC at idle 5 and with the revs 11.

Petrol smell indicates the unburnt fuel which would be caused by some other source than catalytic converter. It's not good for the cat. and finally excessive heat will destroy it.

Did you check spark plugs? Is the Ignition coil working fine (if it runs on 3 you'll feel it and also hear it),
Worth checking the condition of the above.

Edit: I found this information from Bosch pages.
"To operate correctly, the catalytic converter must rise in temperature very quickly.
In effect when the temperature is below 350 ºC the catalytic converter can not process the pollutants.
The ideal temperature for efficient purification is between 600 and 800 ºC.
However too high temperature above 1000 ºC may destroy the catalytic converter."