CT engine....ACAV valve?

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Kitch
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CT engine....ACAV valve?

Post by Kitch »

Lets see how many others have seen this before!

Basically the Activa is showing the orange ECU light for alot of the time. It comes on when idling for a while, or if the engine is hot ie town driving.
It doesn't show when the car is cold, so first thing in the morning or on the drive home from work having been sat up for a while. But should I stop mid journey in either of these cases, turn it off for a minute then start it again the light will illuminate.

The problem with the light being on is that the fuel consumption is dreadful! It also means if I increase the boost, it will limit it while the light is on, which isn't fun.

I had the car plugged in to a diagnostic machine which said the fault was the ACAV valve. I've never heard of that, but going on the Citroen PR-net lookup it brought up the following diagram: (sorry about size)

Image

The only two related sensors there are number 15 (Idle control valve) and number 20 (Reheating unit).
The car idles fine most of the time. Very occasionally it struggles to idle when re started hot but otherwise good. If you unplug the ICV when running the revs rise and fall back into place when replugged....whether the light is on or not.
The interesting thing is that mid journey while the light was on, I stopped and unplugged the reheating thing (don't know what it actually does) and the light dissapeared! Only did it that one time however, possibly a coincedence?

But with the ICV being expensive and the reheating thing not, I took the plunge and bought a reheating unit. Plugged it in, reset boost, unplugged battery for 15mins and tried it. Light was out, but came on again later having let the car idle, which it was doing no problem.

The Citroen dealer said there is a common fault on this engine with the plastic boost pipe that goes to the ECU, but I'm not convinced yet.

Anyone else have any knowledge on this subject? Any ideas gratefully recieved!

Cheers
1991 Citroen BX 16valve

1998 Citroen Xsara 1.9TD SX

1993 Peugeot 106 XSi

1995 TVR Chimaera 400
wheeler
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Post by wheeler »

as far as i was aware only the old 16v engines could have the ACAV system
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Post by PowerLee »

wheeler wrote:as far as i was aware only the old 16v engines could have the ACAV system
Same here, Never heard of a PSA turbo lump having the AVAC system before.

I thought AVAC was the variable track inlet manifold worked by the air vacum valve thingy on the hight performance 16 valve lumps?
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Post by KevMayer »

From what I have picked up on this site and Activanet (http://s7.invisionfree.com/ActivaNet/index.php?act=idx) I believe that if you increase your boost to over 1 bar the ECU will cut the engine power. Standard boost is around 0.6 to 0.7 bar and the MAP sensor has 1 bar as the upper limit on its range. If your boost is over 1 bar you will surely get the engine light coming on and the engine power will probably be cut, if, in fact the engine doesn't cut out altogether to protect it against over pressure.

You will obviously only go up to maximum boost when putting your foot down.

Hope this helps. If not, try Activanet - loads of Activa drivers there with lots of knowledge.

cheers,
Cheers, Kev

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Used to have:- Xantia 1.9 TurboD SX. 1996 Blue & 1998 Silver Activa. + 1992 BX TZD Turbo.
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Kitch
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Post by Kitch »

Thanks for replies. Its not coming on because of too much boost....I know if I wind it out too far the ECU will cut it out at 1bar causing light to come on temporarily. But this car had this fault BEFORE boost was adjusted and is unrelated.

I think it could be idle control valve still, but I might hook it up at Citroen soon to get it checked out.
1991 Citroen BX 16valve

1998 Citroen Xsara 1.9TD SX

1993 Peugeot 106 XSi

1995 TVR Chimaera 400
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Mandrake
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Post by Mandrake »

Kitch wrote:Thanks for replies. Its not coming on because of too much boost....I know if I wind it out too far the ECU will cut it out at 1bar causing light to come on temporarily. But this car had this fault BEFORE boost was adjusted and is unrelated.
Even so you might have to temporarily put the boost back to normal to trace the problem....

Regards,
Simon
Simon

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Kitch
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Post by Kitch »

I did, two days ago :P

Might just burn it. :lol:
1991 Citroen BX 16valve

1998 Citroen Xsara 1.9TD SX

1993 Peugeot 106 XSi

1995 TVR Chimaera 400
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