C5 Limp mode issues

[Tony Quinn]

As you'll see from the Intro section, about a month ago I bought a 51 reg 2.2HDi Exclusive. The previous owner, Phil1969, had experienced some problems ( see http://www.frenchcarforum.co.uk/forum/v ... =3&t=38018" onclick="window.open(this.href);return false;) which was traced to a punctured swirl valve diaphragm. This was replaced by Phil1969 who reported back on the forum that the car was now OK. About a week or so into my ownership it stasrted to go into Liimp mode when under load at about 2,500revs.

To cut a long story short, I searched 'swirl valves', read all the relevant posts, particularly the guidance from cachaciero and bought a vacuum gauge through eBay. I found that the normal vacuum seemed to be 0.8 Bar, but dropped to 0.2 Bar between the relevant electrovalve and the swirl valve. Tracing the vac pipe wasn't easy as it goes through a sheath with two other vac pipes and vanishes out of sight to the swirl valve diaphram input. The plastic pipe adaptor/joiner was badly split. I replaced this and hooray it runs well now without the Limp mode kicking in. So a big, big thank-you to this forum without which I would doubtless have experienced a big bill from a garage without necessarily tracing the fault.

There was one odd thing. I also checked the electrovalve (EV) that is fixed on the side of the air box. I think it controls the actuator to the lower butterfly on the inlet manifold. Anyway, the input vac was 0.8 Bar when the gauge was simply connected to the vac pipe. But when the gauge was connected with a T piece to the EV, the vac dropped to 0.6 Bar. It was still 0.6 Bar when the pipe to the butterfly was removed and that outlet from the EV was capped. So there is a leak in the EV. Is this normal or indicates a fault in the valve part of the EV? Grateful for your thoughts,

Tony Q

[cachaciero]

The electro valves actually switch between the vacuum source and atmosphere.
The control signal is actually a pulse width modulated signal, the actual control pressure being proportional to the signal, so the value you will see with system connected up using a T piece tap in will be some pressure higher than the pressure from the vacuum pump, or in the case of swirl valves from the supplementary vacuum reservoir.

Hope that this helps.

cachaciero

[Tony Quinn]

Yes, I think I understand that. The car's running fine now. Many thanks. Tony Q