Help - MOT failure due to emissions

[prm]

The first point I would check is the MOT tester equipment with a reading that high, especially if its running fine. That is a high reading.
As previous recommendations – temp sensor.
Temp sensor reading should be ?? approx

0deg.C 5.0- 6.5 komhs
20deg.C -2.2-3.0 khoms
40degC 1.0-1.5kohms
80deg.C 250-400 ohms
Most of the GTI and 16v ECU air and water temp sensors should fall within the above ranges
The only other possible point, one or two of the injectors are leaking by.

[MULLEY]

Found this, not sure if its what u r after?

http://cgi.ebay.co.uk/Citroen-BX-Air-Fl ... dZViewItem

[Brian King]

I went down to the MOT station to beg for more time and mentioned to him that I had another Jetronic box in the shed. He said swop them over and let's put the analyser on it again, nothing to lose. So that's what I did, cleaning everything including the SCART plug and socket. Connected it all up, pushed and pulled the plug a few times, and the car started first time. Warmed it up and took it down to the MOT station and hey presto, 3.5. He wrote me out the MOT on the spot. It could be that the spare Jetronic box I had was good and the one on the car was bad, but I have a strong suspicion that one of the tags on the SCART plug or socket may have not had a good connection, and putting the plug in and pulling it out several times might have cleaned the blades and sockets. I shall put the old jetronic box on again and have him put the analyser on once more. If it shows 3.5 or thereabouts, it's almost certain to be the SCART connection that was playing up. I'll report on the result.

I've still got a dud vacuum unit on the dizzy and I'm going to phone Independent Ignition Supplies of Bideford and Express Autoparts of Kettering to see if they do one separately. Otherwise I'll be looking for a S/H dizzy. There is one school of thought I've come across that says the vacuum unit doesn't do much and you can do without it !!

[st gilles]

[mountainmanUK]

That's yet another BX got a ticket recently!!!

Well done!

[DavidRutherford]

There is one school of thought I've come across that says the vacuum unit doesn't do much and you can do without it !!

In terms of the engine running well, and producing full power, yes, the vacuum advance does very little. What it does do is provide proper economy when running at anything less than foot-to-the-floor. When you have vacuum in the inlet manifold, the engine is running at a reduced volumetric efficiency, and so increasing the ignition advance will provide increased efficiency.

Thus, you set up the engine with no vacuum advance (just dynamic advance) and get it running correctly, and then add vacuum advance afterwards.

[Brian King]

Thanks David. That is the very first time this has ever been explained to me in a way that I understand. Are you an engineer by any chance?

[docchevron]

He is, but he doesn't like to mention it!