306 xsi emissions failed

Post by **CitroJim** » 15 Dec 2006, 16:34

As the light is on, you'll be best off trying to read the stored fault code(s). I don't know how but I'm sure someone will point you right.

I'd be temped to go firstly for the Lambda Sensor followed by the Coolant Temperature Sensor. The latter can be tested with a multimeter. They often go open-circuit which causes an incredibly rich mixture. Check its connections too as corrosion can cause it to send mis-leading information to the ECU.

macaroni · Post by **macaroni** » 16 Dec 2006, 11:34

OK, to update thread, the car seems to have a couple of problems, one simple and one more serious.

The vacuum pipe from the inlet manifold to the MAP sensor is split and leaking air and one of the cylinders is low on compression, so the head will have to come off.

Post by **CitroJim** » 16 Dec 2006, 12:41

macaroni wrote:OK, to update thread, the car seems to have a couple of problems, one simple and one more serious.

The vacuum pipe from the inlet manifold to the MAP sensor is split and leaking air and one of the cylinders is low on compression, so the head will have to come off.

The MAP sensor will be the major cause of the rich running then. What are the compressions? Do a dry and a wet compression test to determine if it is rings or valves. Maybe just a tight tappet.

macaroni · Post by **macaroni** » 16 Dec 2006, 15:54

Yes, I've fixed that. The rubber pipe connecting the vacuum tube to the MAP sensor had split. The car runs much better now.

It might be a sticking tappet, I can hear a kind of chuffing sound from the inlet manifold, as if compression is escaping from somewhere. There has been some shenanigans at number 3 pot because that plug is bigger than the others, as if it has been tapped.

I haven't done a proper compression test yet. The garage tester wouldn't fit properly, so I will have to use mine, which is currently at work.

Aren't cars fun?

Post by **CitroJim** » 16 Dec 2006, 19:18

Excellent! It might just do the MOT now. Only thing is, if you have a leaky valve, it will push the HC readings way up and they were shockingly high before.

The "chuffing" sound is a good clue to a valve not seating well. I guess it has a TU engine so good old fashioned rockers and adjustable tappets by means of spanners

Easy to both check and adjust although the rocker box can be a devil to get oil-tight sometimes

If it is an XU then things are a little more complex in the valve adjustment area!

Good work so far Macaroni and keep us posted

macaroni · Post by **macaroni** » 17 Dec 2006, 08:32

Cheers Jim,
it is an XU10 engine. I can do TU tappets in my sleep, but not attempted XU ones before.

I'll get a Haynes manual and have a go after Christmas.

Although any clues you can give me beforehand would be greatly appreciated. I doubt it is anything as simple as a mal-adjusted tappet, but I can live in hope!!

macaroni · Post by **macaroni** » 17 Dec 2006, 09:00

OK, scrap that, I've found a 205 Haynes manual and I guess the XU9 engines are the same as the XU10 engines as far as valve clearances go.

It's the old shims job, bowlocks, I miss my TU!!

Post by **CitroJim** » 17 Dec 2006, 09:38

Yep, its shims!

I've just done the job on our 205D. It had tight inlets. The job is not too bad and Haynes covers it well enough. It is time-consuming rather than difficult. I'm not sure about petrol XUs but certainly XUDs have a tendency for the clearances to close up over time and they are at their closest on a stone-cold engine.

You'll need a good set of feeler gauges that will read down to .01mm, a micrometer and a torque wrench that will go to 13 ft lb for the cam bearing caps. I have an Excel spreadsheet to help calculate the new shims required so if you want a copy, PM me.

macaroni · Post by **macaroni** » 17 Dec 2006, 11:13

Or a good garage...

macaroni · Post by **macaroni** » 17 Dec 2006, 22:08

So after a bit more investigation, it appears that number 3 spark plug has had it's threads crossed and is sitting at a different angle to the rest of the plugs. Thus, my assumption is that the washer isn't sealing the plug properly and compression is escaping slightly through the threads. The car runs too well for it to be a valve not closing.

I'll get a new plug and maybe a 2nd washer to try and seal it, failing that, some PTFE tape around the threads!!

I'll let you know...

macaroni · Post by **macaroni** » 18 Dec 2006, 22:29

OK, I covered the threads of the plug in PTFE tape, which is apparently heat-resistant up to 250C, and used a 2nd, copper, washer to seal the gap and the chuffing noise has stopped. I took it for a blast and it seemed to go OK, so I will book it in for an MOT this week and hope for the best!!

Thanks very much for all your advice and help, I hope I won't need any more.

Cheers,

Antony

Post by **CitroJim** » 18 Dec 2006, 22:46

macaroni wrote:OK, I covered the threads of the plug in PTFE tape, which is apparently heat-resistant up to 250C, and used a 2nd, copper, washer to seal the gap and the chuffing noise has stopped. I took it for a blast and it seemed to go OK, so I will book it in for an MOT this week and hope for the best!!

Thanks very much for all your advice and help, I hope I won't need any more.

Cheers,

Antony

Excellent stuff Antony! I'm not sure the PTFE tape is a long-term fix or that using two washers is good long-term but it has proved the point and fingers crossed an MOT is now just a formality...

Get the plug thread helicoiled. Many engineering firms will do it at quite reasonable cost and most will be able to do it without removing the head. They use loads of grease to catch the swarf.

Let us know how it goes and do come back for as much advice as you need

macaroni · Post by **macaroni** » 21 Dec 2006, 19:33

Well...it passed!!
So when I got the car, the guy who gave it to me claimed he'd had a quote for £400 to get it through the test.

So far, I've bought 4 plugs (£6), an air filter (£5) and a copper washer (20p).

Not bad eh?

Thanks for all your help.

Post by **CitroJim** » 22 Dec 2006, 22:17

Result