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mcrwebmaster
Administrator
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Posted: Thursday March 13th, 2008 06:52 pm |
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My car has just failed the MOT big time on emissions. Now a little background.
The car I had from new, it has done 42k. It is a single point injection, however, it has been fitted with from new a John Cooper Si plus pack. (Modified head, hi lift rockers etc....).
It has in the past proved awkward to get through on emissions but on the last two MOT's it's got through without any problems I just made sure it was nice and hot. As it is done by a local garage, they do it as soon as I bring it in and they know the car!
This year it failed big time as you can see on the attached failure notice. Incidentally the handwritten numbers are the desired readings. Since last year it has done about 2500 miles. We have replaced the rockers, exhaust manifold and lamda sensor, and exhaust system from the cat back.
Today we have replaced the plugs and put in a new airfilter and checked all the connections and the readings remains about the same. (The garage will let me take the car up and plug in the tester to see if we have made any progress with the problem.)
Our feeling is that something major(!) is not working or responding.... but we have run out of ideas! Have you any!
Thanks
Robert
Attachment: mot.jpg (Downloaded 18 times)
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64cooperS
Member
| Joined: | Saturday June 24th, 2006 |
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| Posts: | 21 |
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Posted: Thursday March 13th, 2008 08:03 pm |
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Looking at the emissions test results it would seem that you possibly have a problem with the valve seating in the cylinder head, (the hydrocarbons being very high).
The valve seats on both the valves and in the cylinder head were cut very narrow on these heads and consequently have a limited life, (especially with modern fuel).
If the head has never been removed from the engine since the conversion it would be worth taking it off and either grinding the valves in, or sending it to an engineering company for recutting.
The valve guides would be worth checking as well, as the high lift rockers and heavy valve springs put extra load on these,(if worn badly oil can find its way down the guide and increase the hc reading). If they need replacing this will need doing before the valve seats can be recut.
If you have access to a cylinder leakage tester the seal of the valves can be checked before removing the head.
The other possibility is that one of the vacuum MAP sensor pipes, (that run from the back of the manifold through a vapour trap to the ECU), has a split in the connection elbow - check these carefully as this is a common cause of poor running/emissions on the SPi.
Failing this check the coolant sensor, (under inlet manifold), and also look for air leaks on the inlet.
It is worth noting that these conversions are quite often marginal on emissions due to the high lift rockers and highly polished ports + lack of oil seals on the exhaust valve guides.
Hope this helps.
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shaddy
MCR Member
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Posted: Friday March 14th, 2008 01:58 pm |
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64cooperS wrote: The other possibility is that one of the vacuum MAP sensor pipes, (that run from the back of the manifold through a vapour trap to the ECU), has a split in the connection elbow - check these carefully as this is a common cause of poor running/emissions on the SPi.
This is certainly what caused me problems on my MOT and my car is standard.
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mcrwebmaster
Administrator
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Posted: Wednesday April 9th, 2008 05:33 pm |
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An update:
As a result of various suggestions we replaced the sensor in the inlet manifold and had it rechecked still the emissions where far to high. Lots of un burnt fuel!
I have now taken the car to someone who has the Rover T4 plug in diagnostics, which confirmed that all the sensors and the ECU are working. However, the lamda although working was reading high. With continual monitoring of the read out and increasing the revs of the engine the readings would drop to the correct readings.
All these electrics require quite a bit ommph ( technical phrase!) from the battery. Checking the output from the alternator it was barely charging the battery. A subsequent check on the battery confirmed it was hardly being charged.
Some of the earthing straps were slightly corroded these we are cleaning up/replacing to get a good earth. I have a new hi output alternator on order so with this fitted and the other work done hopefully we'll be able to get through the MOT!!
Robert
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hanlminiman
MCR Member
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Posted: Wednesday April 9th, 2008 06:12 pm |
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I hope all goes well Robert. Please let us know how you get on as this is fantastic information for injection owners.
Cliff
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hawaiianblue
Member
| Joined: | Saturday June 2nd, 2007 |
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| Posts: | 214 |
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Posted: Friday April 11th, 2008 05:56 pm |
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Giving the earth points a good clean up and check every couple of years is good for any car, even basic carb models.
Can cause poor spark. Even making the engine work harder charging the battery, causes it to run rougher.
Its not so much about the injection system needing a lot of omph more about it just not getting enough power. Petrol engines are essentially driven by electicity, so a bad earth isnt good news.
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sworks
Member
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Posted: Wednesday May 14th, 2008 06:31 pm |
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| Sounds like temp sensor which you have allready changed or a spark misfire that you have also looked at. What are your valve clearances? as tight tappet would have the same effect
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mcrwebmaster
Administrator
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Posted: Wednesday May 14th, 2008 06:55 pm |
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Thanks for that. I will have a look at that.
We have now replaced the alternator, battery and made sure the earthing points were made good. We also replaced couple of earthing straps.
A long run to the garage showed no improvement when put on the emissions test.
It has now been suggested to me that there is a regulator or pressure valve in the injection unit which can prove faulty, by sending too much fuel through. I have been promised a complete injection unit off a car which has just passed it's MOT. May be that will cure it ... but I'm not holding my breath!
Robert
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sworks
Member
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Posted: Wednesday May 14th, 2008 07:44 pm |
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| I've never known a foel regulator fail but theres always a first time. Can you remember what the oxygen sensor reading on T4 was? I assume the cat hasn't been removed/bypassed Last edited on Wednesday May 14th, 2008 07:47 pm by sworks |
mcrwebmaster
Administrator
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Posted: Wednesday May 14th, 2008 09:47 pm |
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Can't say that I can recall what the oxygen sensor reading was... the chap who did the test is quite an expert on spi engines and the test did say all sensors were working properly.
Yes it does still have the cat on!
Robert
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sworks
Member
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Posted: Thursday May 15th, 2008 06:12 pm |
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| Am i right in thinking the car runs / drives ok. If everything is working ok i wonder if the ecu is causing the over fuelling? I have a spare somewhere if you want to borrow it. You would have to get it programmed to your car using T4 then check the emissions. I also have a spi modified by JCG. i replaced my ecu at about 30,000miles as occasionally my car would either stall or tick over at around 3000 revs (would probably be ok to use to confirm or deny ecu problem)
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