8 replies to this topic

[bedfordbeagle]

Can anyone help please - Cooper SPI (1993) has been running beautifully for the last year. Perfect starting and happily covering a 30 mile daily comute over the last 3 months.

 

Took it in for MOT - didn’t pass emissions - high CO (they gave it 5 attempts varying the revs and noted that it was smelling slightly rich). 

Then the engine stalled and it would not restart - so the test had to be abandoned. The examiner had a quick check of the leads etc and suggested the coil could be on its way out as there was little to no spark.

 

Left the car for 20 minutes to cool and it finally started and gave me a very lumpy 4 mile drive home. Revs would die with any acceleration other than the gentlest touch. 

 

Once home put in a new coil and it is still virtually undriveable. With the engine running a small amount of fumes are floating round the engine bay. Checked the plugs and they are all black (they were were a perfect tan colour when checked the day before). Took the air filter off and on tickover what looks like far too much fuel can be seen firing from the injector.

 

The vacuum pipes all seem ok. The oil level was showing just over the maximum.

 

So what is the best way to find out what has failed?

 

[spiguy]

You say the vacuum lines all look OK, but really, the most common cause of your symptoms is a problem with the vac line which leads down to the ECU MAP sensor, and it is very hard to tell by appearance if the pipes are OK. The closest you can get to checking them really is to remove them completely and prove to yourself that they have no leaks by covering the end with a finger and creating a vacuum by sucking the other end. Even at that you need to try bending and flexing the ends whilst doing that as there can be fine cracks which won't be obvious, but once the pipe is installed the direction it is stressed in can open the cracks up.

 

The safest thing really is to replace the vac lines and the fuel trap if possible, but by all means try to find if there could be a leak in any of them using the above method. Don't forget the small one behind the inlet manifold which runs to the fuel trap - this is the most likely culprit. If you have an 3 or 4mm silicon or rubber hose lying around (even washer jet hose) you can use this in place of the vac lines for testing (Some people - me included - actually replace the long run from the fuel trap to the ECU with silicon vacuum hose..)

 

The fact that the car was fine until you took it for MOT makes me think they have disturbed something. Another option is actually that the vac line (most likely at the ECU end) maybe pushed on too far and so blocking the elbow off causing the same end result. Maybe they thought they had snagged the pipe with the bonnet stay or something and pressed it on just in case? Or maybe they have snagged it and caused a crack at the elbow / pulled the plastic hose out the elbow etc.

 

Until you have thoroughly checked or replaced the vac lines, then don't rule them out. It's almost always down to the vac lines (the ones that feed the ECU Map sensor that is).

 

As for the impression of too much fuel spraying in from the injector, it is unlikely you would be able to tell the difference between normal and rich mixture by looking at the injector. It will always look pretty much like it is spraying constantly - remember that the SPi is basically an electronic carburretor, so that single injector has to deliver all the fuel required by all 4 cylinders.

 

Other possibilites include an issue with the O2 sensor falsely telling the ECU that the car is running very lean - can happen, an easy check for that is to unplug the O2 sensor - the connector is easily accessible and sits to the left of the airbox as you look at the engine, near the black relay box. It is a 4 wire connector - 2 white, one black and one grey. If you unplug it and the car runs OK then you have either a faulty O2 sensor, or a wiring fault such as chafed insulation causing a short against something etc.

 

Another possibility is a problem with the coolant temperature reading. What is your gauge showing for a hot engine?  If it is reading falsely low, then this can cause overfuelling.  If the ECU thinks the sensor is faulty, it will ignore it and assume a hot engine condition - therefore a 'dead' sensor shouldn't really cause your issue, however one which is reading low could. Also a coolant blockage in the inlet manifold (where the sensor lives) could result in a false cold reading with the same overfuelling outcome.

Edited by spiguy, 15 September 2015 - 02:58 PM.

[bedfordbeagle]

Thanks spiguy -  a good list of things for me to check - I'll let you know how I get on.

[spiguy]

Cool. Will probably turn out to be something simple

[bedfordbeagle]

Spiguy - you’re a star!!!

 

Even though I had checked the vac lines and connectors I hadn’t removed them all. When I did, I found it: the line running from the ECU to the fuel trap was totally melted and blocked.

 

Replaced pipe and car runs OK again

 

For what its worth I did disconnect the O2 sensor and the engine still seemed to run OK. So the O2 sensor or its wiring may be faulty.

 

Now I need to sort out the emissions. The cat is only a year old. (Last year it initially failed emissions - the old cat had been bored out and no-one told me!! See this thread: http://www.theminifo...h-co-emissions/ )

 

All this leaves me with a few questions:

 

1. Should anything get so hot as to melt the vac line? (I know the MOT examiner tried several times to get the car to pass the emissions test so the car was hot - but the temp gauge stayed on the centre mark).

 

2. If this vac line was slightly melted (ie not totally blocked) could the restricted vacuum cause high CO (2.95) when HC and lambda fast idle results are OK?

 

3. If the O2 sensor or its wiring is faulty then could that cause high CO (2.95) when HC and lambda fast idle results are OK?

 

4. Could a cat fail in less than a year?

 

All help appreciated

[Alpenflitzer]

If unburned gasoline gets into the catalyst and may be partially be burned there, you get an "eutecticum", i.e. that the platinum-rohodium catalytic coating lost its efficiency to catalyze..Therefore it could happen, that after a short time a cat fail.

My SPI once ran very rich: Cleaned the gas trap, replaced all of these fragile vac tubes with silicon tubes from Samco (inner dia 3 mm). These silicon tubes are simply being stuck on the littel valves without any black of these black angular plastic-ends. They are flexible and there are many colors available.

And, I had to buy a new catalytic converter.

[spiguy]

Good stuff bedfordbeagle, getting there now. You said that it was the pipe from the ECU to the fuel trap that was 'melted' ? Just want to confirm that you do indeed mean the long pipe from the ECU box on the inner wing up to the fuel trap, and not the short pipe from the fuel trap to the inlet manifold?

 

I have personally had the short pipe 'melt', and as it turned out the reason for this was that I was using a generic bit of plastic vacuum pipe. It had basically gone soft and folded in on itself.  It would seem that the proper Rover vac lines are made of sturdier stuff, and can cope with heat better. But as I say, that was the short one behind the manifold, which will see more heat due to it's location.

 

So, questions - is the pipe which melted the proper Rover pipe or is it a replacement pipe of unknown source?  the original pipe should look like this :

 

http://www.minispare...cuum pipe.aspx|

 

 

You said you replaced the pipe, did you use the above pipe - ie the proper Rover one?  How are you routing the pipe?  I can only guess that the one which melted may have been routed such that it was lying against the engine block / cylinder head / metal bit that heats the underside of the air box. That could explain why it softened / melted. The pipe should be routed like a diagonal line from fuel trap to ECU, away from 'hot bits'.

 

Regarding disconnecting the O2 sensor, don't worry - you won't notice any difference in the car's running when disconnected. The ECU assumes a value in the absence of the O2 sensor signal, and can run very well without it (doesn't mean you don't need it though!) so the fact that you saw no difference in running with it unplugged is perfectly normal and not cause for concern.

 

I think that the whole saga has likely  purely been down to the melted vac line. It probably softened and collapsed, so then the MAP sensor in the ECU saw no vacuum. If the car seems to be running fine now having replaced that line, I think your best course of action is to take the car to the MOT station and have them check the emissions. If they are OK now, then just get the retest done. I only suggest that because you only get 1 free retest.

 

My local garage will test my emissions for a fiver, so you should hopefully be able to do the same. I'm assuming of course that your current MOT is not expired.

 

If you find you still have emissions problems, then is the time to start worrying about the CAT etc.

[bedfordbeagle]

Thanks again spiguy.

 

Yes it was the long pipe from ECU to fuel trap and it was almost certainly an aftermarket pipe - probably 6 inches longer than the original. Perhaps being long a loop of pipe to come into contact with "a hot part".

 

I've replaced it with generic vac pipe for the time being - but have been careful with the routing.

 

Will follow your suggested course of action and report back.

[brivinci]

So, you can confirm that a 3mm (1/8th") ID is what you want to order for the silicone hoses to replace the vac lines? I have a set on my car that my mini supplier here sent me. I want to buy a set for my brothers car now.