12 replies to this topic

[MatthewsDad]

Hi,

 

I'm new to the forum and this is my first - and seemingly stupid - question.

 

I have been trying to deal with a rich / high rev idle problem on my '95 Cooper.  I have previously replaced leaking vacuum hoses from the inlet manifold to the vapour trap and from the vapour trap to the MAP, and flushed the cooling system which was heavily corroded and full of gunk.  This made a difference, reducing the idle speed from @2000 rpm to 1500rpm, which still seems high.

 

Today I removed the inlet manifold to have a peek at the coolant temperature sensor and this is also in bad shape and has obviously been played around with in the past.

 

While everything is stripped down I was going to change the lambda sensor.  I haven't run a diagnostic but was going to replace as there's no record of it being replaced in the past and there is 100K on the clock.

 

Problem is that I can't find the lambda sensor - there is nothing around the exhaust manifold.  I have looked, honest!

 

There seems to be a sensor on the exhaust front pipe - in between the catalyst and down pipe - but no idea what this is and whether I should tinker with it.  There seems to be a lambda sensor heater relay near the inertia switch but this heads down into depths of the engine block, and I could be wrong that it's lambda-related.  Is there a chance a previous owner has fitted on a non-injection exhaust manifold?  Could an injection car function without one?

 

Any advice appreciated.

 

Simon

 

 

[spiguy]

I'm sure I remember when I tried to fit a maniflow downpipe many moons ago to my 95 SPi, that the location for the sensor on that pipe was further down than standard. On a standard setup it is in right up at the back of the head. I suspect your theory is correct. The car will run without one (although it sounds like you have one, just further down) as the ECU will substitute a value for the missing sensor (0.8V) and fuel it accordingly. The effect of this is a slightly rich mixture, but it should run fine that way - although it would fail an emissions test. The connector for the O2 sensor is to the left of the air box, near the relay pack, so you should be able to trace the wires to check they go to that sensor. It should be a 4 wire cable (2 white, one black and one grey).

Edited by carlukemini, 25 April 2015 - 09:48 PM.

[peter-b]

My Japan spec SPI, 1994 model, had sensor in the engine pipe, not in the cast part of the manifold.
It also had a cat temp warning sensor. I don't know if they sold the jap spec ones anywhere else but Japan but just thought i'd mention it. :-/

[FlyingScot]

Japanese spec lambda sensor is in the same place as UK spec on the cast manifold as described by Carlukemini, if it's elsewhere then it's an aftermarket exhaust (and can lead to issues).
Catalyst over temperature sensor is std.
FS

Edited by FlyingScot, 25 April 2015 - 10:03 PM.

[spiguy]

My current mini is a japanese one too and it also had the sensor in the 'right place' but it did have that overtemp sensor. I couldn't be bothered removing the gubbins for it when I fitted a playmini exhaust, so I just wired in a 100 Ohm resistor in place of the sensor (it is in a wee box under the carpet). The overtemp sensor is a PT100 thermocouple. Still beeps at me everytime I turn the ignition on!

 

I remember when I fitted the playmini I just cut the cable to see what would happen. Glad I left it running a while, as we were going out on the cars first club run the next day and to my surprise there was no beeping initially so I thought "great" ! A few minutes later it started beeping like mad. That would have been annoying!

Edited by carlukemini, 25 April 2015 - 10:08 PM.

[xrocketengineer]

Japanese spec lambda sensor is in the same place as UK spec on the cast manifold as described by Carlukemini, if it's elsewhere then it's an aftermarket exhaust (and can lead to issues).
Catalyst over temperature sensor is std.
FS

Yep

[MatthewsDad]

Many thanks everyone for your helpful advice!

 

I left what I believe to be the lambda sensor in the front pipe - I was running out of time to get the water sensor and manifold job done and didn't fancy opening up a potential can of worms with the lambda sensor. The lambda sensor seems to be mounted within a botched welding job on the front pipe (three white and one black wire, rather than white x 2, grey x 1 and black x 1) and I've decided to replace the front pipe and exhaust manifold (with the correct sensor point) in the near future.

 

Frustratingly the new water sensor doesn't seem to have sorted the idling problem - still rising from 1,000 rpm to 1,500 rpm very quickly when the engine is warm.  I have done as much as I can myself and will need to revert to a specialist with a diagnostic kit as I suspect an electrical fault.  Can anyone recommend a diagnostic person in the Warrington / Cheshire area?

 

 

 

 

[humph]

I had a fast idle/rich running problem. I replaced the sensor, didn't work, turns out I needed to test the wiring to the sensor.  The engine bay loom has a habit of rubbing behind the manifold, mine had rubbed through and no power was getting to the sensor, ehnce the issues. Once the loom was repaired the problem was sorted.

[MatthewsDad]

Thanks Humph I think you're right - the nature of the problem is that from a cold start up I have a stable idle speed until something kicks in (or fails to kick in) when the engine is hot.  The rise in idle revs is really quick - a second or two - and then it sits at 1,500 rpm.  I think it is something electrical not working which would otherwise help to control revs once the engine is hot.  Now I need to find a mini auto electrician....

[humph]

One guy who does know his way around Minis is Mikey at Formby car electrical. You can contact them here www.newministuff.com, don't be put off by the new mini title (if that is you're want), Mikey has been around Minis for years. Mikey repaired my loom when I had the problem. If you get it sorted by June you might want to speak to him about the Lakes weekender he organises, there's a thread on here.

Edited by humph, 27 April 2015 - 12:39 PM.

[xrocketengineer]

One more thing to try could be to disconnect and plug the red red vacuum capillary pipe that goes from the manifold to the air filter housing. It might be possible that the Thermac valve in the air filter housing snorkel has a leak when it attempts to open the warm air flapper valve. Reference Entry #9 in the thread below:

 

http://www.theminifo...oint-injection/

Edited by xrocketengineer, 27 April 2015 - 07:57 PM.

[MatthewsDad]

Thanks for the additional feedback.

I will call Formby car electrical in the morning.

Xrocketengineer - thanks for your suggestion.  I have a K&N filter so the red vacuum pipe is blanked off, but worth suggesting.

I'll keep you informed of progress.  I will get it sorted!

[MatthewsDad]

Hi, just a quick update to say that the idling problem seems to be sorted.  There are still a few occasional blips, but it is much better than it was.  Although I think there were a few separate causes of the problem, for example split vacuum tubes between inlet manifold and ECU, I'm guessing that the biggest source of the problem was a faulty coolant sensor in the inlet manifold, and the manifold being contaminated with corrosion from the ends of the coolant inlet and outlet pipe.  I flushed out the inlet manifold with a hose pipe both when I had it out of the car and again after re-fitting it.

I will probably still arrange for an ECU diagnostic in case there are any residual problems, but the coolant sensor seems to have been the main culprit.

Edited by MatthewsDad, 11 May 2015 - 09:37 PM.