12 replies to this topic

[roblightbody]

Hi there,

My 94 Cooper won't warm up for whatever reason. The dash temp gauge never rises above 1/3rd, whereas it used to go to just a fraction under halfway, which I remember my then-new classic Minis doing in the 90s. Other symptoms are an almost permanently high idle, although occasionally it does idle correctly and the fact that it destroyed a new catalyst (going to IMM and back!) because I think it was running rich the whole time.

I've checked/fixed the vacuum pipes/elbows and all's well. I even checked the flap on the air filter box was working when cold, and it is. My excellent mechanic flushed the cooling system, and replaced the thermostat - twice.

So now I've bought an ACR2 to test it with. Can someone advise what the following readings might be telling me please!?

All tests - clear - no error codes.
From a cold start (after 2 weeks of standing outside in a Scottish Winter!) the following readings were noted.

• Ambient temp - 200C
• Batt Voltage - 13.5C
• Throttle Pot 1.80V varying 1.86V and 2.00V
• O2 sens volts varying slowly between 1.8V and 1.9V
• Engine speed 1233rpm
• MAP sensor 049 KPa
• Coolant temp - 2C rising to 31C in a few minutes, before I stopped the test.
• Inlet air temp 12C - which sounded reasonable.

From that lot, and from reading other posts on here, I think I may have a faulty lambda sensor?

Tomorrow I'm going to take it for a proper run, get it hot, then take the readings again.

Thanks for any tips and advice!!

Cheers,

- Rob

[FlyingScot]

Best to get it hot. Read the coolant temp from the ACR and compare with whether the thermostat is open (rad getting hot).
Could be faulty temp sensor and this is used by the ECU to control fuellng.
Throttle pot on my SPi reads 0.54 when at idle but not sure how this compares with cooper seems very high I.e. possible issue.
O2 sensor best tested when hot and should change quickly up and down as it corrects, slow changes implies it is dirty/on the way out.
Does the MAP change from ~100 when ignition turned to the figure quoted?

[xrocketengineer]

You probably have the water lines in the intake manifold where the temperature sensor is clogged up. You can try flushing them. See here:

http://www.theminifo...nder-on-an-spi/

[roblightbody]

Hi again,

Thanks for the replies! Got the engine as hot as I could tonight (and enjoyed myself doing it!!)

From reading everything, I'm certain the lambda sensor is faulty - its stuck at 1.8V/1.9V when the engine is running. Apparently it should be more like 0.5 and adjusting constantly. With engine off, it says 0.8V and even that's high!

Coolant sensor rises from 2C to 65C then no higher. Radiator is warm then hot almost immediately. Should the radiator stay cold until temp is away up to the 80s C? It has an 88C thermostat, like it should have.. Inside the car the temp gauge is about a third of the way up. My hunch is that the temp sensor is working correctly and the low temp is a symptom of something else... From what I've read on here, a failed coolant sensor usually tends to lock to 59C?

MAP is showing 101 with the engine not running, 044 running. Throttle Pot was 2.16V not running, 2.04V running.

Thanks for any more help and tips. I will probably ask my mechanic to swap the lamda and coolant sensors, and to check the thermostat again.

Cheers,

- Rob

[FlyingScot]

Hi Rob
Based on what you have found 1) Lambda sensor not functioning correctly, should be swing up and down within a second on the ACR.
2) MAP responding to vacuum which is good. 3) Throttle pot still seems high IMO 4) Temp behaviour wrong, car should heat up and rad stay cold until it opens at 88 degrees. If car isn't getting hot and rad warming before this thermostat system not functioning. I know you said that stat has been replaced twice but something amiss here. Does car have sandwich plate at thermostat location? And if so has thermostat been put in to the "alloy sandwich" rather than the cylinder head space?
The reference to the 59 degrees is part of the limp home built into the ECU, this is the temp it picks if something a miss (if I am remembering right) but temp won't rise up rather just show constant.
Any way you can (safely) measure the coolant temp in the radiator as the temperature sensor in this car will be tricky as it is right under the manifold as described in the post by xrocketengineer.

Edited by FlyingScot, 19 February 2013 - 04:42 PM.

[roblightbody]

Thanks FS. I think you're right about the thermostat - it just doesn't seem to be working. It could actually be the cause of the lambda failing, if the car was constantly running rich... I took it to work and back today (including motorway) and the temp gauge only just went above blue.

I was thinking of getting an infra-red thermometer... saw an RAC man using one once and it looked like just the thing!

I don't really understand what the "throttle pot" is, and what that number is telling me...?!

[FlyingScot]

The "throttle pot" is the throttle position sensor; basically a variable resistor which tells the ECU how much the accelerator is depressed.
It runs from about 0.5V at idle to 5V at fully open throttle. The number you have suggests that the position is about half way and the engine is not at idle; this seems consistent with your initial comment about high revs.
I would check that the cable is set right (has it been adjusted ?)
There are good posts on here by people with more experience than me, I suggest you have a look at the pinned posts by Sprocket there is one on setting up the cable.
If the thermostat isn't working it would cause the system to run rich, which will kill the lamba sensor over time.

[icklemini]

Engine not running hot enough so the system is running 'on choke' hence the rich running....

Needs to be 80degs at least, half way on the gauge...

so either:
a) engine is getting hot... but the temp sender isnt recording the correct value due to either a blockage in the pipework to/from the sender or a sender fault.

b) engine not getting hot..... dodgy thermostat?

Dont bother with lambda sensors yet... quite simply at the moment the system is reporting a 'cold' engine and fueling it accordingly...

[roblightbody]

Thanks again everybody. Its going into the garage next weekend for service/MOT and to fix this problem. I'll get it running hot, then attend to the lambda and throttle pot problems if necessary.

[roblightbody]

A wee update, now that my car is at the garage.

Throttle pot had failed. Hence the high reading. Being replaced. Car thought the throttle was always open. Dramatic reduction in emissions apparently when this was replaced .... also one elbow had failed (even though I checked them!).

Also the PTC heater isn't working, but may have to wait until next time. Also advised that my maniflow LCB isn't ideal, as the lambda sensor is only 'reading' half the engine...

Final question - what fan did the spi mini come with? Minispares website not making this clear to me...

[FlyingScot]

Hi Rob
Thanks for letting us know, helps build the knowledge. With my SPi I had so much trouble with the elbows and pipes, I just replaced them all with new and the fuel trap.
What fan do you mean? The plastic blade on the water pump or the electric one under the N/S wing or the interior one?

FlyingScot

[roblightbody]

Hullo again,

Car going like a DREAM! Unbelievable. Warming up to normal. Great fuel economy. Doesn't stink. Cat back on. Much, much smoother to drive, including immediately from cold (even with a failed PTC heater). Still got to an indicated 100 on an, err, disused airfield or something.

Having owned one of these in the 90s when it was brand new helps (although it was a sprite spi) I think, I can tell when its right and it bugs the hell out of me when its not!

Throttle pot was replaced which I think was the main thing. A vacuum elbow had split that I hadn't noticed. The fan I'm referring to is the main mechanical radiator fan. He says the workshop number part number was different for the cars with the electric fan - it looks the same unless you look at it closely, and see the blades are smaller and it pushes less air.

[roblightbody]

Hello,

 

Thought I'd add to this topic, a few months on.

 

Car still running perfectly, although I have a question - how hot is too hot?  See my 2 minute YouTube video where I run through the diagnostic tests on the ACR2, and it shows the coolant at 109C before the electric fan comes to stop it going any higher than that.  Is that normal?  I think the video might be helpful for the other readings, which I now think are correct - lambda sensor especially, given everybody seems to struggle with it.

 

 

Cheers,

 

- Rob