16 replies to this topic

[AlexM]

Ive just dropped off my mini at my local specialist MiniFarm, so I'm just waiting to find out what sort of problem it has :'( I'm hoping it doesn't cost me too much, but my money is on it being something like the stepper motor or pedal sensor, or maybe the noisy valve gear.

[AlexM]

Got my mini back the air temp sensor was detecting a fault and the idle and throttle was adjusted. So it now runs much better Yay!

[Sprocket]

Good to hear

[AlexM]

My previous joy is curbed somewhat as my car ran really badly from cold this morning and the idle still varies and the car backfires on overrun.
The guy who worked on my car says that he "removed the fault from the ECU" but this could mean that it will just come back again if the sensor was at fault in the first place.
I told him that I wanted a diagnostic printout, but he didn't give me one and just said that everything was as it should be with the car, so I didn't persue it as I was glad to have my car back, i don't think he did the diagnostic at all, and I specifically wanted to know the sensor readings so I could choose to replace any that were reading out of bounds.
The idle stays at or around 850rpm and varies about 50rpm each way but doesn't have a regular pattern and my vacuum gauge needle does a similar thing. I have been in another spi and it ran totally smooth. I think the problem must be related somehow to idle control so it must be something like the stepper motor or Throttle position sensor.
Is there anyway to find out if the stepper motor is working correctly? Should it be constantly making adjustmests while the car is running as I don't see it moving around when the engine is running or as soon as the ignition key is turned. Does it operate the throttle linkage as if you were moving the pedal or is its movement contained within the injector housing?

Could everything return to normal after a few hundred miles driving?

Sorry for all the questions, I find this all very frustrating, I prefer doing things myself but I don't have a diagnostic machine.

[Sprocket]

What is going on is the ignition advance is fuctuating and in doing so the engine speed is also fluctuating, this will then cause the stepper to also fluctuate to try and control the idle speed to 850rpm. One fights the other and hence an unsteady idle. Check that there is no liquid in the vac line to the ECU (I know you have already). Ensure the throttle cable is properly indexed and where possible reset the ECU ( Best suggested method - remove the electrical connector from the ECU over night)

There are no faults to clear on the SPI ECU so that is bolox. Either the sensor works or it doesnt the diagnostic just tells you that, its live information not logged, there are no logged faults what so ever.

There are specific tuning tasks that can only be done with the diagnostic and need to be done to correctly tune the stepper position at idle and also idle speed.

I realy would advise if you are considering keeping the SPI for a considerable time to buy one of the Crypton ACT diagnostics, they are not that expensive, relatively speaking, at around £50 on ebay

http://cgi.ebay.co.u...1QQcmdZViewItem

I'd actualy be suspect about this being able to comunicate with MPI, I think its a mis print and should be SPI, but I may well be wrong, interesting if it does though

[icklemini]

good lord

wether its an SPi or MPi its still a MEMS system. Fault codes (albeit a bit pants on MEMS) are logged.


Having done quiet a bit of diag work (not just minis) i can honestly say its *more* than just plugging in a FCR to get a fault code - its back to basics stuff with multimeters and stuff to actually find the cause by testing sensors, etc.

Often if a fault is logged on such and such sensor that sensor is replaced. Often its not that sensor though thats at fault...

[AlexM]

A diagnostic tool will be able to detect which sensors are at fault though wont it? And a fault code reader will simply say whether or not all sensors are operational, not whther or not they are wearing or reading poorly?

I wanted thye diagnostic test and the printout so I would know which sensors are reading poorly and replace them.

I didn't realise that these tools were as inexpensive as this, I always thought they would be around the £500 mark. But if i can get one for around £50-60 then I would definately consider it, especially as i plan to keep hold of my car for a while and i know a few other people with spi mini's that have experienced problems.

I drove home today as smoothly as i could. The idle remains quite random over a small range of revs and the accelerator pedal seems to randomly becomes light and heavy which is rather strange, most notably light when i first start the car, this is what makes me think its an throttle control problem. It makes it quite difficult to control the engine revs when pulling away, and i stalled unexpectedly yesterday as the throttle went solid and did a big wheelspin from a junction as the throttle suddenly went light and the revs shot up. When holding the engine at speed under load the vacuum reading on my vacuum gauge fluctuates like it would at idle, in the same way as the rev counter does.

I do have a multimeter, so how would I go about testing sensors with it? Would I need to read to certain values? I have only ever used it to check my alternator was charging. Could something like a stepper motor stiffen up over time and just need some oiling?

(There is some good coming out of this as it is all relevant to my college course)

[Sprocket]

The trottle cable might be getting stiff and due for a change, there is very little spring pressure on the throttle body and some times there is not enough pressure to return the trottle completely with a stiff cable so the stepper wont actualy be contacting the lost motion link, hence maybe an other reason why the idle is fluctuating. Still think the Stepper needs tuning by the sounds of it, more so if the cable is actualy stiff

What you describe is a symptom of stiff cable but I havent seen it and can only speculate.

Hope you get to the bottom of it soon

[AlexM]

yeh me 2, i jus want the car to run as it should, nothing fancy, lol. I will get to the bottom of it! I definately let u know what it turns out to be. Cheers for the help

[THedooBZ]

hmm nwo if that diagnostic tool worked for mpi's that would be worth the investment.

[icklemini]

A diagnostic tool will be able to detect which sensors are at fault though wont it?

And a fault code reader will simply say whether or not all sensors are operational, not whther or not they are wearing or reading poorly?

a diag tool can be anything from a multimeter through to a scope through to a FCR with certain functionality built in.

often a sensor will log a fault and its assumed the sensor is at fault - it may not be as its just that the sensor has *detected* the fault - this is then why you have to diagnose the sub-system based upon the information presented to you.

For example:
A lambda sensor 'running lean' and (maybe) logging a fault (or other symptoms like excessive fuel consumption..) can be down to an air leak at the manifold.
Measuring the output of the lambda sensor using a multimeter will show you the voltages as it goes high and low..
Using a scope will show you the waveform (which should be a sinewave)..
Measuring it at the sensor would prove the sensor - measuring it at the ecu would prove the wiring as well to the sensor..

Another example (on a ford galaxy)
What was a faulty lambda sensor (logged as being 'out of range'), caused 2 other fault codes to be logged - all to do with the exhaust gas recurculatory gubbins. As these are all connected in the subsystem of 'exhaust'. The lambda was proved to be at fault and replaced. The EGR gubbins was left untouched and have since not logged a fault. - Basically as the lambda was playing up, the ECU shut off other things associated with the exhaust system.. Moral here is again dont jump in and replace as it can get quite expensive!!

Another problem recently turned out to be faulty earth on the ECU - the problem with the car and the error code logged was *nothing* to do with the actual fault or the remedy - Moral here: Check the obvious - including the mechanical things (like throttle cables!)

A FCR isnt the be all and end all - its just another tool, how well you use it is the key.

TTFN,
Dave

[AlexM]

Right, I have another update on this.

*breates in*

Returned to the specialist and he assured me that he had done the proper test before using a crypton diagnostic tool, and that all the sensors were reading well within the correct parameters. The fault was logged because because of proplems I previously experienced with a hole in the vac line to the ECU which caused havoc with everything.

He says that a vac leak is the only other explanation to the erratic idle and judder when pulling away as well as the higher fuel consumption. I have checked the vacuum lines and the MAP sensor fuel trap to be sure of no fuel in these lines and they are all clear.

A while ago I enquired about the purge control valve wiring connector on the right side of the engine bay, and that I never had a plug for it, so this was not functional. He told me that he noticed this was missing when I returned yesterday and explaned that it can cause running problems.

link

At the time I posted this but never read the reply and forgot about it. I have been told that this is important to the fuel pressure and emmissions control within the tank and inlet manifold. I was told it is now illegal to vent a fuel tank to atmosphere in the fashion of old cars due to present emmissions laws, in order to compensate for this a charcoal canister is places under the left hand wing which collects the excess from the tank and also the inlet manifold. This vents after you have been driving a while and releases any pressure in the inlet manifold into this canister. If this does not function the vacuum reading in the inlet will suffer and could cause running problems and and backfiring because the vacuum in the inlet is replaced by added pressure .

This is simply interpretation of what he told me and it does kinda make sense and would explan a few things!

So, I need to get this wiring connector and find out where the air leak in my inlet is coming from if I want to solve my running problems. The purge valve wiring connector is different on the mini to other rovers i have seen as I tried recently to get one from a breakers yard but only found a different type on the rover 25's 200's and metro's that were there, so i will be going to the local electrical supplier to find this part.

I also need to know where other possible air leaks could be occuring around the inlet. I can hear air escaping around the inlet but very faintly and I made huge care to seal this (although I didn't use any gasket sealant or paste at the time) and have fitted another exhasut manifold to another user of this forum and we experienced no idle problems as a result and we didn't use any paste on his exhaust either. I will remove the throttle body this weekend and seal the spacer between the inlet and the throttle body to esure it isn't that which is leaking. I will be getting the wiring connector before I do this incase it is merely a symptom of this being missing.

Will dissconnecting the battery be enough when working on the Injection system? Or are there further precautions I should take to making sure that it works as it should when I start the car again I don't want the system to log another fault and cause even more problems.

[Jammy]

You gonna breathe out now??

[Sprocket]

The only thing I will say about that is, If the connector is missing and the solenoid is not connected to the ECU, the valve will be closed and manifold vacuum will be unaffected and fuel pressure is regulated buy the regulator in the injection housing, returning excess fuel to the tank. What may happen is tank pressure would rise. The canister does not collect anything from the manifold.

I smell some bull mixed in with fact so that it wouldnt be obvious, but then the bloke may well believe it himself, dunno.

As for the connector, i have one you can have off an old loom ( it'll be the only one that wont get used off the loom), you'll just need to splice the wires together. You are welcome to the valve as well if you want.

And again I will say that the injection system needs a proper tune, not just resetting. Are you going to Drag Wars by any chance??

PM me any way

[m3ntalist]

I had similar problems to this, but a mobile crypton bloke came round today. It idles much better now and is nice and driveable. He said the throttle linkage or the whole spi system may need replacing in time as its quite old now ~10 years.