20 replies to this topic

[MSmiley89]

Hi All,

 

Please may any of you offer some help diagnosing my problem?

 

Really sorry that this is another duplicated thread. I've read multiple over the months but not being fully up to speed on engine parts/function I may not be putting two and two together.

 

I'll give you a chronology of how it has behaved and everything that I have tried.

 

• 2016. Failed MOT on emissions. Replaced catalytic converter. Passes MOT. Given back to me and the exhaust acoustics are much louder. On the way home the car cuts out. Find that a vacuum hose has split. Mechanic replaces vacuum hose. Runs OK but still a bit rich.
• Runs OK but loses power at about 2000-2500rpm (particularly going up hill or when carrying a passenger). Then starts cutting out again.
• Take it to different mechanic. 02 sensor and another split hose connector replaced. Put on rolling road - no issues.
• Days before its MOT cuts out on a steep hill whilst stuck in traffic on a hot summer day. Towed home. Fires up but chases idle (exhaust acoustics sound like a revving tank)
• 2017. Failed MOT on emissions. Replaced catalytic converter. Throttle body cleaned and new hose connector replaced on the MAP sensor which had split. Passes MOT and runs beautifully.
• After a few drives the acoustics start to increase again. I find that the new MAP sensor hose connector (straight design) has been slipping off so I replace with an right-angled connector which offers a tighter grip. This helps but still can't find idle, then cuts out after I fire it up, then doesn't start full stop.
• It is now back at the mechanics where the following has been done: 1) New temp gauge and sender, 2) Crank shaft sensor replaced, 3) mechanic says that when he electronically loops out the SPi part of the ECU (excuse me if this is factually incorrect/not possible) it runs better but still not great. He says it will then stall after 5 minutes or so.
• Mechanic has now drawn a blank - he thinks the electronic positioning sensor/signal might be the cause but before he spends more of my money wanted to make sure he's not following an expensive train of thought.

Other info (when I last plugged a code reader in although since then the temperature gauge & sender & crank shaft sensor have been replaced)

• Idle switch Off
• P/N switch On
• MAP Sensor 39kPa
• Coolant temp 33deg C
• Inlet air temp 20deg C
• Ambient air temp 200deg C (I've read other threads and this is a 'forced' value?)
• Throttle pot volts 0.84v
• Lambda 740mV
• RPM 1211

I also should mention that the heater stopped working a while back. Could the water pump be contributing to my problems? Also wondering if the stepper motor could be faulty?

 

 

Appreciate you taking the time to read the above! Any help will be hugely appreciated.

 

Thanks very much.

Matt

[cian]

The throttle position sensor voltage seems high at idle aswell as your idle revs, has the stepper ever been adjusted

[Archived1]

Flush the coolant system and fit a new water pump. Make sure all water pipes are hooked up to the inlet manifold and use a high quality water temp sender unit.

Replace all vac hoses from the manifold to the map and through to the ecu with flexible hose. Pearly wotnots do a good hose kit.

It could be an intermittent fault with the injection unit. Theres a stepper motor in the housing thats feeding information alongside potentiometer values to help regulate fuelling and idle (ignoring lost motion settings for a while).

[attachment=193755:E17097A8-D90D-4059-AD01-EB017D645A8E.jpeg]

These are regularly causing issues like youve mentioned as they are all getting a little long in the tooth. Full throttle position and erratic/inconsistent signal can cause the ecu to lose its position memory (explaining your hill issue)

This is my own way of explaining the issue and I have fixed loads like this. Im sure someone with a better grasp on technicality with the single point injection mini will be along soon.

For now Im ignoring loose or shifted timing position rings on warm flywheels etc and iffy electrical connections. Im just giving pointers.
The stepper motor is something I bin out for a new one on all spi minis that I own nowadays. They can be bought cheaply by the part number as used in many different applications.

Edited by Elf is a mini, 24 February 2018 - 07:39 PM.

[genpop]

• Other info (when I last plugged a code reader in although since then the temperature gauge & sender & crank shaft sensor have been replaced)

  • Idle switch Off
  • P/N switch On
  • MAP Sensor 39kPa
  • Coolant temp 33deg C
  • Inlet air temp 20deg C
  • Ambient air temp 200deg C (I've read other threads and this is a 'forced' value?)
  • Throttle pot volts 0.84v
  • Lambda 740mV
  • RPM 1211

   

   

Which temperature sensors have been changed and how long was the car running when you  made these readings?

 

Imortant is the Coolant temp sensor underneath the intake manifold. A warm engine (with a good thermostat) should read coolant temp over 75 degrees.

[MSmiley89]

The throttle position sensor voltage seems high at idle aswell as your idle revs, has the stepper ever been adjusted

I don't believe so. Not since I have owned it. The readings were taken when it couldn't find a steady idle mind. A touch of white smoke was coming out the back at the time

Edited by MSmiley89, 25 February 2018 - 10:15 PM.

[MSmiley89]

Flush the coolant system and fit a new water pump. Make sure all water pipes are hooked up to the inlet manifold and use a high quality water temp sender unit.

Replace all vac hoses from the manifold to the map and through to the ecu with flexible hose. Pearly wotnots do a good hose kit.

It could be an intermittent fault with the injection unit. Theres a stepper motor in the housing thats feeding information alongside potentiometer values to help regulate fuelling and idle (ignoring lost motion settings for a while).

E17097A8-D90D-4059-AD01-EB017D645A8E.jpeg

These are regularly causing issues like youve mentioned as they are all getting a little long in the tooth. Full throttle position and erratic/inconsistent signal can cause the ecu to lose its position memory (explaining your hill issue)

This is my own way of explaining the issue and I have fixed loads like this. Im sure someone with a better grasp on technicality with the single point injection mini will be along soon.

For now Im ignoring loose or shifted timing position rings on warm flywheels etc and iffy electrical connections. Im just giving pointers.
The stepper motor is something I bin out for a new one on all spi minis that I own nowadays. They can be bought cheaply by the part number as used in many different applications.

Thanks Elf. Seems the stepper motor is the next port of call as with the coolant system. I'll give it a go

[MSmiley89]

• Other info (when I last plugged a code reader in although since then the temperature gauge & sender & crank shaft sensor have been replaced)
  

• Idle switch Off
• P/N switch On
• MAP Sensor 39kPa
• Coolant temp 33deg C
• Inlet air temp 20deg C
• Ambient air temp 200deg C (I've read other threads and this is a 'forced' value?)
• Throttle pot volts 0.84v
• Lambda 740mV
• RPM 1211

 

 
Which temperature sensors have been changed and how long was the car running when you  made these readings?
 
Imortant is the Coolant temp sensor underneath the intake manifold. A warm engine (with a good thermostat) should read coolant temp over 75 degrees.</p>


I replaced the ambient air temp sensor and now the coolant temperature sensor and sender. I think it had been running for about 5 minutes when I took those readings (I remember a grumpy neighbour complaining about it!).

Any thoughts as to what this might mean?

Really appreciate your help Genhop. Thank you!

Edited by MSmiley89, 25 February 2018 - 10:16 PM.

[FlyingScot]

Start with the basics.... service the car inc fuel filter. Replace all vacuum pipes and fuel trap as these are service items too.
This will give you a base line to work from, all the rest are frankly guesses which you don’t need.
The injection unit is generally robust, so seek out someone close to you who can lend a code reader (see pinned thread on this) as it will save trying everything.

FS

[genpop]

I replaced the ambient air temp sensor and now the coolant temperature sensor and sender.

 

coolant temp sensor  is "one thing", it is the sender .So, are you shure you replaced the right thing? It's a bit of work

[MSmiley89]

I replaced the ambient air temp sensor and now the coolant temperature sensor and sender.
 

coolant temp sensor  is "one thing", it is the sender .So, are you shure you replaced the right thing? It's a bit of work

My mechanic did and he wasn't happy about it! (So I am assuming it was a big job!)

[brivinci]

Throwing money/parts at a car is not an ideal way to try and sort it, especially these cars. As above, you need to find someone that knows these cars specifically or it will just be guess work. Do all the basic, routine stuff. Assure that you replaced the coolant temp SENSOR (under the intake manifold) and that the correct thermostat is being used. The injection cars need their own specific one, rated at 88c. I would also replace all your vac lines with silicone ones as discussed on many other threads. Replace the fuel filter. Just do all these simple things so you can eliminate them and not have to worry. Then, get the car hooked up to a scanner and start looking into the numbers. There are just too many variables with these cars. You could end up replacing everything...and then find it was a poor ground wire. 

[MSmiley89]

So, no progress since my last post. Most of the basics have been done but the more I think about it the more I think the ECU couldn't figure out the engine temperature and adjust the air-fuel mix properly.

We're are trying to source a stepper motor. Does anyone know a good supplier for a stepper motor for a 1995 SPi?

Cheers,
Matt

[genpop]

Read this thread:http://www.theminifo...g/#entry3527834

or have a look for a complete cable.Then download this software:mems-rosco.rar  from github.com/leopoldg unpack it to a laptop and check values of your mini ecu.

There is memsanalyzer from rmrsoft.com by which you may read the logfile taken with mems-rosco.

[cian]

I have a used stepper but couldnt stand over if its going to sort you out or not

[spiguy]

There's alot of information there... to be honest there's two things that struck me when reading it  - one is, what year is the car. I ask because if it is an early SPi (92 / 93 if I recall), then it will have a throttle pedal switch. If this switch fails in the closed position then the car will not want to rev above 2k - 2.5k. It can also backfire in this situation.  If you do have a throttle pedal switch then it is easy to test if it is faulty by just disconnecting it (connector is mounted in the pedal bay area). The car may idle a little high but otherwise will run fine with this disconnected (it would also fail an emissions test). My current mini had a shorted throttle pedal switch when I went to view it! (92 cooper).

 

The other thing is that there seems to have been several occasions when vacuum lines were replaced.  Do you know if these were replaced with the genuine rover parts or with general purpose plastic vacuum line?  Also do you know if it has just been the long run from the fuel trap to the MAP sensor, or the short pipe from the inlet to the fuel trap?

 

I have experienced using general purpose vac line and found that it isn't up to the heat that is at the back of the engine and so for the short pipe at least, is not suitable. I have had a short pipe collapse because it was softened by the heat to the point that it was almost closed over, with running problems following. 

 

In any case it is very easy to push the pipes on too far or misdiagnose these pipes, so if there is any doubt that these pipes may not be the correct type,  I would suggest that you buy a set from minispares (MLH10022 and MLH10026)  and probably a fuel trap too (NPC10001).

 

As regards the stepper motor, it's only job really is to provide mechanical input to the throttle in order to provide some more control over idle speed - for the most part the ECU tries to manage idle speed by altering the timing, however in some cases this is not sufficient and also in cases of low battery / high electrical load, it can use the stepper motor to literally push the throttle and raise the revs. This is done by means of a pin which moves in and out of the stepper motor body and pushes on the throtlle linkage. These fail due to dry solder joints and the like. Likely failure modes can include it shoving the throttle enough that the car revs very highly or 'drives itself' to a degree i.e. 'pin comes out too far' ( been there!) or alternatively it can fail such that it doesn't provide any idle control and the car can stall i.e. 'pin does not come out' or it can be erratic. Once you are driving and up into the rev range with a reasonable amount of throttle applied via your right foot it won't affect the car at all. 

 

Some other points - a bad O2 sensor can cause alot of issues however that said the car will run perfectly well with it disconnected. If you want to eliminate it, disconnect it. Takes 2 seconds. A bad crank sensor will invariably cause the engine not to run at all. The ECU will not provide power to the fuel pump or the ignition coil if it does not see pulses from the crank sensor. I am not sure if people have experienced intermittent failure that would result in bad running, it seems unlikely to me though.  I don't think the inlet air temperature sensor can really cause any major issues, it's value is only a relatively small part of the overall fuelling map adjustment.  The throttle potentiometer can cause issues, this is usually due to wear of the resistive track - usually in the area most commonly used i.e. from idle to about half throttle. In checking the throttle pot the best thing to do is get a meter on the output pins (middle to either outside pin will do) and slowly operate the throttle whilst watching the reading. It should increase or decrease (depending on which outer pin you are using) steadily with no spikes in value and at no point should it go open circuit. Usually a dodgy throttle pot will get to a point in the track where it either jumps in value or goes open due to a break.

 

I was baffled by your mechanics comment '" mechanic says that when he electronically loops out the SPi part of the ECU (excuse me if this is factually incorrect/not possible) it runs better but still not great. He says it will then stall after 5 minutes or so". I can't imagine what this means. You can provide a constant 12V to the fuel pump to bypass the ECU controlling the power delivery to this, you could also I suppose provide a 12V feed to the coil, however the main function of the ecu is to switch the injector earth to provide fuel pulses and to switch the coil to provide timed sparks (this is based on the engine position indicated by the crank sensor and a combination of the MAP sensor and throttle potentiometer mainly, for load) but he would not be able to drive either the injector or the coil in such a way as to allow the engine to run. So again I can't imagine what his bypass is. 

 

 

So in summary - if it's got a throttle pedal switch, verify it is working or disconnect it and see how you go. If you still have any doubts about the O2 sensor, unplug it and see how you go,  if you are in any doubt about the vac pipes replace all including fuel trap with 'correct' ones (you can run silicone pipe and I have done this but I'd start off using 'correct parts' to know where you are first). 

 

Cheers

Craig