5 replies to this topic

[Avl_Paul]

It is a 1995 Mini Cooper SPI. When I start the car from cold (ie. engine hasn't been running but ambient temps are in the 50-60 Deg F range), the idle speed on the tach reads ~650 RPM and the speed fluctuates up and down. Disconnecting the plug to the stepper motor doesn't change a thing! I've checked many of the vaccuum lines but still need to pull the ECU tonight and check the MAP sensor line. I am suspecting the following possibilities but need some feedback:

1) Inlet Manifold Air Valve: Not even sure yet if I have one and where it is but it would make sense that this is erratically controlling the idle (perhaps because of a dead sensor somewhere). Question: do I have one? If so, where is the electrical connector. I would like to disconnect it and see if that kills the engine or stabalizes the idle.

2) Stepper motor doesn't seem to be doing anything during cold start. I can hear it "clicking" when I turn off the car so I know it is alive in there. Unplugging it doesn't change the idle performance - should I be concerned?

3) Intake manifold heater - I have heard this can affect idle speed during warm up. Would it really cause the idle speed to fluctuate like I am seeing? Can you access the power cable without pulling the intake manifold in order to check resistance across the heater element?

4) Coolant Temp Sensor - I presume if it is reading off, the control system could be responding and causing the low idle condition. Any advice on how to confirm? Again, unplug it?

I don't have access to a diagnostic tool now but will get hold of one in a month or so if this problem can't be solved.

Thanks folks for all the support!

[Avl_Paul]

Some additional info:


I pulled the ECU tonight and checked the Manifold Pressure vaccuum lines - they are all holding vaccuum fine and had no fuel in them.


The car appears to have a metal intake manifold and I find no sign of the intake manifold air valve so I am starting to believe that, even though it is a 95, I don't have one. Can someone confirm?


I quickly checked the TPS and that seems fine. Unplugged one of the leads to a sensor in the radiator (CTS most likely) and that had no effect. Unplugged the TPS and that had no effect.


So, I quickly coming to the hypothesis that the problem is with the stepper motor. After all, it should be controlling idle speed and doesn't seem to be. I had my wife key on/key off the ignition while I had my finger over the plunger from the stepper and I can feel "clicking" but do not detect any real movement inward or outward. I assume I should be able to?


If the stepper wasn't working, would that result in a low idle (and possible wandering idle speed) before the engine heats up?

[Sprocket]

There is no Idle air valve on the SPi, that function is carried out by te stepper motor. The stepper motor is some times called a throttle kicker, as it acts directly on the throttle.

Id definately sounds like there is an issue with the stepper motor. The stepper motor shold be holding the throttle open. Idealy it will be at 40 steps and the idle speed is then controlled with the ignition advance, if the ignition advance is +- 5 degrees from the igntion map at idle, the stepper motor will then operate to allow more or less air in, the ignition advance then reverts to the map value and ignition idle control is resumed.

In your situation, the stepper should be operating to increase the air entering the engine, but it is not, the fluctuation is caused by the ignition advance trying to increase the idle speed.

You will have to dismantle the stepper motor and see where the problem lies. Remove the motor from its housing, and test it as you have, but now you can see the cam and the plunger operating.

I would also hazard a guess that the idle air screw has been adjusted incorrectly.

The only real way to properly rectify this is by tuning the idle air and stepper motor, by connecting a diagnostic, and adjusting the steps to 40.

Ensure the throttle cable is correctly adjusted and that the stepper motor is operating correctly before the idle air and stepper are tuned

[Avl_Paul]

Thanks Sprocket - this is the exactly the feedback that I need. I will look into whether I can get access to a diagnostic tool through a Rover shop here in town today. I should add that if I throttle the engine quickly when it is still cold and idling low, it will sometimes backfire through the throttle body. After reading one of the pinned topics, I saw that this is often caused by bad MAP readings. So, I need to confirm that I am not just mistaking how the stepper motor is supposed to work.

Can I ask a few clarifying questions?

1) If the stepper motor is working, how much does the cam move? Is the movement of the throttle plate and cam clearly visible if watching with the air filter assembly removed?

2) I don't see the idle air screw referenced in either the Haynes or Rover MEMS document, I assume you are referring to the screw on the cam that the stepper motor cam acts on? Is that correct?

3) Is there a document that states how to adjust that and how to set the motor to a certain number of steps when you do have the diagnostic tool?

[Avl_Paul]

Success at last! While I was troubleshooting this problem, I spent a lot of time on this forum searching old threads. Too often, people forget to post the solution to their issues so I wanted to make sure I posted the solution to my issue (and I finally now have the car back on the road!).

Just wanted to post that after months of troubleshooting and parts, I finally had some success troubleshooting my Mini SPI fuel injection system. Hopefully, others withl similar issues can benefit from my experience. After in depth troubleshooting, I'm convinced that the SPI is that bad of an injection system and it is worth troubleshooting. The car is a '95 Rover Mini Cooper SPI with the 24-way fuse block and immobilizer system. The problems were building over time but the main issues were characterized by:

1) Unstable idle when engine cold

2) Stalling or power loss when first accelerating cold

3) Battery draining to dead within a day or two when parked (due to ECU holding the main relay closed all the time)

4) Eventually the engine would crank but not start at all (no fuel). It would start and run fine if enough fuel or carb cleaner was sprayed into the intake to get the system running.

5) The fuel pump was not running when you first keyed on.

6) Stepper motor move (40 steps) at key off as designed. ECU can only vibrate stepper - no movement.

7) And finally, as if I needed another problem, it stopped cranking over at all midway through my troubleshooting.

First, I figured out the car would crank if I bypassed the immobolizer. [That turned out to be due to the key fob losing its synch with the immobolizer. Pressing the button repeatedly 4-5 times resynched and that problem went away.]

Next, I spent a ton of time ohming everything out and checking voltages all over the place. I confirmed that the relays and fuel pump all worked if I controlled them directly from the ECU connector with ECU disconnected (email me to find out how that works). The wiring all seemed correct and the only source of incorrect voltage was from the ECU and I couldn't be sure of that. I confirmed through bench testing that the stepper motor worked fine outside the car and only "vibrated" during key off, I was strongly suspecting ECU fault. Also, the ECU never opened the main relay after key off.

The next major breakthrough was when a forum member in the U.S. was kind enough to supply a Sykes ACT diagnostic tool which revealed that the coolant temp sensor was not functioning (not root cause of above problems) and the ECU was not reading the TPS at all (even though the TPS was confirmed to work). And the stepper would not work when commanded by the diagnstic test (again suspected ECU).

When I later took the intake manifold off, I discovered that the CTS sensor was just unplugged but I went ahead and replaced both the CTS and Lambda sensor as I had already bought the parts from the UK.

I managed to borrow an ECU from a friendly Mini dealer and, although it wasn't synched to my immbolizer, I popped that ECU in my car and it resolved most or all of the non-engine running issues: the stepper motor now operates exactly as expected, the main relay turns on/off with the key switch, the fuel pump runs when you first key on! Confirmation at last - a bad ECU!

Next, I bought an uncoded ECU off a member from TheMiniForum and now the car runs great! As I was tearing into the car to replace sensors, I went ahead and replaced my water pump, re-wrapped a lot of my harness, repaired the radiator, replaced the engine-steady bushes, replaced the engine steady mounting bracket (rusted), replaced all the water lines, replaced the fuel filter &replaced the fan. Hopefully, I can drive the car for a while trouble free!

Thanks for all the help from many different members of this forum. I really feel like I understand how this fuel system now works - I just wish someone had suggested a bad ECU much earlier!!!!

Best regards,

Paul

[Sprocket]

Really glad you got it sorted. Dodgey ECUs are few and far between, the manufacturers design these things to take some abuse, remember, they are designed to survive many tens of thousands of miles in one of the harshest environments known to man next to outer space and the depths of the sea The ECU should always the last thing to be suspected as the fault as its easier to test all the other components. . You can now see how easy it is to find faults now with the service tool. That is the Key!

Now go and drive it hard