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Rover Mini SPi Engine Misfire and Fuel Problem


For those who are driving a Rover Mini Cooper, Rover Mini Mayfair, or any Mini made between 1992 to 1997 (MK VI and early MK VII) with SPi engine, you should read this article if you are having problem with the SPi engine. There are many possibilities with the SPi and MPi engine and that leads to frustration and most Mini owners replace the injection with carburetor system. It is not really hard to maintain a SPi engine if you have the right mechanic and knowledge. Below here is an experience shared by a Mini lover and it should be very useful to all our readers who own a Mini.

First of all, SPi means Single Point Injection whereby there is one single jet that feeds all four cylinders. It is basically an electronic carburetor. The last generation of classic Mini built from mid 1997 to 2000 comes with MPi which is Multipoint Injection that has its own feed for each cylinder. See a 1998 Rover Mini Mayfair that runs on MPi engine.

Rover Mini Engine Misfire

It was a sunny day and I was on a Mini touring trip traveling from Kuala Lumpur to Penang. As usual, I fill the maximum fuel in the tank before the journey started. Well, the Mini that runs on SPi engine is really fun to drive and I couldn’t stop myself from driving the car up to 150 km/h (approx 93 mph). The entire journey is 300 km and my Mini was running good until I have traveled 280 km. I feel the engine misfiring and it feels like the fuel is lost even my right foot is stepped on the accelerator. I immediately stopped at a layby and have a quick check on the engine bay, management relay, all the fuses, and plugs. Everything looks good and the car is able to start like normal. Thus, I try to drive it again.

The car runs again but the symptoms keep coming. It feels like the fuel is gone for a second and then back again. I was forced to drive in this condition to the nearest mechanic and have him check the car for me. This is the symptom when I try to start the car and give it a hard sudden rev.

This is the list of what my mechanic replaced for me:

  1. Fuel Pump – My mechanic checked and sees the motor is running and he said it is working.
  2. Fuel filter – It has to be replaced once awhile because the debris reduces the fuel that can flow. The fuel pump is unable to provide enough volume to the injectors if the filter restricts too much fuel. Inadequate fuel volume will reduce power and may cause the engine misfire, hesitate, and stall.
  3. Spark Plug
  4. Spark Plug Wires (Spark Plug Cables)
  5. Ignition Coil
  6. Lambda (Oxygen) Sensor
  7. Fuel Trap
  8. All the vacuum pipe – The black (with green label) one from ECU to Fuel Trap; The black (with white label) one from Inlet Manifold to Fuel Trap; The red one from Throttle Body to Spi Air Box; The yellow one from Air Box Underside to Air Box Upperside hot air temperature control valve.

It has cost me a fortune to replace all the above-mentioned parts but the problem is still exists. Therefore, I asked for help from some of the experienced Mini drivers, owners, mechanic, and friends from MOGM (Mini Owners Group Malaysia). These are some of the suggestion I get.

Sam Daud: It could be the fuel pump or the fuel filter or the relay at the brake servo. Just give these a check.

Mini SPi engine relay
Relay – Mini SPi Engine Bay

This is the relay which located near to the brake servo. Sam says it controls the fuel. He also mentioned that the only way to check this is to loan a workable unit and replace the old one.

Sam Daud: How’s the smoke at the exhaust??

Sam Daud: May be the fuel injector is blocked.

Mini SPi engine bay
Mini SPi Engine Bay

The injector is located at number 14 in the image above. You will need to use L length key to open it up then you will see the injector (BOSCH brand in green color). There will be two pin, one is positive (+ve) and another is negative (-ve). Remember the position of both pins. The easiest way is to take a photo so that you will know how to put it back. Use a long nose plier with a clean rag to pull it out. Make sure you do it carefully as the injector is a fragile item. Use a carburetor or injection cleaner to spray the area around. You can also use an air gun to blow the injector but please make sure you use a minimum power otherwise you will spoil the injector. Restore everything once it is clean.

Well, the problem is still exists after all the above work is done. The symptoms? As shown in the video, the RPM goes up until 2500-3000 then the fuel lost. Sometimes it goes up to 4000 then fuel lost again. It is uncertain especially when I try to drive the car. Here comes another suggestion from Abang Rare where he mentioned that the temperature pressure compensator SPI TPC could be faulty. It is located under the throttle body. Here is the image of it.

temperature pressure compensator
Temperature Pressure Compensator for SPi engine

It is a very small round disc that compensates pressure temperature on throttle body on Spi and MPi engine. It costs nearly a 100 GBP and I decide to check on some other thing before checking on this item. However, the temperature pressure compensator can be tested using a multimeter. Nobody is going to replace it before they confirm it is 100% faulty. The members from MOGM are really warm, another member suggested me to check on the wires at the bulkhead behind the air filter. There are a lot of fuses and wires and it takes nearly an hour for my mechanic to check on that.

temperature pressure compensator

See also: 1999 Mini 40th Anniversary

The Real Problem

The problem is still exists after so many things have been done to the car. My mechanic took out the fuel pump and check on it again. The motor runs and it works normal. However, he noticed that the rubber seal (circle in red) is loosened.

Mini Fuel Pump SPi injection

This explained everything. My mechanic fill up the fuel tank over the green line and the symptom is gone. The problem exists when the fuel level below the red line because the fuel leak from it even though the fuel pump push the fuel up. This causes the engine misfire, hesitate, bad idling, and stall. The solution? Replace a new fuel pump that cost approximately 120 GBP or you can modify it with other powerful fuel pump such as the one taken from Nissan Skyline.

Modified Mini Cooper fuel pump
A modified Mini SPi fuel pump using one from Honda

See also: My Mini engine won’t start

Prevention and SPi Engine Maintenance

I’ve left my Mini for four years. I only start it three times in a year although the fuel pump is relatively new. Always keep your fuel level at half or above all the time to keep the fuel pump in good condition.

Last but not least, if you have experienced any problems related to your Mini or other cars and would like to share it here, please do not hesitate to write the story to us at malaysiaminilover [at] gmail.com or you may use the Contact Us feature in this website.


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