MPi woes
Turbo Mini Forums

I am after some help regarding an MPi issue, applogies for long thread!

We have been trying to solve an issue with a Mini Mpi for some time and ran out of ideas by now.

9 out of 10 times, the car starts normally. Revs go up to 1300 or 1400 and then settle at 800-850 idle speed. I have been told that if it starts ok, the car can be driven without problems but haven't driven it (much) myself, so can't confirm.
1 out of 10 times, the car starts, doesn't go beyond 950 or 1000 rpm and settles at a irregular idle around 700-800 rpm. If so, it sounds a bit like it's running on 3 or 3,5 cylinders. It will rev, but splutters in the exhaust when the revs are going down.

Although I haven't been involved in solving the issue from the beginning, but I will try to describe what was done so far in an attempt to solve it.

- Lambda has been changed.
- TPS has been changed.
- ECU was exchanged for an ECU from another car.
- Temperature sensor was replaced.
- Injectors were exchanged for a set from a different car.
- The car has been with an engine diagnostics specialist where the cat severely overheated during testing. Apparently it was soaked with unburnt fuel which ignited.
- Cat was removed and a decat pipe fitted.
- Ignition coil was replaced.
- New plugs and leads.

Over the last week I tried a few things myself.
I started by replacing the idle control valve. Again, no success.

Yesterday I tried a few more ignition related things. Exhaust spluttering and overheating cat seemed like ignition issues rather than injection issues to me.

- Crankshaft position sensor exchanged.
- Replaced wiring between coil and ECU.
- Replaced plugs by Denso W20EPR-U. Was NGK BPR6ES if I remember correctly. (Solved an Spi issue recently that way so gave it a go...)
- Cleaned the camshaft position sensor. Only a very slight amount of swarf on there.

After another day's worth of trial and terror I gave up as well...

I have been told that the problem has improved, but the bad running every now and then hasn't been solved...

My thoughts are still towards a faulty cam sensor but since these are quite pricy I thought I'd post here first for ideas..


Anyone with experience/ideas about this type of problem?

Cheers,
Han

Dazed and Confused....

The wiring to the cam position sensor is a favourite for failing on these. A broken wire may show an intermittent fault.

If something is worth doing, it's worth doing half of.

That's quick!
Thanks John, will give that a look when I am with the car again.

Dazed and Confused....

very common is a failure at the sensor ground joint inside the loom. pink-black IIRC, quite close to the ECU

Danke Klas!
That makes searching for a broken wire much easier!

Dazed and Confused....

I have found that cleaning the earths on both sides of the engine bay solves a lot of intermitent faults.

Let us know what it is when you cure it Han.
Aren't the ECU and the alarm module 'twinned' on these?
And I'm sure there's a replacement wiring section available (from Minispares?) to replace a section that chaffs - can't remember what wire it was though (time for me to off and google now!).

Thanks Coop,
I will deffinately let you guys know.
The car is not not around now/no time to work on it now.
If you do find anything while googling I would appreciate it..

Will keep you posted.
Cheers, Han

Dazed and Confused....

Soo, to come back on this..
The grouds wiring was a mess, exactly as Klas discribed...
When renewed, sure enough exact same symptoms were there.

Any more thoughts gents?

Dazed and Confused....

Han go with John's recommendation.

What about the MAP sensor? especially if it is pig rich.

Coolant sensor in the inlet manifold.

There isnt one

You have to think what affects not only the fuel but also the ignition advance...... the MAP sensor.

An open circuit MAP sensor, the ECU will see a high value which will throw a load of fuel in an pull a load of ignition timing. The fact that the IAC is adding more air in an effort to increase idle speed while idle advance control is adding advance is probiably the only reason the thing runs, and why it sounds and runs like a bag of shite when the throttle is operated...... pig rich and little advance.

A cam sensor failure while the engine is running, the engine will still run perhaps a little worse that it normally would. A cam sensor failure with a stopped engine wont start or run. It says so in the workshop manual

my MPI was the same come to think of it my heads a shed, it failed the MOT 2 years ago with insane rich mixture, and run shit,

i changed the air temp inlet sensor on the right hand side of the manifold, its colourd green part number Elmwood ES110-1.
stamped on it

it sorted it for me retaining 43 mpg on a run. most rover cars were fitted with this like MGF etc............ its a common fault, especiall when the engine has been stood for sometime

hope this helps

OH their available on ebay

Cheers lads.

Steve, the cam sensor wiring was also replaced.
Will advice to replace the IAT and see if that brings something.

Thanks again,
Han

Dazed and Confused....

Surely if the right diagnostic equipment is being used you can eliminiate/prove ALL of the sensors?........ You should also be able to see the active ignition advance and IAC position, especially when the problem persists.

All this information should point towards the problem.

On a side note, I had a similar issue with the 1400Spi which turned out to be a bent valve that had worn the seat to that shape ( the head was after the all off the BMH 24 Lemans car, as was), anyway. There would be the odd occasion the engine would run like an absolute turd. The valve had rotated and was not not sealing properly.

Edited by Sprocket on 19th Oct, 2014.

In hind sight we should have, you're right.

Dazed and Confused....