4 replies to this topic

[Paulwhitt20]

Hi,

I have had my mini for a few weeks.

It’s a 2001 1.3 Cooper mpi . As far as I know it is standard apart from a Stainless Steel maniflow centre exhaust that has been fitted by the previous owner.

When accelerating and driving on fast roads (>40 mph) it is fine but when driving round town or in traffic jams it is very jerky (kangaroo) in 2^nd or 3^rd gear at 20-30 mph (<2000 rpm) to the point I have to dip the clutch. When I ease off the throttle the car seems to jerk and again when I apply the throttle. I have also noticed that the tick over hunts slightly – more noticeable by the noise than any movement in the rev counter. It idles at about 900 rpm when warm. If you dip the throttle the revs increase then drop to about 1500 rpm then drop to 900 after a second or so.

It has not been used much within the last two years until I had it, but had a service and MOT in May with no advisories. I have no record of what was done at the service but the oil looks clean and the plugs look new. Oil filter also looks new. I have done about 200 miles in 3 weeks.

What I have checked so far by looking at similar threads on here.

The engine mount seems okay. It moves a bit if you pull on it really hard but I don’t think that is the issue. I have checked the wiring to the MAP sensor and that all looks okay but notice there is a cable tie that has been cut on the throttle body so the MAP sensor cable is not fixed securely to the throttle body. There does not seem to be any obvious leaks in the hoses apart from where the coolant pipes connect to the pipes that go into the heater matrix inside the car. Here there is some corrosion around the jubilee clips. I also notice a hissing (possibly from the coolant expansion tank) when the car cools down – is this normal? The temperature gauge reads normal and is in the middle when warmed up. On longer journeys the fan does come on if stuck in traffic so this seems to be working correctly.

There is also an oil leak from underneath the car. I think this is from where the gearbox linkage goes into the gearbox. The clock also loses time.

I have checked the plugs and they have a brown deposited on them but look normal. When I took the HT leads off I noticed some brown dust come out of the connector (rust?) so the next step is to replace the HT leads.

Would plugging it into an ECU diagnostic tool (ACR4) reveal which sensors may be faulty or is it trial an error at replacing each sensor one by one?

Any ideas on what to try next?

Thanks

 

 

[bloke]

Not wanting to bring a downer on things, but the late Minis have a rather tall gear ratio, what you described above is exactly the same on mine. Changing the gear ratio to a less tall one does help, that will reduce the achievable speed on the motorway. The upside is acceleration will be sharper.

 

It sounds like your sensors are working fine, but it's well worth having a diagnostic tool anyway, just in case something does go wrong. 

 

It's all down to backlash in the gearbox, the more worn it is, the more backlash. The revs do vary slightly throughout the entire rev range, this is just the engine management coping with a 50-year-old engine.  

 

The difference between my John Cooper Limited edition, and my mums mini Rio, which is a carburettor equipped Mini, is quite pronounced. You can put around half throttle all over the place in the Rio, and you only notice a slight kangarooing if you try hard, whereas in mine, you only have to take your mind off driving for a second, and unless you're gently accelerating or decelerating, you start bouncing down the road, to much embarrassment. 

 

It's something I've got used to. To improve matters little, I made up my own spark leads with the correct solid copper wire with resistive NGK plug ends. This allowed to resistances of each lead to be exactly the same, I also fitted good-quality champion spark plugs. This combo allows the engine to run as smoothly as it can. 

 

As I say, sorry to be the bringer of bad news, but hopefully the above improvements will make it less tiresome. 

 

All the best from Bloke.

[Guess-Works.com]

Get hold of the top of the engine and push it backward and forward, if it moves any more than a few mm, then you engine steady bushes are knackered which will account for the kangaroo'ing...

 

Also, the mini gearbox does note really suffer from backlash in the gear, but MPi's do have a known issue with wearing out diff pins and spitting them out the back of the gearbox... I suspect of you have 'lag' in the transmission it is most likely the diff pin, simple way to check is to lift one wheel off the ground and after sticking the gearbox in gear, see how much free play the wheel has, no more than 30 degrees ( 1 hour on the clock face )

[Ruckus]

Just to add

 

"It idles at about 900 rpm when warm. If you dip the throttle the revs increase then drop to about 1500 rpm then drop to 900 after a second or so." this is normal

[Paulwhitt20]

Thanks for the replies its put my mind at rest if they are all supposed to be like this. It's not bad news if means there is nothing wrong with the car. I thought they might be designed like this as the gearing is set up for motorway speeds. With only four gears to cope with 0 to 80 mph you will not get a perfect match for gear, speed and revs all the time. I will have to get used to it. Anyway it won't be me driving it most of the time. My usual drive is a Lexus cvt hybrid which drives very differently.

The backlash in the gearbox is about 15 degrees in each of the four gears so this seems okay at the moment.

I've put new ht leads on as well so that may help.

Thanks