4 replies to this topic

[TimPickering92]

Hi All,

 

I was wondering if anyone could offer me some help or advice. My 1997 MPI is suffering from a high idle, and running rich (it's coked up the new RC40 exhaust tip, and you can really smell it...). I'm fairly sure it's down on power too. As an aside, but also possibly connected, on the first start of the day, she fires, then almost stalls, before settling at an idle of about 1,100 rpm.

 

I've used Rover MEMS and found that the O2 reading, and therefore AFR is all over the place - from about 12 to 17, just whilst idling. The coolant and oil temperature sensors seem to be reading properly.

 

I've...

 

Cleaned the IACV

Re-sealed the throttle body to inlet manifold (with gasket silicone as I couldn't find a replacement O-ring)

Installed a new Bosch O2 sensor (this had been re-located by previous owner to the Y-branch of the LCB)

Reseated the Y-brand pipes, as there was a slight blow (this and the new O2 sensor seemed to cure the hesitation issue I was having when on partially open throttle.

Set the tappets cold at 0.3"

 

I'm thinking that the most likely culprit is another leak somewhere in the LCB, or manifold gasket? I can't think what else would cause the AFR to be all over the place like that... 

 

Anecdotally, the Mini has chewed through about 3 O2 sensors in the 17 years it's been in our family! Makes me wonder if there's something more fundamentally wrong with the fuelling?

 

Any suggestions really gratefully received - thank you in advance! 

 

Tim

 

[timb2117]

I am sure you've done this but I have identical on the car I am restoring, '95 spi. - vac pipes, does sound like air is sneaking in somewhere, re set the stepper motor, check throttle cable for sticky, and maybe the throttle sensor on the pedal end?

[genpop]

Hi timb2117,

he is speaking of an MPI. This car has no vac pipes and no throttle sensor.

But I would check the fuel pressure. What happens when you close the IAC in total.Is the thermostat working or always open? What says Rover mems about the water temperature?A guy here on the forum complained simular problems.Everything was good after he had changed the water temperature sensor even this showed good values in mems fcr!

[xrocketengineer]

I would suspect the manifold gasket. Extra air getting in on the intake side would increase the idle speed. Extra air getting in on the exhaust side would fool the O2 sensor into thinking that the mixture is lean and the ECU would increase the fueling. At least that would be the logic. 

[TimPickering92]

Thanks everyone for your replies! 

 

I think after replacing pretty much every sensor I could, inlet/exhaust manifold gasket, I found it was the throttle position sensor. It was giving ridiculous readings (like, negative angles!). Changed the TPS, and the issue finally went away! 

 

Thank you for your assistance!