Weird problem - K11 engine revs surge at low RPM

[robkw]

Hi All,

I'm looking at my daughter's 1998 Micra K11 (1.0). She doesn't have a lot of cash and so I am trying to sort out a problem for her.

The car starts fine, and runs fine when cold but once warmed up, the engine revs are not stable at low revs.

This only happens when the car is in gear (not neutral) and at low revs - it's just as if somebody is gently blipping the the accelerator about once per second. The engine revs surge between about 900 and 1500 rpm.

This makes low speed manouevers and crawling in traffic a bit of a nightmare - otherwise the car runs fine at a steady speed on the open road.

I have tried re-soldering the Air-Flow sensor and have run the ECCS self-check - all looks OK. The "Check" warning light is not coming on - so it looks as if all the ECCS sensors are OK.

Any thoughts?

Thanks in advance.

 

[MaxWheeler]

... If the live data looks normal and there are no obvious signs of 02 sensors giving false readings or a huge intake/manifold leak... then have you also checked the engine mounts aren't in tatters? That can make a big difference at low speeds and when changing gears because the whole enging jumps...