Erratic running and weak mixture.

[Brian Hayes]

I have a 1.8 '93 Eunos which fell foul of the MOT through emissions. Up until then it had been running perfectly but when I collected it they told me it needed a new lamba sensor and presented me with a quotation to supply and fit the same. Not wishing to pay for this I fitted a new sensor myself and ever since have had very erratic running. On closer inspection of the plugs it would appear the engine is running weak. The engine backfires and runs very erratically, sometimes dying away on tick over and then bursting back into life with the rev counter fluctuating wildly.
I would be grateful for any advice as the car is not worth a lot and the garage is quoting an arm and a leg to investigate and rectify. Many thanks for your anticipated help and advice.
Regards
Brian

[snotrag]

Start car, allow to warm up.

See how it runs.

Unplug Lambda sensor.

See if it differs - it should run much richer with no lambda signal.

That will help narrow it down.


As an aside, cheap no-brand lambda sensors are known for being a bit rubbish too.

Discounting that, other problems could be weak fuel pump, no fuel rail pressure, blocked fuel filter etc.

[nitrodave]

My wifes m5 had similar issues after leaving it standing for over 3 months in the winter, although when i pulled the plugs they were wet with fuel. What are yours looking like?

Turned out to be faulty ignition leads. £18 later for a new set from the motorfactors and all has been well ever since.

Ours is a 1.6 mk2.5

[Brian Hayes]

Thanks guys, I'll try the lamba sensor unplug and new leads and let you know how it goes. The plugs are bone dry but very light biscuit colour.