Oxygen sensor update

[pitpan]

Well you could knock me down with a feather, the release fluid I made did it's job, the sensor gave with a little pressure and I removed it with the sensor socket I bought from e-bay. The sensor was totally shot and had a piece broken off at the tip. (if someone could navigate me how to post a pic I would do so)

Anyway with the sensor changed I went for a drive, for around two hours it ran fine then all off a sudden the engine management light comes on when I come to a stop at lights and it starts to run lumpy with a erratic idle like surging, from 950 to 1500 down to 750 rpms then nearly stalls, but when I start off again it runs lumpy for a few yards then has a surge then back to normal. I still have to change the manifold O2 sensor but I am starting to wonder if something else is causing the problem.

[addo]

Did the "Stop" light come on as well?

[pitpan]

HI Addo,

No the 'Stop' light did not come on

[addo]

Maybe check the chassis to engine earthing, and the that the ECU case is earthed without resistance.

[pitpan]

At cold it runs fast idle but when its warm it runs fine then after about 45 mins running the EML comes on then it surges and runs lumpy at traffic lights when I wait for them to change.

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ok will do, does the earth from the ECU run from the box as I have never seen an earth cord there

[addo]

No, it is from two wires on one of the three connector plugs. You should have no resistance (or voltage) measurable between the ECU case and ground.

[pitpan]

ok I might have to take it to an auto electrician then

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come to think off it I do have an earth strap that looks like it is held together by a plastic tie, it is attached to the bonnet. is this the engine earth

[addo]

No, that's just earthing for the bonnet - it probably doubles as a safety strap.

[pitpan]

ok, everything looks like it is earthed properly, just took it for short run, at cold it runs fast idle about 1100rpm then after it warms up it runs at 950rpm, then after about 20 mins the temp if its out of 100 goes to around 70 then when I wait t TL's the EML comes on and it runs lumpy with the erratic idle. Then when I drive again it runs lumpy for a few minutes then runs fine and the temp goes down until I come to traffic lights and then the symptoms all start over again.

[addo]

I suspect it's related to operation of the cooling fan. You could try two more simple tests.

One is a light or LED wired in parallel with the cooling fan motor, this will show whether the problem is related to operation of the fan unit.

The other test is to take the engine temps (radiator, head, block) with an infra-red thermometer at various gauge readings to confirm accuracy or not.

You should also remove the ECU connector and make sure there is no corrosion on the pins.