Erratic Revs

[kel123]

Hi all, your expert advice is needed!

My cars problem has developed over time rather than overnight so here goes:

The idle speed is erratic about 50% of the time to an extent that it stalls, this is not all the while, as I said 50% of the time there is no problem. Once it as held at about 600 then it stays there with no fluctuation. If I take the revs up high and release the pedal, the revs drop steadily, hold slightly at about 1200 and drop to 600 – sometimes as it drops it drops below 600 and then starts a to and fro until it eventually stalls. Unsure if this is part of it but the ‘engine emission light’ is on constant. Haynes recons that there could be a vacuum leak but I cannot find one, although there is a very soft repeating ‘t’ sound coming from that area. The chain was changed about 15000 miles ago and the car as now done about 69000, there is some rattle but only slight.

Because I do low mileage and had not given it a blast for sometime I added some injector cleaner to the petrol, I got better fuel consumption but it didn’t cure the problem – I have also changed the plugs, air filter and oil – I have also checked to earth and there are no problems?

Performance wise she still holds her own and pulls a 12000kg caravan with little effort

Any suggestion

1.8 club, 52 plate, saloon. (reprogrammed 2 years ago due to replacement of airbag ecu and electrical spikes/problems – it was reprogrammed to Si specs not club (not my doing))

[TimTay]

you say your timing chain is rattleing, pretty sure there all belts mate.

wonder what the rattle is

[kel123]

Too old to know the difference

But read the thread containing the info about the cooling temp sensor so i'll start from there.

[TimTay]

do the pedal test as well mate to get ya fault codes will be a good start

[ChrisBilly]

My 1.8 had the same problem, but would rarely stall. It turned out to be a leaking egr, it was sucking air from the engine bay and causing the car to run rich. I only discovered it was the cause after a member on here suggested spraying carb cleaner on/over/around the egr while the engine is running at idle. Sure enough the engine cut out, so i knew 100% the egr was the cause. I paid ~£20 for one from a vec b at the scrap yard.

[kel123]

Thank you TimTay I did not know about the pedal test – so I did it:

There is an error in the cruse control which I already knew about – it’s set up as a Si not a club!

P0100 Mass or volume air flow malfunction

P0134 02 sensor circuit, no activity (bank1, sensor 1)

P0170 Fuel trim malfunction

My guess is that these 3 are inter-related

[rushy]

Lambda sensor mate

P0134 02 sensor circuit, no activity (bank1, sensor 1)

[kel123]

Ok! what and were is the lambda sensor

[kel123]

From my readings I assume the lambda sensor is the 02 sensor on the ex. manifold

[rushy]

Yes mate, there is most likely 2, one before the cat and one after.