UK-POLOS.NET - THE VW Polo Forum

Have been lately trying to catch up with some much needed car maintenance on my polo. I have had some problems with the running of the engine, Uneven idle and having the car stalling when pulling away due to the cars revs being hesitant.

I have given the car a service including fuel filter change, which hadn’t been changed by me all the previous owners I believe. There were two engine warning light, one being the coolant temperature sensor and the other the lambda sensor. I changed the coolant temperature sensor yesterday, all of which went as planed apart from coolant poring all over the place . When I fitted the replacement sensor in, after about 10seconds the car made a sort of electrical groaning noise without the ignition being on, is this the car recognizing it’s a replacement part?
My other question is, the exhaust on the car is a pattern one, would this effect the Lambda sensor , as in, it need replacing all not?

I have not had any problem with the engine being hesitant or a irregular idle, since the fuel filter change and coolant sensor replacement, fingers crossed that’s fixed that problem!

The car is a 1.0L 2001 and is at 92,000miles.

Thanks

Sounds like you have a few issues.

A knacked coolant temp sensor will cause poor running as the car does not know if the engine is up to temperature and cannot introduce the right level of fuelling. It's only a little part but fundamental to optimum running of your engine.

The lambda sensor - what is the error you were getting? It doesn't matter if you have a pattern part as long as it's a direct fit and the location of the o2 sensor hasn't changed.

Not sure on the 1.0 but on the 1.4 16v AHW engine, the cat is part of the downpipe and the o2 sensor fits into it, and at the last MOT our was showing high CO2 so I ended up changing both the sensor and the cat just to eliminate either part.

While you were doing the service, it's definitely worth cleaning the air intake, butterfly and breather pipes - this will help with any spluttering problems too.

Hi, cheers for the advice.
I am not quite sure what the full error report was, regarding the lambda sensor just that it needed replacing.
Been driving the car for 10days now, since the coolant temperature sensor has been changed I haven’t had any problems with the engine, fingers crossed thats fixed it. It also seems to have a slight better performance as well, noticeable when driving up hills.

Will order up a replacement Lambda sensor within the next couple of weeks. What does the Lambda sensor actually control?
Also the exhaust and cat were only replaced about 3years ago.

Thanks

Lambda sensor will measure the level of oxygen in your exhaust gasses to determine how rich or lean the mixture is, and will send signals to the ECU to adjust the air/fuel ratio accordingly.

The sensor on it's own won't do this and the ECU will expect a cycle of readings from the Air Flow Sensor to measure raw air coming into the engine, as well as other sensors (some modern cars have many more sensors)

Anyways a knackered Lambda/O2 sensor will definitely cause poor running and poor economy.

Better explanation here

http://en.wikipedia.org/wiki/Oxygen_sensor