EMS Warning Light (1999 Yaris)

[bigbodie]

I've been having a problem with my Yaris and I can't quite make out what is the problem.

The EMS warning light keeps illuminating from time to time, sometimes it goes off on its own accord but then comes back on, to add to that the engine idles in a strange way, to the point where you can hear the engine noise from the cockpit. At speeds she is fine, but I am finding the gear changing a bit lumpy when I put the gas back down...

It's merely a hunch, but I'm guessing the culprit could be a faulty/weak spark plug. But until I get the invoice from my last service I cannot be too sure

Could anyone give me a rough suggestion please?

[Bluevitz-rs]

By EMS light, are you referring to the check engine light?

It's possible you might have an O2 sensor on it's way out.

[bigbodie]

Yes the check engine light sorry. So how does an O2 sensor effect the engines performance? I'm not a highly knowledgeable mechanic sorry XD

[Bluevitz-rs]

The O2 sensor measures how much gas/air mix that was burn inside the motor. If the readings aren't right it will effect how much gas will get injected.

If you can, bring your car to a parts store and have them check the codes. If the light has come on, there should be codes in the history and it should tell us what's going on more clearly.