Lack of power, rough idling.

[Ghia10]

I purchased a 2007 Yaris T3 three months ago, and the entire experience has been unpleasant.

I had the car for less than a day when the first problem surfaced, rough idling, no power (speed never exceeding 20km/h) and jerking while driving. Waited an hour for Toyota to fetch the car to find that it worked perfectly fine. They took it to the garage to find the problem. Two weeks later, it happened again.

The problem isn't persistent, but when it acts up it, it acts up.

The ignition coil and fuel pump have been replaced, but the problem is still there.

Am I the only one with this problem?

[Sedan]

Hi Ghia10,

I had the same symptoms in my '08 Yaris. Tried many things but could not find the problem. When I took it to the local dealer they said the oxygen sensor has to be replaced. After doing that things got sorted out. There was no check engine light to show the faulty sensor though. I asked them the reason for that but the reply I got was "some times the check engine light does not light up for such issues." Weird, but since my problem was sorted, I didn't bother after that.

By the way, the fuel pump is supposed to last for at least 80k before needing replacement.

[Ghia10]

There was no check engine light and no error code. Toyota did check the sensors but found no faults. I'm at wits end. The car is unpredictable and i don't want to cause an accident.

[bairjo]

Throttle position sensor may have a loose connection.

[Ghia10]

Could it possibly be contaminated fuel?

[barryware]

I'll vote for the O2 sensor.. Same problem but a different car (honda).

It ran fine till it warmed up. The O2 sensor was feeding bad data to the ecu in turn, it would idle ruff, stall, no power at all. I almost had to have it toe'd.

The dealer had it for three days trying to figure it out. There were no codes given because even though not reporting correctly was not broken to the point where it would show up defective via the mil. I am told that they just guessed and replaced to O2 sensor and that turned out to be the problem.

after that, someone told me that you can unplug the sensor. It will throw a code but the engine will now run in a "failsafe" mode. I never tested that but it sounds believable.

[Sedan]

Originally Posted by Ghia10

Could it possibly be contaminated fuel?

Low quality fuel can cause faults in the oxygen sensor. There are few methods of checking the O2 sensor for faults. Googling will help.

Do you feel a difference when you top up fuel?