ASA Everyone.
Model: 2011
Engine: 1KR-FE 993CC
Milage: 100000
Location: Karachi
My Vitz 2011, is having intermittent jerks mostly when it is cold. Although this issue also happens sometimes when the engine is warm.
When I start the car it starts up nicely and after I start driving, within the first 10 minutes of the drive there are jerks which feel like engine misfiring.
The main headache for me is that very often these jerks make the engine stop when the car is standing still. Happens very often when I take out the car in the morning after a while it gets better and the misfiring becomes less of a pain, but it still happens at a lower frequency.
Suspected that it might be the wiring but popping the hood and aggressively pulling the wires has no effect, it doesn't vibrate or stop when I do this.
To get a better idea, I started my car cold, connected an OBD II scanner and monitored the O2 sensor 1 graph. And it shows spikes when this misfiring happens. I have attached two images which show downward spikes on the air:fuel mixture graph for O2S1 sensor.
How should I go about diagnosing the root problem? When I take it to the mechanic the engine becomes warm and this issue doesn't show up that frequently.
Took it to a mechanic, he removed the ignotion coils, added some tape to it, and put them back saying that he suspects the ignotion coils to be leaky. But since this issue did not happen in front of him, he wasn't sure. The issue is still there.
There is some history of an older fault related to the VVTI system, but I think its highly unlikely that the old problem is linked here: https://www.pakwheels.com/forums/t/vitz-2011-engine-shuts-down-on-ac/3013197
Any and all help is appreciated, JazakAllah
