Toyota iQ Jerking Acceleration

Whoa, that sounds eerily familiar. I've got an iQ as well, although I don't know if the year makes a difference. I went through almost the EXACT same symptoms a while back – the jerking, the check engine light, the rough idle, everything. I was pulling my hair out trying to figure it out. Did you check for any hissing sounds around the intake manifold? And what codes are you getting? That would help narrow it down!

I was listening for hissing around the manifold, but didn't hear anything obvious. The error code that came up was P0171, system too lean (bank 1). I'm leaning towards the gasket since the car is getting old. I was hoping it was the O2 sensor, but the car feels like it's breathing through a straw. Is this the same problem you had with your car?

Yep, P0171 was exactly what I was seeing too. Honestly, I chased vacuum leaks for a week before finally giving up and taking it to a mechanic. They smoked the intake and found that the manifold itself was cracked due to scorching. So, while it could be just the gasket, don't rule out the manifold itself being defective. It cost me a pretty penny, 1180€ to get the whole thing replaced. I'd suggest getting a professional opinion before you spend too much time and money chasing ghosts.

Thanks a bunch for the insights! Sounds like I'm in for a trip to the mechanic. I was hoping it would be a simple fix, but a cracked manifold makes sense given the symptoms and the age of the car. I got it sorted. Turns out it was exactly as you mentioned - intake manifold leaking due to scorching. Replaced the part and the issue is resolved, cost me 1180€.