I have a 2007 Mazda with a 2.3L engine. A while ago the check engine light came on, and a few weeks later, I started having issues with engine performance.

The RPM will bounce at idle, and the engine bogs at pretty much all RPM's. It seems to work ok while I accelerate, for some reason though. I got the code read at a shop, and the fuel mixture was too rich.

I've taken it to multiple shops: first they swapped out the crankshaft sensor, that didn't work, then the MAF, didn't work, and then the exhaust oxygen sensor. This also didn't work. I took it to the dealer, where they told me that I needed a genuine Mazda MAF. This also didn't work. Each time, the fuel mixture has read as too rich.

Each time, the car worked for maybe a week before the same problem cropped up again. The last shop I took it to only found an issue with the MAF sensor, which has already been swapped out twice. I also had them check the wires and harness, as I've heard that can be an issue — they told me it was fine.

Any ideas what this could be? The computer maybe?