Toyota Matrix rough start

Hi, I have a 1.8L 2014 Toyota Matrix. Today I noticed it sounding a bit rough starting, but not bad. Then the yellow engine light came on. It runs fine once started and starts fine after running for a bit. I scanned the vehicle with my code reader and got the following codes: P0300, P0301, P0302, P0303. Does anyone know what this could be and what I should try to fix it before calling the dealership? Thanks.

Does the vehicle have to sit for a while when this hard starting occurs?


The misfires could be spark plugs, coil packs, fuel injectors, compression, bad gas, or something else.

What country are you in? There was no 2014 Matrix in the US as far as I can tell. Regardless, a 2014 is out of warranty so there is no need to take it to a dealer. An independent mechanic would most likely be cheaper.

Yes it has to sit for the rough start to happen.

I live in Canada. They made them one more year in 2014 here, but they are the exact same as the 2009-2013 model.

The next time the vehicle sits and you go to start it, turn the ignition switch on so the dash lights come on for two seconds. and then turn the ignition switch off.

Repeat this a half dozen times and then try starting the engine.

If the engine starts right up without running rough, it points to a bad anti drain-back valve on the fuel pump assembly.


I let the car sit for 10 hours and did the ignition switch thing like you instructed. It still struggled to start. Then once I drove it around and shut it off, it started up fine.

I wonder if coolant is somehow getting into one or more cylinders. I had this problem with a Ford Aerostar I once owned. It would run roughly when first started after sitting overnight, but then would even out and run just fine. The problem turned out to be a crack in a cylinder head. Fortunately, the van was under warranty. The dealer installed a new engine as enough coolant had leaked in to score a cylinder wall.