Hi all, a couple of weeks I posted about a P300 code I had and it looked like I fixed the problem....but it just happened again tonight. I got P300 and P300 P. Although it wasn't as bad, it still stumbled. The symptoms today were, I was at Frys and I started my car and it took a while and it felt as if it was going to die but eventually it started fine. But when I drove it started stumbling. The RPM meter was fluctuating a lot at the stop light but it was just one. The rest of the stop lights were just fine. And I got home and everything seemed normal. I replaced the UIM/LIM gaskets already and it did seem like it solved the problem.

What I did do yesterday was clean the throttle body with cleaner and I cleaned the idle air control valve with the cleaner. Did I do something wrong? Idk but what else can be the problem?

was it after or before you cleaned it

After I cleaned it. I used the throttle bottle cleaner and it actually felt a lot smoother when I drove it. It started idling a lot smoother and it drove smoother on the highway. But the problem was when I went from store to store and at the last stop when I started the car it sort of hesitated and then the misfire check engine light flashed again.

Looks like I made a big typo, the code is P0300 and I also get a P0300 P. I also still have the P0171 and P0171 P. I hate these codes so much.

if its lean and misfiring there is air getting in after the maf. maybe the iac is not sealed or there is some other gasket that is leaking

Could the little o-ring be the problem? When I took it off, I noticed it slipped and it wasn't "snapping" back on. But I put it back on thinking nothing of it. I might have to replace the IAC because it looked awfully old. But would a faulty IAC cause the random misfires?

it could. i would make sure the iac is air tight first then see what you have from there