Hey there. I've been having some issues with my 2005 Mazda 3 (manual 5 speed) lately and am not entirely sure where to begin looking. I first got the car a couple years ago for really cheap because it had real issues like misfiring, but it only needed to have the coil packs replaced. Once I did that, the problems all disappeared and the car ran great.
However, over the last month or so, it's been slowly developing issues again. First, it started having issues idling, the RPMs would start dropping well below 1K and now it's at the point where if I don't actively rev it from time to time while at a stop, it will eventually stall.
Then, it started having problems after fueling. Apart from the idling issues, it would drive just fine, but when I stopped to get gas, it would seriously struggle to start, to the point where i have to pump the gas to get it to finally start and then rev it hard for a little bit, ideally getting it on the road as soon as possible and driving it a bit hard so that it doesn't die when I come to a stop. During this time, I can also hear it making the occasional popping sound.
And just in the past couple of days I've noticed that even while driving, the RPMs are rather odd. Say I'm in 5th and need to accelerate a bit, I'll push in the gas and the revs will shoot up around 1-2K higher than I would expect them to be and then gradually fall down to where they should be, all while I keep constant pressure on the gas (that is, I'm not taking my foot off or easing up causing the RPMs to drop).
The last one hasn't been a huge issue (yet?), but I've definitely noticed it. I'll go to pick up my speed a bit and get a larger surge of power than I anticipate, only to have it cut down to normal just a few seconds later. There was one instance yesterday on the highway where the RPMs went way higher than I think they should have, but I was shoulder checking and had the music on, so I didn't hear it right away. I was in fifth going up a minor incline and it went to about 5K RPMs when I think it should have been about 2.5K or so.
I know it's rather difficult to diagnose over text, so I'm not expecting some miracle solution here or anything (although if you have one, that would certainly be convenient!), I'm just hoping that I can at least get an idea of where I should start looking. I can't bring it into a mechanic for the next little while and ideally if I can avoid it, I'd like to, but if all else fails, I will do that.
Thanks in advance!