I would like to preface this by apologizing for my lack of knowledge on cars, this is the first car I’ve ever owned.
anyways, i just picked up a used 2004 mazda 6 s (3.0L v6 manual) with around 146000 miles on it. the car runs and has gotten me from place to place as well as i could have hoped, but the engine makes a weird noise. the noise is almost like coughing or pop-corn popping(ive only noticed it when the car is moving, not at idle), from what i can tell it doesnt really happen around a specific rpm.
Another thing i noticed is that the car shakes when i turn on the ac, and one time when i was idling it stalled out just from turning it on.
A friend of mine said that “it could use a tune up” which im assuming they meant it could use new things like a new air filter, spark plugs, ignition coils or things, but im not sure.
I know this is probably confusing and not helpful enough, but I was wondering if its something simple like just swapping spark plugs, because thats something that I would feel comfortable doing on my own(after looking up how to do it)
Also i plugged in an obd scanner and didnt get any errors.
Most vehicles recommend spark plug change around 100,000 miles, yours may be overdue. Review, as suggested the YouTube video on changing in the plugs. Air filter change is relatively simple.
Before we go any further is your check engine light on?
are you sure it is coming from the engine? you can have 2 problems. the running rough with A/C on and then the popping sound which could be from your suspension or a loose heat shield or something else that is loose and vibrating.
I would hope that this coughing/popping is not a sign of low compression on a cylinder or two. That would be worst case scenario and could also cause an RPM drop when the A/C is on.
If the spark plugs come out I strongly suggest a compression test at that time. If there is a serious mechanical issue that is the time to find out about it; before loading up the parts shotgun.
I can’t offer anything better but the popping sound should be heard by a mechanic. A code reader is fine but a diagnostic computer will take a look at the readings from the various sensors to see if anything is out of the ordinary. Might be worth the $125 diagnostic fee to have someone check, but for sure have the popping and stalling checked.