My 2010 (163k miles) has a really bad rough idle. It’s worse in park than it is in drive just stopped at a light but it’s still there. My RPMS dance around from 500-1k at the worst, but sometimes only wiggles from 600-750. It’s really rough with the AC on. It’ll drop to 500 and sputter and kinda catch itself and bounce back up to 1k and shake and even back out and keep wiggling around. Spark plugs & ignitions coils replaced, shop checked for vacuum leaks, replaced 2 of 4 o2 sensors. No CEL and no codes. My neighbor told me it’s misfiring but honestly I can’t feel it when driving. It drives just fine with sometimes sluggish acceleration and slight rough idle while stopped but otherwise fine. Taken to a couple shops over the last few months and no one has found anything …. please help me!! I am not mechanically inclined but I am trying !

 

Going on a set of assumptions that the new parts are good (new doesn't mean good) and the mechanics did a great job and couldn't find any leaks because there aren't any (and without putting a scan tool on to see values for ourselves) you are down to a few possibilities. A bad maf, bad fuel pump, bad or dirty throttle body and dirty/clogged injectors.

You can clean the Maf with Maf cleaner by disconnecting and removing Maf, spaying maf cleaner thoroughly and repeatedly on the maf and when dry, re-install. Some folks may say to carefully clean with a q-tip and spray but a sneeze and you are buying a new Maf (I have never used the q-tip but then again, i clean mine at least once per year.)

You can also remove the throttle body, take it to the bench and liberally spray with carb/throttle body cleaner and rags. Be careful opening the throttle plate. Treat it as if it were a newborn and you will be fine.

Fuel pump/fuel filter. I would really save that until i could put some guages and look at values.

dirty injectors...i dont know your history or gas preference but most tier-1 gas producers add plenty of cleaners but you can also add some Techron or stp fuel injector cleaner to a couple of tanks of good gas and that should help if it is a dirty injector.

Afterwards, perform an idle relean procedure. I am sure it is here in the forum , but if you cant find it, let us know and we will point you in the right direction.

Please remember none if us here have seen your car and are are guessing, thinking of things you can do yourself that may make a difference.

Let us know your progress and any additional questions.

 

I have cleaned the MAF sensor recently but I was too nervous to try the throttle body too. I’ve only put 93 premium in her but idk about the previous owners. I do run fuel injector cleaner sometimes but I don’t do it consistently so I’ll try that. I have a code reader that gives me live data but I’m not sure what any of it means but I do have screenshots of readings i’ve taken a few days ago if it helps

 

Keep driving it. Try to do loads like hills and hold when it's misfiring. About 99% you are going to get a cly misfire code, check engine. Likely coil and/or plugs. It takes like 50 - 100+ miles for these to finally code. Hold the misfire during, load may speed up the code for you to know which.

 

I'd run a bottle or 2 of fuel injector cleaner through it.

 

So my engine light did come on this morning w code P0430 but idk if it’s actually my cat or if my o2 sensors are bad or something else. And when I’m driving I really don’t feel the misfire at all I didn’t even know it had one so I’m not sure where to hold it

 

Yep told ya. That's the problem. Its is either the cats or your o2 sensors. You don't need to hold it now, because you already have it coding.

The O2 sensor would be the easiest to replace 1st. Before I replaced I would try a can of Lacquer thinner to a Tank of gas take for a long 30mins to 1 hour drive, and run it out. ppl will say this, and that about it but if it is a light that just coded and the Cat are just starting it may work. After the thinner if the code does not go away I would replace the O2 sensors next. If thinner nor Sensors, work it's the Cats.