Hey guys! I have an 09 Honda Fit going on 190,000 miles.
I've had this baby since 0! I've never had one issue, I've changed a belt or two but that's about it. It's been running a little rough lately, the only change that was made was my dad accidentally put in synthetic oil instead of the regular stuff I use..
I made a video not sure how to upload from my phone. Please help

 

Upload it to youtube and post the link here. The oil shouldn't make a difference, unless it was a different viscosity. I've been using synthetic since ~20K miles and have 172K on my 09 Fit now.

 

Your recent oil change should have no effect on what you have described. If you have 190k miles and still the original plugs you are way overdue to replace them. Normally should do that around 105k miles. Also check your air filter if that has not been replaced in a while. Is your check engine on ? If so have the codes read and report back. Start with the simple things first...

 

Have you done a valve adjustment?

 

If it's a rough idle where it's coming to or nearing a stall it's likely the coil packs. Easy fix and there's threads on here that describe how to test them.

 

I got the valve adjustment and changed the spark plugs. They said everything else looks good. I do need to change the air filter and the cabin filter. The tapping is gone but now the engine almost sounds gargled.....

 

Oh and I replaced the belt tensioner

 

I agree that the oil shouldn't have a significant impact on idle speed unless you put in 50W and you live in a cold climate like Canada. If anything, synthetics tend to provide a lower starting viscosity, like 0W or 5W, than regular oil.

I also wouldn't jump to the conclusion that you need to change any coil pack that sits on a spark plug, since you'll have a Check Engine Light (CEL) illuminate on your dashboard and you haven't stated that you have any CEL on.

I would start with the simple stuff. Look to see if your engine air filter is extremely dirty. Change it if you have 20,000-30,000 miles on it. Also look at air cleaner box and the ductwork and the tubing downstream of the Mass Air Flow device prior to the intake manifold to make sure it was put together properly. Any leakage from a mismatch in gaskets / tubing will bypass the Mass Air Flow device and the fuel / air ratio will be n error and cause idle & running issues if not stop the engine completely.

Report back what you find. Again, let us know if the CEL is on since it will also provide a code to what is wrong.

 

No check engine light and I have also changed both air filters. Everything is going pretty good. I'm probably just paranoid because of the high mileage.

 

If it was me I'd order a set of coil packs and swap them when convenient run a can of injection cleaner through it at least a couple times a year especially right after the winter summer gas changes..

The coil packs are a service item in my experience on japanese cars, the hitachi and denso packs just seem to have a finite life expectancy. I figure 200 bucks every 100K miles is worth the not having it crop up on a road trip or something. Then keep the old set on a shelf as a emergency spare.. Heck put one in a box and stick in in the spare tire well..

 

I'm at a loss why anyone would spend $400 on 4 coil packs when there is no indication that there is a problem with them - No CEL / Code indicating a misfire.

Until there is a Code to tell what the problem is, I'd keep running the coil packs that came with the car.