So it's been a while that when I start the car cold in the morning I can feel the engine not running smooth. It's like knocking or pinging. The engine starts to run smoother after a few minutes, but the issue doesn't go away. I took it to a local shop and the guy said it was misfiring. He suggested valve adjustment and spark plug replacement for around $550.

I think I started to having this problem after I seafoamed the car many months ago. But it was not as noticeable.

I have done some research and this problem can be caused by many different things: spark plugs, coils, oxygen sensors, etc. Just don't know where to start. The car has only 54000 miles on it.

Any feedback is greatly appreciated.

 

Why dont you start by pulling your plugs to see if any are fouled out, if so i would recommend replacing them. another thing to check would be your egr ports under your intake mani plate on top of the engine, if clogged clean it out with coat hanger and brake clean. as far as valve adjustment i would not recommend that, on the newer honda products valve adjustments tend to be real solid and require little to no adjustment.

 

pull any codes to see if there is record of the misfires or other issues.

 

Not to be mean, but if you searched you would have seen an answer! The TL intentionally misfires a bit on warmup to help warm up the catalytic converters to reduce emissions and achieve a ULEV (Ultra low emissions vehicle) rating.

A valve adjustment should be done every 105K along with the timing belt and spark plugs. Be sure to use premium fuel!

 

I'll checkout the spark plugs...

There were no error codes last time I checked. I will do it again soon.

I am aware of that, but the misfiring or whatever it is doesn't go away completely. Even after warm up. It is fairly strong when cold, and gets dampened a few minutes after it is warmed up, but is completely noticeable.