I started my car yesterday and it took a second or two longer than normal to start up. Then, there was a rough idle while in park. When driving normally no issues persisted.

Parked, turned car off and then back on, no issues. Sat for about 10 minutes, turned car back on, same issue with rough idle.

No check engine light, but I scanned it with an OBDII scanner. The only code is P1399

Im not sure if I should look into spark plugs or coil packs. Car has 155k on it.

 

When was the last time you changed the plugs?

 

I'm not 100% positive on that one.
I just started keeping a maintenance log (since I do all the work myself) about 2 years ago. I have no record of changing the plugs, but I would have to guess that they were probably changed around the 90-100k mark.

NGK Iridiums

 

Check the 2nd Gen "DIY" sticky for common issues and fixes.
When was the EGR passageways last cleaned ? Also, the TB intake and IAC valve could be gunked up. Run some fuel system cleaner in the next tank of gas. Check for vacuum leaks. New NGK plugs and an air filter might help.

Do the easy stuff first, then clear the codes and see if they come back. If so, then ya may have a bad coil or fuel pressure issue ?

 

Thanks!

EGR and TB were cleaned about 2-3 years ago. Intake manifold and TB spacers were installed around the same time.

What's the best way to check for vacuum leaks?

 

Just inspect all the various vacuum hoses and connections for leaks in general.
Check the intake and air box for anything loose.

 

AEM Cold Air Intake filter hasn't been cleaned in a long time. Probably a good time to get that cleaned out too.

Side note: Any way to make those filters dry out faster after cleaning them? I always feel like I need a whole day to do that because of dry time.

 

Does it always happen ? Next time try letting the fuel pump prime before starting.
Check the ground cables that go to the trans 2 of them.
If I remember you had the trans rebuilt right ?
P1399 is a Honda code for Random misfire, same as P0300

 

No. Not always. Very intermittent over the past day.

Yes. The Transmission was replaced with a rebuilt one from Acura at around 100k. Where are the ground cables?

 

Follow the negative cable (Should Be Black) from the battery, it should lead to a bracket on the case of the trans, if its loose tighten it up

The other one is located under the intake tube, attached from the body to the trans.

 

Check the main ground cable from the negative battery terminal to the tranny.
Sometimes the bottom part of the cable near the tranny is exposed and tends to go bad. If in doubt, replace the ground cables with new ones.

 

Number 11, correct?