check engine light, rough idle...

It's early on a Sunday morning and I'm trying to figure out my engine problem.
Here's what happened.. (2005 4L)

We had a really hot day (100°F)
I was really low on gas.
My gas cap was defective (loose) but everything ran fine.

The next day I noticed that my "check engine" light was on and my engine ran really rough when moving. I filled the tank and bought a new gas cap. I've started the engine a few time but it's really rough... any ideas?

 

Truck needs to see 3 good " global trips "
Meaning cold start and run at temp for certain time and speed then a complete cool down and start again.
Some codes never clear and remain with a cel until scanned and manually erased.
Since you now have a drivability issue I suggest getting the system scanned.

If your tank was real low you could have sucked up some crap.

Start with a scan before you throw things at it you may not need.

 

I got a scan; it had 4 "loose gas cap" and a "cylinder 3 misfire." Gas cap is fixed now I need to investigate the misfire. Hmmm.

 

try swapping coils

 

Bad injector? Bad spark plug? Junk in the system from the tank being so low?...

 

It was a spark plug. However, I paid the local shop to tell me that. $160. Sucks to pay that much but it' a lot less than I was worrying about! I guess I just learned to change the spark plugs every 100k miles or so, eh?

 

From personal experience.. on another toyota vehicle.
Do it at 30k, 60k, 90k, 120k, 150k..
At those intervals I also change Rear Diff, Transfer Case, Front Diff, coolant
Transmission every 60k miles. That's just my choice. Could be too much too soon, but it gives me peace of mind and I am a DIY type of guy