2008 Tacoma rough idle

2008 Tacoma. 4 cylinder. Changed valve cover gaskets and plugs. Used iridium OEM pre-gapped plugs. Now I have a rough idle. Had oil changed and CEL came on. They read a code about cylinder 2. Reset code and it hasn’t come back on. Have checked all the connections, replaced coil pack in number 2. Still rough idle. Almost dies when I stop. But, seems to run ok when I’m giving it gas. Ideas, suggestions on what to check next? Thank you.

 

Did this happen before the plugs were changed?
It’s not unheard of to have a bad NEW plug.
Have you switched the NEW plug?

 

Did you have the battery disconnected when you did this? Sounds like your throttle body is dirty, disconnecting the battery would reset learned idle values and if its dirty would cause a low/rough idle untill it's cleaned or it relearns on it's own.

 

I did disconnect the battery when I changed plugs and valve cover gaskets.

 

If cylinder is not firing would it be obvious? It sounds fine when the idle is above 700 or so. Just shakes a bit when it drops below 600.

 

Clean your throttle body and MAF sensor and let it idle for a few min and I bet it will be good.

 

Sounds like you might have a vacuum leak, you're 100% certainly you didn't forget a tiny hose somewhere? Fuel pressure regulator vacuum hose? All the electrical connectors are pushed on solid with no plug retention clips broken?

Do the coil packs Ohm within spec?

I always check the gap on plugs even pre gapped plugs. They're always off a tiny bit and sometimes off hugely.

 

Definitely a good idea to start by cleaning the MAF sensor and Throttle body. Also double check all of your harness connections that go to the coil packs. I have had a loose connection not cause any issue for weeks and then as the plug wiggled itself all the way off, a misfire started.

 

I agree with above. Once I bought plugs that were gapped properly, once.

I always center and gap new plugs. Quite often the hook is pretty badly off center.

You could try, engine running, unplug that coil on the cylinder you suspect, if nothing changes, it could be something else. If it suddenly runs worse it is something else.

Back track what you did, make sure everything is back on that’s supposed to be. As what was already said, everything plugged in tight, no vacuum hoses left off. Sometimes all you gotta do is stop, step back, think. You’ll figure it out.

 

Cleaning the MAF and the throttle seemed to have fixed the problem. While I was at the auto parts store I had them hook up their diagnostic tool and it didn’t show any codes. Attendant said if it had been misfiring there would probably be a code. Thanks for all your help.

 

Did you buy confirmed 'Genuine Toyota' parts??
Some online sources have poor quality knockoff parts.

Sorry. I missed your last post where you solved the issue

 

Awesome!!