New Spark Plugs, rough idle

I changed my spark plugs this weekend. No issues prior to the chagne. Now, I have a rough/surging idle when it is in gear sitting at a stop up to about 5mph. All the lines are hooked back up so no vacuum leak that I can tell. Checked to make sure everything was clipped back in on the packs.

Thanks in advanced for the help.

 

What spark plugs did you buy and what gap do they have?

Try disconnecting the battery for 5 minutes - for the sake of the ECU needing a reset (so to speak)

 

sounds like you've already reset the battery. If so, just drive it for a while, it needs to relearn...

 

Double check your vacuum lines too. The one on driver side I forgot to hook back up and it did exactly what you are describing until I noticed it. If not that, maybe check your gaps on the plugs
edit: just re-read, noticed you had already checked the lines.

 

There's something else that I personally ran into while changing the plugs...Although, I can't remember exactly....

There was a sleeve or collar (or something) that didn't allow the pak to fall down far enough onto the plug tip. I think I remember I had to take everything apart and straighten the thing out....??

The only reason I noticed it, was that it didn't FEEL the same as the others when I installed the pak. Otherwise...it didn't look different.

Hope that made sense?

 

Is your check engine light on? If there's a misfire, you could start where your check engine light is trying you where your problem is.

 

How bad is it? I am curious if you might have accidentally reconnected the plug wires wrong. Obviously from your post there was nothing wrong before. I suggest checking the wires first, then double check all of the other lines. Make sure you didn't cross a vacuum line either that may be causing an issue. Go from there.

 

Also pull the plugs again to make sure you didn't bust any of the ceramic insulation.

I helped my sister replace her plugs once, and she got a little over exuberant with the socket and broke one of the plugs when she was removing the socket.

 

Thanks for all the input.

I have not disconnected the battery. I'll do that when I get home and see if it helps at all.
No check engine light so I don't think it is missing or that would throw a code.
If the battery/ecu reset doesn't work, I'll pull the plugs this weekend and make sure I didn't mess one up somehow. Pretty sure I didn't though.

 

Bonehead move of the weekend. Took the number two cyl plug out, looked good. Took out the number four cyl plug and what did I find?? Zero gap in the spark plug. Put in the correct gap, reinstalled, and idles as smooth as can be.
Thanks for everyone's input. BTW, check engine light came on during the drive home.

 

Wow were they not pre-gapped? Mine were pretty close to spec. Good thing it was something simple and you found it without too much trouble.

 

It also could have been bumped during installation.

 

Just an FYI, codes can be stored and still not trigger a check engine light.

X2 ---- it takes very little bump to accidentally close the gap on a spark plug.

 

Just did this... and realized I forgot to attach the PCV return line . Runs great now.

 

Old thread, but fits my experience perfectly. You guys have provided so much great info, here's my tale of dumbass that might save someone some cash and grief.

2010 DCSB 4.0 127K, installed new Densos gapped to .043. Before swapping the plugs, took the opportunity to "detail" the engine compartment. Finished the clean up and plug change, started the engine and it ran like crap. Lumpy idle, stalled a couple of times, check engine light and P0300 code. Also bank 1 and 2 lean.

WTF did I do, been wrenching for 50 years, how do ya screw up a plug change? I never disconnected any vacuum lines during the job, but this sure was acting like a leak. Turns out when I was on the stand leaning waaay into the engine compartment, my fat gut must have snagged the vacuum line on the throttle body and pulled it off.