I have a 2005 F150 and recently changed the spark plugs out with a set of Autolites. Ever since I changed them out, my truck has been giving me a lot of problems.

1. Truck has a hard time starting after it has been running for a while
2. It seems to idle low (truck used to idle at 800 rpms, now idles at 600 rpms) and rpms will fluctuate when when I come to a stop or put it in reverse.
3. Engine seems to run rougher than before

As far as I can tell, I hooked everything back up correctly. If anyone has had expercience with this, or has any advice, I would really appreciate it.

 

May need to change the coils and plug boots as well. Did you make sure the gap in the plugs was set right?

 

Autolites have been known to cause problems once in awhile. Also if you disconnected your battery when you changed the plugs the PCM may need to relearn your driving habits.

 

Swap the plugs out with Motorcraft plugs...problem gone

 

I don't have any experience with the brand of plugs you may have used, but if you did remove one of the battery connections when performing the plug change, that could be the symtoms of your issues. As the previous post mentioned, take the truck for a 30 minute trip in some various driving speeds (stop/go/cruising) and see if the PCM "re-learns" the driving characteristics.
Also check the COPS (coil over plug) connections to verify a tight, clean connection. If one or more are bad, you should have a stored trouble code.

 

I has similar issues and discovered that one of the plugs were tightened all the way. I had a strong smell of gas along with with same problems. I changed the COP and it ran much better but after I found the loose plug, all the problems were gone.

 

Thanks for the advice, I did disconnect the battery when I changed out the plugs, but it has been about a month since I did the change so the computer should be adjusted by now. This weekend I'll take the plugs back out and make sure they are all tightend correctly and take a look at the coil packs and boots. Has anyone else had a problem with autolites? I read up on them before purchasing and most people had good things to say about them.

 

I had a very similar experience with autolites. Long story short truck was running really rough so I tuned it up with autolites, and it didn't fix the problem. I had to tow it to ford 2 days later and 600 bucks and another set of plugs, motorcraft this time, and the truck runs better. We talked to autolite and we sent them the plugs and they reimbursed use the 600 bucks plus the price of the tow.

 

Make sure you didn't miss any vacuum lines. Symptoms sound like a vacuum leak.

 

No...symptons sound like the wrong plugs...