So I got all of my plugs changed but now I have a hesitation/delay when pushing the throttle and a rough idle. The idle is lower and surges a couple hundred rpms while sitting still. If I turn the wheels and attempt to back up and left off of the throttle it acts as if it wants to die. It will also act like it is going to die when coming from speed and just letting off of the throttle.

I did have a very difficult time with the passenger side rear plug. Could I have hit a vacum line that I need to check. I am open to suggestions. The plugs frustrated me substantially.

The truck did not do this prior to the plug change. I have not changed the fuel filter, or any other sensors.

Where should I start and is there a vacum line that is commonly hit when doing the plugs on this side?

2005 F150 4x4 5.4L 3V

Thanks

 

what brand of plugs did you use?

Did you break any off? If so did you get all the pieces out?

From the sounds of it you either have a COP that went out or you have a plug that is not seated properly. You could be the victim of a stuck injector that just happend to coincide with your plug change; or like you mentioned you might have unseated a vacuum line.

 

I used Motocraft plugs. I did break one off but it came out very clean with no chips and I vacumed the plug well out before extracting with Lisle tool.

No check engine light and I figured a cop misfire would throw a code. Or do I need to do a wot run to get it to miss enough to throw a code.

This morning it acted differently. No searching idle but did have hesitation and when coming to a stop the RPMs dropped momentarily so low the lights dimmed and placing into reverse, cutting the wheels to back into a parking space it almost died due to the rpms dropping.

Does this seem more like a vacum issue? My old plugs were worn pretty well so could the new plugs be exposing a bad cop now?

I don't want to go replacing 10 sensors to find out a simple vacum line was off. What is the best way to check for vacum leaks?

 

You can get a vacuum gauge from the local parts store and see what you have for vacuum. I would also check all of the lines and make sure your intake is seated on top of the throttle body.

 

Recheck that last plug. I got a few more turns out of mine after having these same issues. Did you disconnect battery and remove computer to get better access to that plug?

 

I just did mine this past weekend. I had a misfire on 7 a while back (driver side second from rear) and I found that the spark plug wasn't even finger tight. Make sure they're all tightened to 26 ft-lbs (box said 23-27 ft-lbs).

You can also get COP's for relatively cheap. I think I paid $140 for the 10 that I got and all of them worked beautifully. I also changed the injectors while I was in there, same $140 for 8 injectors.

 

I did remove the computer and bracket to get access to that last plug on the passenger side. I also disconnected the battery.

I also torqued them all when doing the change.

I think I have a manifold issue now as well based on some sound and threads on here.

I did replace the TP sensor as well when I did the plugs do to the truck randomly dieing while in motion prior to the plugs being changed. But this only happened very very seldom.

I am just confused as having a rough idle and I noticed that WOT acceleration is not what it should be. I have done the trick of key on position and pedal calibration with a little improvement but the improvement goes away.

I am getting to my wits end with this Ford Truck as the spark plugs, idling, vibration in the front end even after having the tires rotated and balanced several times, no WOT power.

I have always been a die hard Ford fan and I think this may be a simple problem that I don't want to exaggerate the work I put into it so it doesn't leave a more nasty taste in my mouth.

How do you go about checking the vacum, mainly where would I hook the vacum guage.

 

Could be the cops or the connecting springs aren't fully seated.....or a bad plug....

 

I ended up with 2 of 8 NEW plugs being bad.....used the new MC's too.

Start unplugging one at a time. When you unplug and the idle doesn't get worse....there she is...hopefully.

 

When I changed mine I got 1 bad plug out of 8. It threw a CEL and the miss was very noticeable. It could have a stored code in the PCM. Get a computer hooked up to it and see what it says.