Plugs changed at dealer, now rough idle in gear??

[mrlarry24]

Hey guys...new to the site today!

I have an 05 Expy with the 5.4 with 167,000 miles on it.

I had the plugs changed today at the dealer as I know about the problems with the plugs breaking off and wanted it done right. My local mechanic I go to didn't even want to touch it for that reason.

Driving home, I noticed at stop lights the engine was running very rough. If I put it in Park, rough idle goes away as the rpm's head up to about 750 or so.

The Check Engine light hasn't come on yet.

I did replace all coils myself a few months ago as they're easy to do.

I've done a lot of searching on this site: IAC valve, Mass Air Flow Sensor, Vacuum hose leaks and I will do checking on all of that over the next 2 days.

I was just wondering what you thought about it happening AS I WAS DRIVING HOME FROM THE DEALER!!?? Of course, they're closed until Tuesday, but do you think the computer needs to be "flashed"? I unhooked the negative cable on the battery for 30 mins, and still the same thing.

Doesn't seem to be sluggish at all driving though. Only around 500 rpm's and only when in gear.

HELP!

Thanks everyone.

 

[toms89]

Unless it is something simple and obvious I would take it back to the dealer if you had zero issues till you left there.

 

[stamp11127]

The computer doesn't need to be reflashed because of a plug change. Use basic logic, if it wasn't happening before it went into the dealer then it is usually related to the work performed. Not meaning they are at fault, just check what they would have touched during the plug replacement. As Tom said look for the obvious. Something may have been knocked loose or not tightened all the way.

 

[bubbadabulldawg]

Is it a light vibration that you feel in your feet while in gear and your foot is on the brake but goes away when in neutral or in park? If so mine does the same thing and I cannot find where it is coming from! I even went so far as to change out the engine mounts and I also replaced the transmission mount but I still feel it!

 

[KWT2000]

i would take it back, maybe they didnt gap the plugs,

 

[ExpeditionAndy]

mrlarry24,

I'm not sure if you resolved your problem but if you did this might help others.

I talked to my friend John who has a shop in PA and I asked him about this problem. He said that the biggest mistake that people make when they change plugs is they reuse the old wires. He told me that these system are very sensitive to the resistance in the wires and if you reuse an old wire, because of age and corrosion the resistance can be higher, which will cause the coils to fail.

John said that the old wires can gauld to the ends of the old plug and make strong connection, but when you pull them off you break the bond and what's left doesn't make good connection with the new spark plug, which in turn causes higher resistance.

He said it was worth price of changing the wires when you change plugs.

I hope this helps.

 

[steelnewfie]

Try cleaning the head openings where the plugs go in with a wire brush and carb cleaner. The carbon buildups can cause slight arking and low level or apparently random misfires. I'm finding anyway....

 

[Bedrck47]

The last post to this thread before yours was in Sept 2013 do you think they are still checking this thread??