Went to the dealership to get a few things checked out.
1st and most importantly was the rough idle I was experiencing. I could notice like a misfire every few seconds, and sugegsted they check the plugs.

I got the truck back, with them telling me "good news, we found a disconnected vacuum line, everything is AOK!"

I thought "awesome" sweet, no more rough idles. I get it back, the rough idle is still there, I pop the hood, and what did they do? They reconnected my boost dump. grr..

 

Pull the stock (assuming here) plugs out and put some NGK TR6's gapped to .040 in there and see if it clears up.

 

Might want to check the IAC valve. I had similar problems until I replaced it.

 

Where's the IAC valve? I know where it is on my buddy's mustang, but not my truck Also, how would I tell if has gone bad? Lightning Boy, thanks for the heads up, I'll be gettign a set of Denso IT22's soon here.

 

Is the engine definitely missing? Mine felt like it had a slight miss and rough idle - turned out to be exhaust vibration transmitted to 2 metal hardpoints where the hangers do not have rubber to dampen the vibrations. Everyone who drove my L thought it had a miss and it took the techs 3 tries to figure out what was wrong.

There is a TSB on this for Lightnings and other F-150's with side-exit pipes. The fix involves adding weights to either side of the exhaust to absorb some of the vibration. Could be a possibility.

 

I had a very noticeable miss around 1000-1200 rpm. I changed the stock plugs (well 7 out of 8 of them) to NGK TR6's gapped at .044. Got rid of 90% of the miss I had, the rest is most likely something other than engine. Runs stronger it seems as well. Hope this helps. Later.

 

thanks for the replies guys, I have my new plugs comin' in soon, so hopefully those will go in (dealer wants $270 to change the plugs) if that doesn't work, I'll see about the TSB.

 

APEX in san jose will change em for $180....

 

Does anyone think I could get the dealer to replace the plugs under warranty. I've had mine in a few times and they can't seem to remedy the rough idle problem. They replaced the IAC valve and checked a few other things...nothing, still there.

I was hoping I could convince them it was the plugs and then supply them with a set of TR5's

What are my chances??

StrikesTwice: Is yours as bad as mine? Mine rattles the dash every time I stop at a light, traffic, ect. I posted about this a week or two ago.

Jon

 

What's an IAC valve?

 

The IAC valve is the Idle Air Control valve. It's the bright tin-colored 'can' attached to the rt. side of the intake adaptor. They can get carboned-up and stck open or shut. They can gey worn too.

Dan

 

Idle air control valve. It lets a certain amount of air go thru the throttle body when the butterfly is closed at an idle. Jim

 

I had the same type of miss after installing 4# pully & NGK BR7 plugs/removed br7 plugs & replaced with NGK tr6 Gap at .040/the miss went away.

 

Lightnin,
no way, sorry man, but mine is no where near as bad as that :-O it's pretty subtle and you have to listen closely, if you look at the RPM needle you can see it barely jumping around, and no it's not the computer switching from lean to rich.
Jason, thanks a lot for the heads up on Apex, I was going to go there next weekend to get a couple pulls on the dyno.