Should I be worried? (Sorry, it's a little bit of a read.)
 

Good morning everyone.
About two months ago, my 2005 GT (Manual Trans) would idle kind of weirdly when I would stop. The Tach wouldn’t do any noticeable movement, but I could feel the engine really doing some odd running. It almost was like it was getting ready to stall out, but then it would catch itself. The only other symptom it was having was when I would be traveling at hi-way speeds, and I would accelerate to pass, or just to have a little momentary fun, it seemed like I had no power available at all. I would consistently have to drop to 4th, sometimes even 3rd, to get enough power to do any hi-way accelerating.

This went on for about 2 weeks, until finally my Check Engine light came on. I took it in, and the end result was that two spark plugs had "gone bad" and had been replaced, along with a bad ignition coil. This was about 3-4 weeks ago.

Now, as of about 2-3 days ago, I'm noticing the same thing happening, as far as weird idling at stops. Its doing (although not always, and not as often as before) the same thing that it was doing before. But now, I'm seeing the Tach definitely doing some moving. At a dead stop, my usual idle is 750RPM. Now I'm seeing it mainly still at 750, but frequently slowly lowering down to 500, and on more than several occasions, nosedive to 250, almost stalling the car out, but then shoot up to 1,000 then rest back down to 750 again. The other thing I've noticed with my idle is that when I'm coming up on a red light, say at about 500ft or so out, I'll put it in neutral and just coast up to a stop. What I'm seeing now when I do that, is that my RPM's will sometimes be up at 1,300 - 1,500 and stay above 1,000 until the light turns green again.

I've "tested" the hi-way acceleration issue, and I don't think I can trust myself for results, because sometimes it seems that it's obviously happening again, other times it seems fine, where as the first time, the hi-way acceleration problem was always consistent.

So, should I be worried/concerned? Keep going until I get a Check Engine light again (assuming I'll get one at all), or be pro-active and take it in to the Dealer?

As always, thanks for your help and input.

Now, Im not very versed on the 05's, but that sounds like an Idle Air control valve issue like we have on the 99-04's a lot. If your car has one of these, try checking it (cleaning it out with brake cleaner). Now, how many miles does your car have, because this usually doesnt happen until the car gets about 40-50k miles on it, but thats exactly what it sounds like. Also, do you have any mods and not a tune? Maybe that could be some of it. Need a little more info.

Same thing I was going to suggest.. IAC is a bitch, period. I also had a TPS going bad once (throttle positioning sensor) and it caused my RPMs to hang badly when I would press in the clutch or whatever. It finally went out and then acted like I had no gears at all lol

Don't know if it has one or not, but I'll see if I can find out. When you say "try checking it" what should I be looking for? As for milage, it has just barely over 11k on it, and has no mods at all, nor has it been re-tuned.

you are DEFINATELY having some problems. Make sure that you check all of the vaccum and breather hoses to make sure that they are hooked up perfect. Check to see if something is unplugged. If your car is still stock and you know for sure that everything is hooked up and working then I dont know what to tell you. Then i would just take it to the dealer because your definately having problems. Clean the MAF sensor and the IAC sensor. Run some fuel injector cleaner through it.

Don't check anything.....take that thing back to the dealership and make them check it......That's what the 3 year 36,000 warranty is for :beerchug:

You say that the spark plugs went bad?

You probably arent running on all yer cylinders...

Check the plugs...

Its weird that you are having these problem on a brand new car... so I would just take it to the dealer for that warentee like JJTgiants said...

after all... ya did pay for that service...

and yes... Be worried...

you may end up having to drive their rental car for awhile like I have. Ive been in 3 rentals and I put them all to my test. I flogged out a V6 Taurus, Ford Focus, and a Nice 06 F150 w a 5.4:devil2: That F150 was badass and I want one.

I really dont mind taking my car to the dealer cause I just know that theylle put me in some cheap car and I just go crazy having fun in it. Better not damage the car though......:o

That definitely is a vacuum leak or IAC issue. The spark plugs that 'went bad' were most likely just fuel fouled and not lighting the fuel/air mixture. The tech probably saw the fouling and decided to change the coil pack too.

The wifes 06 does that sometimes too.No lights yet though hmmmmmmmmm.

agree with above...don't do anything BUT drive it to the dealer. Try to get it there while it's acting up. You mess with it, Ford CAN and MAY say YOU f"ed it up!!!DEALER DEALER DEALER.If you don't like the one you got the car from take it to another....

IT could be all of those listed above or the following. Maybe for some reason your spark plug wires are F'ed up....but take it to a dealer. There is no reason for something like this to happen to your car. BTW...your car is misfiring..that is what is causing your RPM gauge to jump.

there are no spark plug wires on these cars. each plug has it's own coil sitting right on top of it.

really?

wow... I didnt know that... I can't keep up w/ this new automotive tech...

Had the same problem with my 06 GT. It's a bad coil. The dealership won't replace them all just the bad one. I had the number 5 cylinder go bad then waited a week for the part to come in then had the number 1 cylinder go bad. But needless to say, haven't had a problem since.

Wait a Minute
 

actually thats not true... by law a dealer can only reject warranty service if the aftermarket part was - is - and only could be the problem, anything else he has to fix - don't take sh!t of dealers they will try to screw you. But, wut do i know I am just an attorney