[bobs184]

Well, my years of good luck with this car have finally come to an end. All of a sudden, I've got a problem.

The idle dips while sitting at a stop light, not quite enough to stall, but close. Then it bounces back up to normal. It does this every 3-4 seconds. Just started, after making no changes whatsoever. I checked for leaks in the CAI / intake and see nothing. Does this sound like a bad alternator or could be a spark plug / wire that has gone bad? The car has 76,000 miles and the plugs haven't been changed for a very long time.

It is much worse in drive / reverse (I'm guessing because the idle sits a little lower there). In park / neutral, the idle dips are still noticeable though and I can hear pops in the exhaust that are new as of the past couple days.

No check engine light. Driving at any speed, I notice no problem whatsoever. It's only when I come to a stop at a light or stop sign that this happens.

Thanks for the help!

 

[amustangrocks]

sounds like its (past) time for routine maint. plugs, FUEL FILTER, air filter, pcv valve, clean the tb would be a good start.

 

[stlbzmustang]

Do a tune up and clean the IAC. mine use to do that i cleaned it and no problems.

 

[bobs184]

Air filter is 3 months old, I clean the MAF and throttle body almost monthly. I'm thinking plugs at this point. Could it be the wires or just one or more of the plugs themselves?

 

[amustangrocks]

Air filter is 3 months old, I clean the MAF and throttle body almost monthly. I'm thinking plugs at this point. Could it be the wires or just one or more of the plugs themselves?

i do plugs every 30,000max. wires are most likely ok still. when did you do the fuel filter last?

 

[TexasBlownV8]

Plugs will make the car run like that. A failing alternator would be totally different symptoms.

Check the plugs on the driver side first, those are the ones that usually show wear first. My stock plugs on the driver side were crap after 25k miles.

 

[bobs184]

Thanks for the info. Fuel-filter is up-to-date. I will go ahead and get new plugs in the next few days, and will you keep you posted on here.

 

[bobs184]

One more question if you don't mind...I just want to make sure. The car drives normal and I can't feel the shutters when driving, or coasting. But, acceleration still feels perfectly normal too. Just as fast, and no difference in exhaust tone when accelerating. It's just when sitting. Does that still make sense for a failing spark plug?

THANK YOU!

 

[bobs184]

One more question, just to make sure.

I don't feel the shuttering while coasting or driving at a normal highway speed, which is understandable.

But I wanted to check on this...acceleration still feels perfectly normal. Just as fast, and no change in exhaust tone (no pops either).

Does this make sense for a failing spark plug to only be felt while sitting at idle?

THANK YOU!

 

[stlbzmustang]

Clean your IAC...

 

[bobs184]

Taking it in tomorrow. Gonna start with IAC before anything else. Thanks

 

[05mystang]

There is no IAC on the 05+. As texasblown said I would rule out the alternator it would affect a lot more than just idle. Start with the plugs, I believe they are supposed to be gapped somewhere around .050-.055, although I would have to check.

 

[stlbzmustang]

http://www.allfordmustangs.com/foru...ing-hanging-idle-2006-mustang-gt-iac-tps.html

Im not sure if this will help but check out post #9

 

[bobs184]

Reset the tune today. Flashed it back to stock, then flashed the 87 Performance tune I typically run. No difference with the problem. It's still there.

Took it to NTB (who I made an appointment with and and described the symptoms), and when I got there they wouldn't even look at it and told me to take it to Ford for tests.

Could it be a throttle sensor perhaps? Computer tests just sound very expensive! Could something have went wrong with my tune just like that? Help please!

 

[trynot24getthis]

I feel like I have the same problem, except I have no tunes and no engine add ons.

I know its not the motor mounts and I just changed the spark plug cables. My plugs are about a year old (~10k miles) and I have taken them out and checked the gap about three times now. I need a new serpentine belt, but the tensioner and belt seem find. The plugs don't seem like the have oil on them I don't think I have a head problem. I just put di-electric grease on the plugs so that hopefully if it is a ground issue they can conduct better. Not sure if that helped or not. Just did it today

Maybe the coils? Do these things have coils? or are they just electronic distributors?

If I figure it out I'll let you know. Are you running oem plugs?

 

[longalan2]

sounds like a bad maf or coil pack.

 

[nascar_red]

Factory gap for the plugs is .054. I also have a question, what is an IAC. Your problem seems to be the throttle position sensor. If it was plugs they would be showing symptoms continuously, idling, or highway speed. Please keep us informed.

 

[bobs184]

Here's my update. This is crazy, but please hear me out!!

Took the car to Ford this morning at 7:30 AM. The symptoms were there on the way to the dealer (shutter at idle, almost stalling). I had to keep my foot on the gas to keep the idle around 1,000 so it would remain stable.

Here we are at 5:00 PM, and I have the car home. The dealer had 3 people drive the car a combined 30 miles or so and they simply could not get the problem to happen. (IT HAS HAPPENED EACH AND EVERY TIME I'VE DRIVEN THE CAR IN THE PAST 3 WEEKS). Said they had people drive it hard, full throttle, and also sit with it in gear and there was nothing.

I agree, it's simply not doing it now. Neutral idle is smooth, and drive idle is smooth while just sitting. WHAT ON EARTH?

I've only been driving it soft and gentle since this problem developed. Is it remotely possible that having it driven hard and full throttle a few times fixed something? Perhaps having the throttle plate completely open cleared something out of there?

I know it sounds crazy, but I myself can't believe that the car is running perfectly today. Nothing was done to it (other than have mechanincs drive it and apparently beat it up on the road).

Thank you for any insight again!

 

[akdoggie]

I'm going with the TB being dirty on the back side and causing the idle air passage to be partially blocked. They can look clean from the outside out when looking into the bore, but you most likely will find that there is a bunch of crap hidden there causing your problem. It seems to be a normal maintenance item. You have to remove the 4 bolts that hold the TB to the manifold and disconnect the TPS, but it's certainly easy enough for most people to do with ease. I'd bet they blew some of the crap out of the bore, but it will come back. Clean the TB. JMO.

 

[trynot24getthis]

my cat went out today.