stwarrior23

So i have a 2005 ford mustang v6 4.0l auto, and been having a rough idle lately, it sort of shakes the car but not bad or anything and as soon as im under way there is nothing wrong and the car runs like a dream.

This happens when i am at a red light in drive, it idles around 550 which i dont like in the first place but dont think could be the problem and it just seems to shake the car a little where my butt vibrates a little and the passenger side seems to be worse, if im at the light for more then 2min it will surge to like 450 and then jump back to 550 and be fine, never stalled yet! i dont hear any hissing sounds or anything and like i said when at 55mph its fine and never loses power so i dont think it could be a vacuum leak but unsure.

So i have cleaned the tb and maf with correct cleaners, replaced spark plugs wires and coil pack inspected my cai everytihng is good. did a ecu reset and nothing seems to be helping maybe for a day or so.

So i have been to many places all giving me different advice, some say alternator or a pulley is loose or a vacuum leak? its kind of like trial and error and im trying to find where everyone is leading to and see what i can do ffrom there?

SO any advice is good advice thanks guys!
and ive been to shops all say it could be a billion things and i dont have time or the money for that!

UltraBlue91'

did you pull codes from your car yet?

stwarrior23

yes there are none

UltraBlue91'

Okay, hmmm check for vacuum leaks. Google "smoke test for vacuum leaks". Have you recently done any new modifications? A surge could also be caused by air to fuel ratio. Your mass air meter could possibly be sending the incorrect voltage to your ecu, causing problems with air/fuel. If you can, check the voltage of your TPS....wouldn't hurt.... with a multi-meter. Bad O2 sensors could be a cause as well. Unfortunately the guys at the shops are right, it could be many different things.

JJHoover

could be a partially clogged fuel injector

UltraBlue91'

That's could be an issue, hey why don't you try seafoaming your car? Just a thought. Not too sure about newer stangs but I'm assuming yours has a manifold absolute pressure sensor. That's a crucial sensor in the cars function and if the voltage is off problems will occur, look up the proper voltage for it on your car and test it if you can.

66and06stangs

I have the EXACT same problem. When my car idles down it sounds terrible. For the most part, my car runs great but does this same behavior.

UltraBlue91'

66and06mustangs,
Have you checked for vacuum leaks?

66and06stangs

I did check for vacuum leaks. Where mine started was when I put a CAI on it and it has been doing it ever since, even though I took it off. AM was good enough to take it back, and initially after taking it off I did not notice a problem. However, I am seeing it occasionally now also. I was about to buy a coil pak and/or some new wires thinking it ignition. I think I emptied 2 cans of starter fluid (I think that or WD40 was what was recommended to find the leak) on the car trying to find one. The CAI had several that I could not seal, hence my sending it back. I am open to any/all suggestions. I loved the sound the CAI gave my car, but should take care of this before any further mods.

66and06stangs

Warrior? Any progress on this? I'm going to look for vacuum leaks again this weekend. I had hoped someone had a spot-on fix but guess not. My car never threw a check engine light either, just an occasional down-rev (what I called it) when coming to a stop.