2005 mustang gt idle and acceleration problem
 

Hey guys I'm new to this forum I have a 2005 mustang gt manual with about 86,xxx miles on it I've only had it for about 4 months . I've been running around in circles like an idiot sense I got the car trying to figure out the problems I'm having but I just can't seem to figure it out . I'm a full time technician have been sense I was 16 so wen I found the car with the idle problem and acceleration problem for 3,400 i jumped on it real quick thinking I would have it fixed in no time. But that's not the case and it hurts my pride a little to ask for help but I'm ready to get this car on the road.
The problem I'm having is very temperamental sometimes I'll fire it up and its fine I can run down the road with no problem at all.
So wen it is acting up at idle the engine is knocking, rpms bounce from around 400- 1200 , it is gasping air like a human breathing I can watch my air filter move like your chest dose wen you take a breath then exhale, and finaly I have a weird throttle response if I just smoothly push the pedal to the floor sputters and pops but and push the pedal just a little bit and let go nothing happens until I let my foot out and it revs perfectly fine but that is 1-2 seconds after my foot is already off of the pedal. It also will not communicate with my scan tool or tuner and goes into some sort of limp mode where none of the gauges show anything except for the tack and speedo and the traction control turns off

Wen I got the car the smart junction box had corrosion so I cleaned that ,I've already replaced all 4 o2 sensors, replaced throttle body, replaced maf sensor, all coils and spark plugs were replaced by the last owner trying to fix the problem , checked for vacuum leaks , exhaust leaks ,and tried a throttle relearn. At this point I don't know where to go next so any help is greatly appreciated.

Sorry for such a long message I just wanted to be thuro because I know how hard it is to diagnose from a distance

Here ya go:
http://iihs.net/fsm/?d=9&f=Step%203-...m%20Charts.pdf

You'll want Chart 1, seems to me...

Now, as far as the pinpoint tests... well, they're 'here', but not:
http://iihs.net/fsm/?d=11

Seems it only goes up to 'H', and that's an issue because there's HC, HY... and others that aren't there. And no, you can't use the 2011+ one, it's not there either.

You might want to subscribe to something that can get you the actual Ford Mustang shop manual if this one doesn't work for you. But the Chart maybe can help you in finding the issue in a 'these are the parts in question to look at' issue.

At the end, it might be worth having a dealership/person with a scan tool with diagnostics look into this. Not knocking your abilities, but sometimes it's ok to just yell uncle or something rather than beat one's head against a spiked brick wall...

Hope that helps. Welcome to the Forums! :wave:

Thank you I will look through that wen I get off of work hopefully itll give me a good direction to shoot in next . As far as other forms do you know any that may help?