sk8erpunk56

i have an 86 that i got that was speed density. i did a mass air swap, and 24 lb sensors and injectors. did a gt40 intake swap and a bbk 76 mm throttle body swap. after i did the mass air swap i was having alot of problems with the the erratic idle. the hoses were all original, so i replaced all the vac hoses. i also replaced the map sensor, later to find out i could have just plugged the whole with a screw. i also replaced the iac and still no results. the only thing i havent tried was either a new ecu or new air sensor cause i baught the parts used. the only thing that has been bogling my mind, is that if i disconnect the map sensor hose and let it take air the idle levels out alot more. and wont stall when you mash the clutch to stop. but if i plug the hose or plug it into the map sensor the idle goes crazy. i have checked every seal and every hose for a leak but i really dont think that is the issue, cause when i purpusfully make a leak it levels out. i am a little lost here and am not sure where to go. i have more projects lined up that depend on my keeping a steady idle.

393strokervert

have you hooked up a vacuum gauge to it? check to see if it is pulling steady @ idle. also, where is your air filter? are you using a cone filter on the end of the mass air? my stang is newer but I had a similar problem with the idle. does the mass air still have the screen on it? my problem was the cone filter was causing turbulence so the mass air had problems reading the air going thru it. might sound crazy but I took 1 layer of a t-shirt &tightly clamped it in between the filter & the mass air & that fixed my problem.when the air went through the fabric it stabilized the air flow, thus allowing the sensor to read it properly. just a thought. good luck

sk8erpunk56

well it is a fender mounted cold air, cone filter. i tried rotating the mass air sensor to see if it was getting a bad read beacause of the bend, but it still just did the samething. i will try that when i get home. i am trying to get as much info as i can now cause i am stationed in germany right now and fixin to move, and i need to be able to drive from new york to kansas. and with all this **** i aint going to be able to do it. but i am not sure if restricting the airflow would work. cause like i said if i disconnect the map sensor and let is suck in air it idles alot better and makes is more drivable. but i will def let my bro know back home and try that and let you know what happens.

393strokervert

the t-shirt trick doesn't really restrict the air as much as it just smooths the airflow somewhat allowing for a better read. mine was getting too much gas (due to the turbulence ,it was basically telling the ecm that the engine was getting more air than it actually was & therefore giving it too much fuel) which sounds like what yours is doing, thus the vacuum leak"disconnected map hose" would give it more air to go with the fuel. mine actually runs better all around with the fabric in there. I have a cone filter on the end of the mass air. my mods are in my sig & the car puts down around 330hp/400tq to the wheels & that is with the puny e7's & baby cam.

sk8erpunk56

man i was talking to a guy in my platoon and he thought that might be the prob even tho he never heard of it. that just brightened up my day. i will have to admit this is my first build. and i am still trying to figure it out. i think i should have started with something other than an 86 cause it has been nothing but probs.

393strokervert

well I hope for you that it is something simple like that. I am somewhat new to the mustang performance world & to the forums myself but there are alot of great gearheads on here that know there stuff. if you haven't already, try running a few searches in here & you will probably find some better answers to your problem.
Good luck on your stang, God Bless & Thanks for serving our country the U.S.A.