Hey guys i just installed an accufab plenum with a 70mm TB on a 04 Mustang GT and when everything is put in place Also i put a spacer in between the plenum and manifold.. the car revs pretty high at neutral from 1500 RPM to 2000 RPM!! but when i shift to first it goes down back to normal!! Also sometimes it idles very high when i just turn the car on!! Now the TPS was set to 1 to .980 volts (according to the other mustang forums thats how it should be set) then i heard that the IAC has to be clean.. but the car is new so it should be clean to begin with.. Im also hearing that it takes a day or two for the computer to learn new items on the car? is that true?? Can anyone help me here!! its very frustrating!!
Having problems with Idle .. after putting in Accufab Plenum
- Thread starter madstyle1
- Start date
take the spacer off. Ive heard that if you use a spacer and the plenum, it will cause an idle issue. Also check for vacuum leaks, someone else on here experienced this problem and it was a leak
Vacuum leak
Installed the 75mm Accufab T/B and Plenum on my 03 GT about 2 weeks ago. Initially when sitting in neutral it would hang at about 1250 rpm after having blipped the throttle then settle down after about 5 secs. or so to a normal idle. Would also do this when coming to a stop. Read some good info here about vacuum lines so sealed all the line with high temp RTV and made sure I went through the proper procedure for resetting the computer. Everything is good now. Look in the section in your owners manual about changing the battery. It has the computer reset procedure and be sure you leave the negative lead from your battery off for at leat 45min. before doing it. When it resets you will see your guage needles go fully to the right, then back to normal. If you don't see this you didn't leave the battery unhooked for long enough. After you see this, follow the procedure in the manual.
Installed the 75mm Accufab T/B and Plenum on my 03 GT about 2 weeks ago. Initially when sitting in neutral it would hang at about 1250 rpm after having blipped the throttle then settle down after about 5 secs. or so to a normal idle. Would also do this when coming to a stop. Read some good info here about vacuum lines so sealed all the line with high temp RTV and made sure I went through the proper procedure for resetting the computer. Everything is good now. Look in the section in your owners manual about changing the battery. It has the computer reset procedure and be sure you leave the negative lead from your battery off for at leat 45min. before doing it. When it resets you will see your guage needles go fully to the right, then back to normal. If you don't see this you didn't leave the battery unhooked for long enough. After you see this, follow the procedure in the manual.
twogts4us
15 Year Member
Get rid of the plenum spacer!!!!
When you are removing it, disconnect the neg bat cable. When you're done, reconnect. Turn the key on and watch for all the gauges to peg then fall back down to zero. Then start the car. Mine still took a week of driving to completely settle down, but it wasn't idling at 1500 - 2000! (That's being caused by that spacer!) It was more like 1000 - 1200 for a couple secs, but now its more or less back to normal.
When you are removing it, disconnect the neg bat cable. When you're done, reconnect. Turn the key on and watch for all the gauges to peg then fall back down to zero. Then start the car. Mine still took a week of driving to completely settle down, but it wasn't idling at 1500 - 2000! (That's being caused by that spacer!) It was more like 1000 - 1200 for a couple secs, but now its more or less back to normal.
stangman
15 Year Member
the spacer is the problem, take it off. the plenum has a built in spacer, so there is no need for another 
StangLou
Active Member
No spacer needed man. After my install the car would hang at around 1300rpm when coming to a stop or when I would blip the throttle. It took around a week or so but it stopped doing it altogether. Just reset your eec or give it some time. It will drop on its own
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