shaners90lxhatch

Well then, the code either has nothing to do with your surge (which I think it does) or, whatever could contribute to a high idle and a surge is your possible cause........ again, like a vacuum leak. 600-800RPM is a broad range. This thing should idle at ~525 with the IAC disconnected. Raise your idle a bit underhood, unplug the IACand then slowly return the throttle to the resting position. If you are higher than 525, you have a vac leak or something

92cobra

well im doing the first thing you said as of disconnecting the negative part of the battery and letting it sit for 15mins, in 3mins i will go reconnect it. Where is the iac located, i will unplug it if i can get a pic or a discription.

90Lxstanger

code # 12- cylinder no. 3&4 low-cylinder balance test-
this is what i found a #12 is... doesnt seem right at all though.....wierd

92cobra

i disconnected the battery for 15mins, put it back on started the car and the idle was the exact same right about 800 in park.

shaners90lxhatch

90lxstanger - that is definately not the wrong code description.
If the KAM reset did not drop your idle, the TP closed throttle voltage is accurate.....
Either way man, there are several things that could give you both a surge at cruise and a code 12. I think you are on the right track checking your base idle. The IAC is a big cylindrical looking thing that is bolted to the side of your throttle body. This is where the air enters the engine. There is a two wire plug on it. Disconnect this following the procedure in my previous post to check your base idle. Oh, by the way. Your stock tachometer is known to be several hundred RPM off the actual engine speed. Obviously this will not make things easier for you but should not keep you from figuring this out.

92cobra

i appreciate the post and deffinately will check in the morning, but again to state the problem. When the car is warm, if i hit WOT i can not pass 3000 rpms without violent surging.

92cobra

adder i see your reading this, please suggest something lol, im dieing.

Ive done a tune up, fuel filter, egr, o2 senors *both* and i have no idea, please shed light on this.

AdderMk2

has you car done this the entire time youve owned it, or is it a recent problem?

92cobra

the entire time ive owned it, i bought it from the dealership, then realized the problem. It doesnt happen if the cars cold, but it does if its warm.

AdderMk2

I have a list of questions for you, but heres just a few!
Does your car still have factory cats? https://mustangforums.com/m_864112/tm.htm
Have you tested your TPS for any electrical "dead spots"?
The fact that your car gives you problems when it warms up, leads me to believe you might be having TFI module issues. But im stumped as to why it would only occur past 3k rpms.