what is this and will it cause my engine to surge I replaced the TPS, o2 sensor, CTS, brain box and still have no luck, when i unpluged this it stopped surging and just idled real high so im wondering if i replaced this would it fix the cold idle problem, please help me !!!!!!

*MOD EDIT* made the pic not so rediculously huge... *MOD EDIT*

 

IAC. Try cleaning it first before replacin it.

 

what does IAC stand for ??

 

idle adjustment control

 

thank you for the help do you think this could be causing the surge in rpms when engine is cold? or am i chasing my tail ? when i say surge its up and down not just high

 

maybe,

try cleaning it .
put it out and clean it with carb.cleaner.
look out for the spring and pin.
Tom
:hail:

 

tryed cleaning it and nothing, so i put a new one in and still have the same problem, i just dont know what to do next...

 

what are the specs of the engine?

 

FYI:
https://www.thirdgen.org/techbb2/sho...hreadid=271931

 

305 TBI 5.0L 1991 all stock, except for all the new parts ive added in the last couple days

 

give the ecm some error codes?

 

no codes, my father just took it for a drive to give it time to get some, should i have disconnected battery after installing all the new sensors?

 

Never a bad idea

 

I believe it stands for Idle AIR control. But either works.

 

OK Here is a list of all I have done to try in fix this problem

new brain(computer) same chip
TPS
CTS
O2 sensor
air temp sensor
idle controler
fuel filter
new cap and rotor
new plugs and wires

after replacing the plugs and wires and cap and rotor it runs alot better, but its still rough idle at start-up and has a hesitation when you give it gas from a stoplight or even if i am already moving there is hesitation.........im running out of ideas here

 

Maybe ignition coil or possibly the pickup coil???

 

When you pulled out the IAC did you clean inside the chamber? Sometimes it gets gummed up and won't allow the plunger full travel. Just a thought, been there before.

 

check your fuel pressure

 

ok i had this exact same problem and i believe it is the idle air control valve!
to test it use the little code key you get at autozone for free or use a paperclip and bridge the a and b teminal on your aldl port... i think is a and b i forget but the are right next to each other then turn on the car to the on position, do not crank it.
then wait a few seconds and the iac should close all the way.
then go out under the hood while the car is still on and unplug the iac connector
then crank it up and run it a bit. and see if it still surges.
i bought the holley 670 unit and i have replaced the iac 3 times and it still gets screwy. if you read on the little pamplet that comes with the replacement iac it says if it surges like that to run it hard over 2000 rpm's for a few minutes and it should stop. mine still does it occasionally. the only reason i have mine plugged up right now is because its winter time. i will unplug it again in the spring, also do a search on the aldl plug so you can see what it looks like. it is under the dash under the steering column.

 

yea i know how to run the test and check for error codes i will try that and see if it works, i am having a mechanic put some injector cleaner throuth the injectors they run it directly through the tubes so it is concentrsted and see if thats causing any problems

 

Its Fixed !!!! heres what I did i had a mech shoot some fuel injection treatment directly into the fuel lines to clean the injectors and now it runs like a champ, thank you so much for all the help on this forum and i hope this helps someone else who is having the same problem