I have an 89 302 which was ideling bad. I replaced the IAC and EGR. both of these helped a little but its still not ideling correctly. Anyhelp would be greatly appreciated.

 

Does "Not idleing correctly" mean the rpms go up and down?
Maybe it stays at the same RPM but misfires?
RPM steady but not where it should be?

 

There are a plethera of items from injectors to fuel pump to sensors that can cause a rough idle. Occaionally, on the older trucks, if there is a noticeable vibration during idling (especially with the A/C or Defrost on), it can be an indication of a cracked motor mount.

 

Did you reset the ECM after installing the IAC?

 

ok well try this, pull off the hoses to the throttle body and get a tooth brush with some carb cleaner and scrub that butterfly...this helped my 302's idling....something easy to do and its not costly...good luck man

 

I finally found the problem but I dont what it is. On the passenger side wheel well there is what looks like a cofee can with two lines running into it. one has vaccum the other dosent. when i take this off it runs perfect. What is it and will it hurt to leave it off.

 

That's a vacuum reservoir. It holds additional vacuum for items like your brakes in situations where manifold vacuum is no longer available.

Disconnect the hoses at the can, and use a vacuum elbow to connect them together, and see if that makes it run better. If it does, replace the vacuum can. If it doesn't, the can is fine, it's the other vacuum line that needs to be inspected.

 

why would that resevior being bad cause it to run bad.