It has a rough idle whenever its not fully warmed up and seems to be slightly worse in reverse, it is a 93 4.0 and I just replaced the downpipe o2 sensor
Any help is greatly appreciated

 

Check your IAC, make sure it isn't really dirty, same with the throttle body. Check all your vacuum lines, make sure they aren't cracked or broken. A search on the forum will offer dozens of other potential problems also.

 

I just recently seafomed the tb, sorry but I can't think of what iac stands for at the moment

 

idle air control, it is connected on the left side of your throttle body, off to the side of the TPS

 

Idle Air Control motor, wire plug and 2 torx head screws hold it onto the throttle body. It has an oring and a cone shaped plunger. Controls the air at idle. When it is fouled or failed it will cause rough idle, or even very erratic idle rpm changes. You can unbolt it, spray it with carb cleaner and scrub it gently with your best friends tooth brush. Gently, don't get rammy with the cone. New here is about $60 at Napa.

 

Thanks guys I will check that out tomorrow

 

Quick question, is the iac a 4 prong connector?

 

Anyone know about that^, or is it 3 prong