I've started noticing a dipping idle when stopped primary while in drive.(very rarely it will do the same while in park) I have recently replaced the plugs wires and coil and then to try and fix the dipping idle I replaced the idle air conrol valve. The IAC valve seemed to help but I just noticed it dipping again while at a red light. It's not throwing any codes, does anyone have any suggestions to try next? I'm thinking next thing to try is cleaning the throttlebody?

 

Yep. I would definitely clean throttle body

 

Well I've cleaned the tb, cleaned the Mass airflow sensor and then did a seafoam intake cleaning and replaced throttle position sensor. Thought it was doing great and then started dipping again.

What's next? Any help is appreciated.

 

Do you know if the 2005 4.2l has an IAC valve or not, I can't find the damn thing?

 

Follow your throttle cables to the throttle body, then look for something that looks like those in the link below, mounted on the TB, probably straddling the blade. It's a mechanism that bypasses the throttle blade so it is mounted on the TB itself.

p.s. edit - actually it might not have one. I just found a video where you can see where it should be but it's not there. Might be that Ford went to the electronic TB in 2005. I time stamped the video to where you can see the shape of the holes for the IACV but they don't seem to be open for use. At 42 seconds.


https://www.rockauto.com/en/catalog/...ac)+valve,6072

https://www.rockauto.com/en/moreinfo...t=6072&jsn=615

 

Found another 2005 video where you can see the IACV passage that is not used and the mounting spot for the IACV. 2005 and after is a really weird time for the 4.2. Ford completely redesigned the intake manifold then discontinued the 4.2 just a few years later. The IACV thing looks like they even changed their minds in the middle of the redesign. Instead of building new injection molds they just modified the new molds by blocking off the IACV port. Weird that they left the bolt holes though and put bolts in them. Maybe that was easier than modifying that part of the mold. Looks very "hacked".

Could also be that they put the IACV on the TB and just used the old IACV passage. It still has a gasket on it.

 

Found another. That TB looks electronic. Probably no cables to follow and no IACV anyway. Last post here, I'm going to collect these videos in another thread, just for the future.