As it says, just bought a new to me 1990 F250 farm truck (this means extremely dirty/mouse crap everywhere), drove it home with minor issues (bad batt cable), high rpms at idle (2K plus)..all in all I was pleased it did as well as it had as it had sat for several years before they decided to sell it off.

After I got it home I started to look deeper into parts I would need to replace and noticed that almost ALL the top emissions stuff (comes off the exhaust pipes) are rotten, to the point not much of its even connected any longer.
The odd thing to me is a lot of it seems to be duplicated and made me wonder how much of this is really needed? there was a H pipe and a T that are more rusted dust than pipe that I need to figure out either to buy or cobble up something that works.

would this stuff effect the idle? thanks before hand on any info ideas

 

pictures are worth a thousand words. could it affect idle, possible. sounds more to me the IAC though. normal thing though, check codes even if light isnt lit because they burn out alot. and again we all like pictures.

 

yeah, need to put it back into place to take some..been going through the forums and have a list of things to get at the junkyard now LOL

 

On a truck this age if the stock cats aren't already gone they should be replaced anyway and that means the whole air injection system serves no purpose what so ever, so unless you have strict emissions tests to pass just delete all of it. And one of the best and most common upgrades is to replace the stock manifolds with headers so if your truck has that crazy manifold system with little tubes into each exhaust port this would be a good way to clean it up. Note that the EGR tube running from the front of the passenger side manifold up to the valve beside the throttlebody is not part of the Air injection system and cannot be deleted without setting codes.

 

yeah, it has the funky tubes off the headers





FINALLY found a part with intact numbers to trace


sure hope the forums resize the photos LOL so found a part with numbers I could read and yes, its a part of the air system, not that i had much luck in finding out much on what it was supposed to do or why this truck looks so much different than 99% of the trucks in the junkyard when I was out looking for the H pipe (8 rows of trucks and only one had the same system)

 

cleaned out a lot of junk hoses and pipes that where all hooked into the mess. looks cleaner (well less junk in the way) and ran it for awhile, sounds better but still has a idle of 1700 rpm. Never messed with EFI before so out of my comfort zone trying to figure some of this out.

Would the egr cause high idle? and can it be cleaned up rather than replaced? Think I'll be picking up a set of injectors from the junk yard and do the cleaning on them (saw a how to on here last night) as well as pricing out 5.0 upper.
Oh are all 5.0's gt40 heads? if not is there a simple/easy way of knowing?
sorry for all the questions

 

Ok after reading lord knows how many threads on here today it seems like if I am planning on a rebuild for the truck picking up a 94+ 5.8 block, 5.0 upper intake and gt40p heads should be on my junkyard list. Plans for the truck are using it to tow a camper from Co to WA and back (My littlest kids out there) so keeping that low end for the mountains is high on the list. any other thoughts or suggestions?

 

Not a bad to do list, but it may not need a rebuild...I'd do a compression/leakdown/blowby test in order to confirm condition.

Your high idle can be a number of things; throttle body sticking slightly open, vacuum leaks (if the truck was a sitter, it has some vac leaks), IAC sticking open

All of these are cheap or free to check, you'll learn a bit about the system, and your idle will undoubtedly go down once you investigate.

 

If there is a break in the tube letting fresh air in yes.

Why? You plan to port the 5.8 lower to match? If not it's a waste of time.

No, Explorer 5.0 only and then only '96 to '97.5.