Bought a 93 w/ 4.9L a few weeks ago. the truck is very nice and just what i have been waiting to find. Little to no rust, the body and interior is in good shape but it just had some mechanical issues. The motor was just replaced by ford about 20k miles ago and i decided to have the trans rebuilt so everything would be reliable. Since it's purchase it was running bad. I started replaceing things one buy one.

Every sensor was replaced even though none had thrown any codes.
I gave it a complete tune up w/every fluid and filter.
checked pressures, vacuum, timing,everything.

It is running almost like a new truck.....almost. It still idles a little rough and the RPM's seem a little high. I would normally just drive it and accept the fact it's old and runs like it. I decided to dig in to it thinking it had to be a small leak somewere in the intake tract. Gaskets are cheap so i decided to pull the manifolds off and replace them. I found two things that might be of some use.

When i installed the new egr i was too lazy to walk to the garage and get a torque wrench. The base of the egr that mounts to the manifold has a small crack running clean through it. It's only a cast base and i geuss i overtorqued it. theres one leak.
The second thing was the lower manifold. The mounting bolts are shared by the intake and exhaust. There are just tabs on the top of each manifold and the bolt runs in and pinchs both to the head. The manifold again is just cast. Every tab on the lower manifold was cracked and obviously no getting a good seal. The tabs were all still in place and with a little oil build up i couldn't see it until i removed the bolts.
I checked for leaks multiple times till i was blue in the face. but i think i found my problem.
I see there are alot of questions and trucks with idle running issues so just maybe this will help someone.

 

Thanks for the ideas! I know my EGR valve is cracked, never thought to post up about it though, didnt know it was a common problem

 

I have never had that happen before and i have owned alot of fords and alot of new egr valves. I wouldn't have seen it except the gasket was still new and hadn't stuck to the egr valve yet.
The cracked intake i had seen in another post before and i thouhgt the guy was nuts. Now that i'm looking at the manifold and design i bet theres alot of rough running trucks with those broken manifold tabs. See i shouldn't have doubted the senior poster.

 

hmmm... sounds good... i may have to check that out, my truck doesn't run very rough, could just be the worn out mounts, but its worth looking at now that I think i'm keeping it for a while

 

The symtoms were so slight. idle was a little rough but couldn't tell by listening to the exhaust. The iac would work fine but as it warmed up idle would rise to about 900rpm and then when at op temp it would steady at around 850rpm in park. in drive around 800rpm. just alittle high. It was just bothering me that i couldn't track it down. Now the question is. Where can i buy a new lower? ford will be too expensive. There are no more u pull it's around here and the yards won't seperate the intake so the best price i could get was 300. Even then will the replacement eventually crack again? I don't put much faith in cast a aluminum. Any one know of a place that sells lowers for a reasonable $

 

happened on my donor motor, what happened to it though was the yardguy that was pulling it was in a hurry as it was cold and snowy out in the yard and he had everything unbolted, but when you pull these motors out you have to turn it so it comes out from under the cowl area. what he did was let it come straight out had it chained to the intake and let the forklift make it come out, breaking all the tabs on the intake. i was very po'e when i got it apart in the garage and had to pull pieces of intake out of the valves through the ports! luckily i had the old one from the truck so i used that and took the opportunity to replace the valve cover casket that was seeping anyway. check with whoever did your work, if they did replace the valve cover gasket and over torqued the bolts it will break the tabs aswell. dont give up though, once you get that running right it will run damn near forever. heck even broken they will run, mine went 100 miles without oilpressure, knocking the whole time, 2 rods threw the block and one through the pan, and got me home.

 

oh and before i get yelled at for driving it like that :P i did purchase the truck knowing that it was knocking and with no oil pressure, i just figured id get as close to home as possible before i had to call the tow truck!