stutter/hesitation 99 EB

[cbiii]

99 EB 5.4 180k that has always had a miss and poor gas mileage. I swapped plugs initially and after seeing 11.8 mpg i decided to do COPs. After that it ran a bit better initially(~13.4mpg) and then dropped back to 11.8 and eventually developed a sputter. I swapped fuel filter last night and took it out for appx 25 miles. It ran great (minus a slight hesitation which I assume is my trans) and was seeing ~14.6-15mpg. I parked it overnight and went to leave today and I had terrible hesitation, no accceleration and im seeing ~10.7mpg. When i floor it, it just stumbles and never really picks up. No CEL lights or anything after i replaced plugs (~3 months ago)
I rebuilt the vacuum setup coming off of the passenger valve cover with new rubber bits also.
Apparently this is a normal issue for these but ive not seen any solutions.

*also* will not stay idling when started when it has sat and is cold out unless i used heet. (havent checked it with the new filter though)

Granted these numbers are all from the overhead, but it still shows somethings definately wrong.

After new coils,plugs and fuel filter I dont know where to go besides cats/o2s/leaking injector(s)

suggestions?

 

[tmajikman]

99 EB 5.4 that has always had a miss and poor gas mileage. I swapped plugs initially and after seeing 11.8 mpg i decided to do COPs. After that it ran a bit better initially(~13.4mpg) and then dropped back to 11.8 and eventually developed a sputter. I swapped fuel filter last night and took it out for appx 25 miles. It ran great (minus a slight hesitation which I assume is my trans) and was seeing ~14.6-15mpg. I parked it overnight and went to leave today and I had terrible hesitation, no accceleration and im seeing ~10.7mpg. When i floor it, it just stumbles and never really picks up. No CEL lights or anything after i replaced plugs (~3 months ago)
Apparently this is a normal issue for these but ive not seen any solutions.

*also* will not stay idling when started when it has sat and is cold out unless i used heet. (havent checked it with the new filter though)

Granted these numbers are all from the overhead, but it still shows somethings definately wrong.

After new coils,plugs and fuel filter I dont know where to go besides cats/o2s/leaking injector(s)

suggestions?

Take a look at your vacuum hoses that come off the passenger side of the intake, all mine were collapsed, also change the pcv out as well, there is a elbow on the back of the intake that collapses or splits and causes idle issues and poor mileage. Also, get a can of Maf cleaner, pop off you air cleaner, the little sensor after the air cleaner is what you want to spray down.

 

[cbiii]

After driving it last night, I find that when the throttle is held steady at any RPM, it hesistates, sputters and then jumps forward/revs and then falls back into stumbling. constantly.

 

[Jackmldog]

After driving it last night, I find that when the throttle is held steady at any RPM, it hesistates, sputters and then jumps forward/revs and then falls back into stumbling. constantly.

I have the same problem and just replaced all my injdectors. This did not do the trick either. Although, I am getting 17.6 mpg and it runs smoother but it will still start to miss if I have to slam on breaks or go around a sharp curve. Next stop for me is cop and then egr system(cleaning then replacing). But I'll let you know if anything helps mine and you do the same.

 

[cbiii]

took it to a shop and smoked the pcv system. it was pouring out of the EGR. thats next on the list.

 

[cbiii]

removed the EGR and snapped the bolt, had to tap it out, modify the new EGR, put it on, replaced 2 plugs, 2 coils, shuffled some others and its running alot better but still getting shit mileage and hesitation.

 

[cole45]

have you guys figured anything out yet. just got a 99 exy and i am seeing the same problems. i changed engines and at first never had the miss but now i do. i checked codes for a misfire and nothing there. did have a lean code on an o2 sensor but never seen one of them cause the issue i am having. i also see alot of smoke in the exhaust. wondering if these match any of your problems. i also have the problems you guys listed.

 

[cbiii]

I left it alone, as I got my camaro up and running so I couldnt care less about the ford. now that the engines jacked in the camaro (ironic?) im back to the pos expedition. It barely moves under its own power at low speeds, bucks, sputters, etc. As my speed increases, it smooths out. I will be pulling my #104 fuse to see if its transfer case/tranny related tonight and will be doing a fuel pump tomorrow.

 

[cbiii]

Pulling the fuse helped a bit with the terrible (dangerous) acceleration, and picked up a 1.5mpg on the highway, but didnt fix the problem. Swapped the fuel pump the next day and nothing changed. It is also back to running how it did before I pulled the plug, it is slowly getting worse.
done so far-
2 sets of new plugs
new coils (swapped back and forth to confirm theyre ok)
3 different fuel filters
new fuel pump
new air filter
seafoam
disabled auto4wd
new EGR valve
new IAC
new TPS
new vac tree at the throttle body
replaced some vac lines
Hooked it up to a scanner (handheld as well as one at a shop) and no codes, 02 sensors were fine.


help?

 

[cbiii]

new injectors going in this weekend.