98 expedition high idle

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Travistyson1

Active Member
Joined
Feb 16, 2017
Posts
33
Reaction score
1
Location
Seminole florida
Hey guys,
I just picked up a 98 ford expedition 4x4 with the 5.4 triton and a.m. having high idle issues. It idles about 2000 rpm. I have changed all the plugs and coils, new Maf, new IAC and it went from barely running idling high. Wondering what i can do to try and troubleshoot or solve the issue. No codes in the system. All sensors seem to be working properly according to my scan tool,
I'm wondering if the previous p owner perhaps adjusted the throttle screw since it would not stay running without a foot on the gas pedal prior to me getting it and replacing the Maf and other items that was causing the CEL to be on and rough running condition.
 

Bedrck47

Full Access Members
Joined
Jul 4, 2014
Posts
5,641
Reaction score
652
Location
Elizebethtown, PA
You could look into the throttle body to see if the throttle plate fully closes Very possible the screw was adjusted as you suspect. Try turning the screw and keep a count on how many turns you make so you can put it back in case that isn't your problem
 
OP
OP
T

Travistyson1

Active Member
Joined
Feb 16, 2017
Posts
33
Reaction score
1
Location
Seminole florida
Ok so i measured the idle screw and compared it to the other expy i have that came with the deal and it was not the same. Swapped the throttle bodies and idle improved. Still sounds a bit like a lawn mover but it is idling proerly now. Have to change the other 4 coils hopefully that resolves the ping sound. I let it run for a half an hour and no CEL light so back to the old way of finding things. I know some of the sound is the exhaust needs to be replaced. Its in rough shape. Any other thoughs to get it sounding better. It seems to run fine now jist loud like a lawn mower
 

1955moose

Full Access Members
Joined
Nov 23, 2014
Posts
5,981
Reaction score
1,336
First off welcome to the forum. Not always will a check engine light trip. You still could have codes in the computer. Buy, borrow, or go by an auto store, they run codes for free. Exaust leaks make these SUVs run lean, which affect idle. Also get a handle on any vacuum leaks, either by using a smoke machine, or old school, by spraying down all gaskets and hoses in the intake path. Other than that you've done all the other necessary things, like tune up, sensors, electrical repairs. Keep us posted after Exaust and other items get completed. Oh yeah you might want to spell check your posts, I phones flip around what your really trying to say. We know what you mean, just makes it easier to read. Moose


Sent from my iPhone using Tapatalk
 
OP
OP
T

Travistyson1

Active Member
Joined
Feb 16, 2017
Posts
33
Reaction score
1
Location
Seminole florida
I put the scanner on it and still shows no codes however I'm getting 0 volts to my Second Bank rear oxygen sensor the exhaust and rough shape in some areas the muffler itself has a hole in it. I purchase a couple of rear Bank O2 sensors and will be changing those out hopefully today if the weather holds I'm hoping to hold off on doing the exhaust until I have it running good if I can because I prefer not to get the welder out and do it myself but if I replaced all the O2 sensors have the same problem that's kind of where I'm going next I have sprayed down all the tubing to see if I have any vacuum leaks and have replace the ones I found
 

1955moose

Full Access Members
Joined
Nov 23, 2014
Posts
5,981
Reaction score
1,336
Travis you need to figure why you lost your 12 volt signal. One of the other guys here have schematics for your SUV. I looked in my owners book, and didn't see a fuse labeled o2 sensor. I just have an I phone so it's tough for me to bring up items and send. Hang in there one of our other members with electrical schematics should get back to you.


Sent from my iPhone using Tapatalk
 

1955moose

Full Access Members
Joined
Nov 23, 2014
Posts
5,981
Reaction score
1,336
Travis don't know if your 98 is the same as my 2000, but found in the fuse panel under in engine bay the #23 fuse 15 amp is for Hego sensor. You might not only try another fuse, but check both sides for voltage. Hope that helps.


Sent from my iPhone using Tapatalk
 
OP
OP
T

Travistyson1

Active Member
Joined
Feb 16, 2017
Posts
33
Reaction score
1
Location
Seminole florida
Thanks hopefully the weather will clear soon and i can take a look. I still have to change the other 4 coils and plugs. That could be the reason for voltage i guess as well. But i will check that fuse when i get out there.
 

1955moose

Full Access Members
Joined
Nov 23, 2014
Posts
5,981
Reaction score
1,336
Yeah a blown fuse would definitely do it. If you've got your owners book, or maybe download one for your year, just to be sure their the same position fuse.


Sent from my iPhone using Tapatalk
 
OP
OP
T

Travistyson1

Active Member
Joined
Feb 16, 2017
Posts
33
Reaction score
1
Location
Seminole florida
Well in the process of finishing changing the last 3 coils. 2 of the 3 fell apart in my hands. The rear plug came out with the deteriorating coil. Now it appears the previous owner dropped some rubber piecev into one of the plug holes as i have to figure out how to get that out before i can get the spark plug socket in to remove the plug. In addition it appears the threads for the hardest one to get through may be stripped. Its been a rough day to day the least. But hey the oil change went smooth
 

Latest posts

Members online

Forum statistics

Threads
53,396
Posts
500,653
Members
46,812
Latest member
Dcleghorn01
Top