98 Ford Expedition - Rough Idle
 

I have a 98 ford expedition 5.4L w/107K miles. It began to idle roughly, with RPM's fluctuating and stalling at times. Check engine light is on with codes p0171 and p0174 (too lean). I have also had intermitten check engine light come on for p0153 (slow O2 sensor). I've read various info on the internet about Mass Air Flow sensors and IAC motor. Is there a definitive answer for these 171/174 codes?

Welcome
 

Welcome to the site and the Illinois Chapter. I'm sure you will find good advice and suggestions here on your problem. Fairmontman is our chapter tech coordinator, if he sees this he may have your answer. Where are you in Illinois?
Some of us may have a shop recommedation if needed. If you are in the Chicago western suburbs, I can send you to a good repair shop in Darien.

Fastronald - Illinois Chapter Leader

I'm in south elgin.

Iac motors are common problems,especially with higher milage.Sometimes they can be cleaned.You may want to try cleaning the throttle body also.Most parts stores have throttle body cleaner.It may also have a bad o2 sensor if it's throwing that code,but I would start with cleaning the iac and throttle body first.Also make sure the spark plugs and wires are ok. Bob

98 Expedition - Rough Idle Codes 0171 + 0174 Solved!
 

Thanks for your help on this site. A vacuum hose on the passenger side of the engine going back down between the engine and the firewall had a huge hole on the inside of the 90 degree angle going into the engine. The material at the bend in the hose was disintegrated. Replaced the hose and it runs better than it has in a long time.