Is this an IAC problem?
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Joined: Dec 2006
Posts: 24
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From: Wichita, KS
Is this an IAC problem?
My 2000 Expedition 5.4L starts fine with a high idle after the start at about 1200rmp. After about 5-10 sec it drops to about 1k. It stays this way until it gets warm and then will drop to about 600-700 rpm. The problem now it that at stops it will search for idle from about 400rpm to 800rpm after sitting for about 15sec at the light. Sometimes it will just die completely after the 15 sec without searching. I pulled the Expy up to a curb and let off the brake and it began searching with the brake off. It will search for idle in Park and Neutral but the rpm swings are not as wild and it usually not die.
I have searched the threads for this problem and the suggestion was to check for vacuum leaks and to clean the Idle Air Controller (IAC). I checked for leaks, even the PCV valve elbow at the back of the throttle body. I pulled off the IAC and cleaned it with Simple Green. It looked great inside after the cleaning. I got all of the junk out of the seal seat. I replaced the IAC and took it for a test drive to be disappointed again. After the engine was warmed up, it started searching for idle at stops.
I am going to buy a new IAC to make sure that there is nothing wrong with the one I have. I am leaning toward a bad IAC because I would think a hidden vacuum leak would be apparent even when the engine is cold.
Does anyone have any other suggestions?
I have searched the threads for this problem and the suggestion was to check for vacuum leaks and to clean the Idle Air Controller (IAC). I checked for leaks, even the PCV valve elbow at the back of the throttle body. I pulled off the IAC and cleaned it with Simple Green. It looked great inside after the cleaning. I got all of the junk out of the seal seat. I replaced the IAC and took it for a test drive to be disappointed again. After the engine was warmed up, it started searching for idle at stops.
I am going to buy a new IAC to make sure that there is nothing wrong with the one I have. I am leaning toward a bad IAC because I would think a hidden vacuum leak would be apparent even when the engine is cold.
Does anyone have any other suggestions?
Senior Member
Joined: Jan 2006
Posts: 2,835
Likes: 0
From: Vienna, Georgia
Originally Posted by DHoot
My 2000 Expedition 5.4L starts fine with a high idle after the start at about 1200rmp. After about 5-10 sec it drops to about 1k. It stays this way until it gets warm and then will drop to about 600-700 rpm. The problem now it that at stops it will search for idle from about 400rpm to 800rpm after sitting for about 15sec at the light. Sometimes it will just die completely after the 15 sec without searching. I pulled the Expy up to a curb and let off the brake and it began searching with the brake off. It will search for idle in Park and Neutral but the rpm swings are not as wild and it usually not die.
I have searched the threads for this problem and the suggestion was to check for vacuum leaks and to clean the Idle Air Controller (IAC). I checked for leaks, even the PCV valve elbow at the back of the throttle body. I pulled off the IAC and cleaned it with Simple Green. It looked great inside after the cleaning. I got all of the junk out of the seal seat. I replaced the IAC and took it for a test drive to be disappointed again. After the engine was warmed up, it started searching for idle at stops.
I am going to buy a new IAC to make sure that there is nothing wrong with the one I have. I am leaning toward a bad IAC because I would think a hidden vacuum leak would be apparent even when the engine is cold.
Does anyone have any other suggestions?
I have searched the threads for this problem and the suggestion was to check for vacuum leaks and to clean the Idle Air Controller (IAC). I checked for leaks, even the PCV valve elbow at the back of the throttle body. I pulled off the IAC and cleaned it with Simple Green. It looked great inside after the cleaning. I got all of the junk out of the seal seat. I replaced the IAC and took it for a test drive to be disappointed again. After the engine was warmed up, it started searching for idle at stops.
I am going to buy a new IAC to make sure that there is nothing wrong with the one I have. I am leaning toward a bad IAC because I would think a hidden vacuum leak would be apparent even when the engine is cold.
Does anyone have any other suggestions?
Technical Article Contributor
Joined: Dec 2004
Posts: 382
Likes: 0
From: Lake in the Hills,IL
Dhoot-
I am having the exact same problem you listed. I let mine sit and search for idle (in Drive, with the brake applied) in a parking lot for 15 minutes the other day hoping it would throw a CEL, so I could pull the code. Still nothing. Does anyone out there have a "diagram" of all the vacuum lines for a basic 5.4,or can point us in the right direction? If you find something let me know, and vice versa.
I am having the exact same problem you listed. I let mine sit and search for idle (in Drive, with the brake applied) in a parking lot for 15 minutes the other day hoping it would throw a CEL, so I could pull the code. Still nothing. Does anyone out there have a "diagram" of all the vacuum lines for a basic 5.4,or can point us in the right direction? If you find something let me know, and vice versa.
