2004 4.6 fast idle

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MPBGT

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I have a 2004 4.6 expedition 2wd that seems to stay on fast idle longer than it should. I would assume this is an iac issue, but the info on the 4.6 iac seems to be conflicting. Does the 2004 have a Normal iac that can be cleaned or replaced? Any other thoughts on the fast idle staying active longer. It runs at 1,000 to 1,100 rpms and then eventually drops to 700 ish.
Any help would be appreciated
 

Yupster Dog

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Not throwing any codes? How does your air filter look? Check and clean the MAF sensor.
 
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MPBGT

MPBGT

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Not throwing any codes? How does your air filter look? Check and clean the MAF sensor.


No codes, update: I cleaned the iac and replaced the TPS. No change. Also I cleaned the mass air sensor.
I would think vac leak, but after it clicks off high idle it settles in at like7/800 rpms and is fine.
 

Hamfisted

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Do you have a scanner that'll read live data ? What's it reporting the engine temperature at ? Possibly a bad or failing engine temp sensor ?
 

Yupster Dog

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I had the wire harness for the MAF mess up on me and had to replace. Try starting the truck and moving the wire harnesses around to see if it makes a difference.
Definitely check for vacuum leaks. start on the passenger side valve cover check PCV hoses. You could also smoke the intake (couple threads on here how to. check @1955moose threads for a build your own smoker)
And if you can get your hands on a scanner with live data like Ham said that would really help getting you closer to the problem.
 

the bus

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I had a problem with a new iac and had to do a hard reset of computer to clear learned memory. Disconnect battery terminals and then connect the terminals together with some light gauge wire for 15 minutes. Then reconnect battery. Start from park, the let idle in neutral for 3 minutes and go to 1st and let idle for 3 minutes and finally go for an easy 2 mile drive to get it to go through all gears and get it to kick down once time towards the end. Oh yeah clean your throttle body out. You are getting extra air from somewhere. Then it would need to be smoked for vac leaks. Live data would help too to see maf rate etc. Check your maf wiring / clip like moose said.
 
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