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2005 350 Mag high idle

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conny737

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"My 2005 350 Mag MPI high idle

"My 2005 350 Mag MPI high idle at times.
The RPM meter normally indicates around 800 rpm with engine idling (a little bit high maybe, as the book states 600 rpm, but the instrument might not be calibrated correctly). After running for a while, idle won´t drop below 1000 rpm, which makes gear shift very noisy. Most likely not very tender to the gear box either.
If I turn the engine off and restarts it, idle is normal. But the high idle problem reappears after running for a while at higher rpm´s.

The engine handbook states that “MPI idle rpm can not be adjusted”. Any suggestions?"
 
IAC failing? Computer needs r

IAC failing? Computer needs reflashed? My truck computer needed reflashed due to high idle.
 
IAC is the "Idle Air Contr

IAC is the "Idle Air Control" btw... a GM version of a little stepper motor that modulates the flow of air to the engine. The more air the faster it idles. If the valve is sticky it may perform like you state.

Also - look for vacuum leaks. Do not attempt do adjust your base idle like you would on a carb.
 
"Thanks both of You for advice

"Thanks both of You for advice! Sounds as the first thing to have a look at is the IAC, as the problem disappears (for a while) after engine restart. Is it an easy task to check if the valve is sticky?
I guess a reflash would have to be performed by a authorised mechanic."
 
"Check the throttle cable adju

"Check the throttle cable adjustment first, but it sounds like it's the IAC (which is actually a pulse width modulated valve made by FORD, not a GM stepper motor)."
 
"Thanks, will do that next wee

"Thanks, will do that next weekend. An IAC problem sounds expensive, so I just hope it is the throttle cable..."
 
"75 bucks for a marine spare p

"75 bucks for a marine spare part! Well, that´s good news. Always thought their pricelist started at 100..

Anyway, checked the throttle cable today. Looked ok, next step will be to check the IAC...hmm.. better call a mechanic for that. But on the other hand, 75 bucks is what he charges per hour. And he probably has his schedule full until mid August.
Is the IAC easy to remove/install?

/Conny"
 
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