engine idle dips when coming to a stop
Thread Starter
|
New User
Joined: Nov 2010
Posts: 1
Likes: 0
engine idle dips when coming to a stop
My 2001 F150 Supercab, 5.4l, 4x4 engine idle dips to 300rpm as I approach a stop sign and then comes back up to 700rpm when stopped. If I do the same thing without the overdrive engaged, there is no problem. Is this a transmission/torque converter problem or something smaller? Is there a solenoid that I need to change? I have already tried the Idle Air Control Valve replacement, it has not helped. Any feedback or experience is appreciated!
Thanks!
Thanks!
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
I would bet the speed sensing is missing.
Here is what is supposed to happen on deceleration.
The TPS is at rest and speed slowdown rate is sensed.
The PCM takes this info and closes the IAC to a low opening enough not to stall the engine and injection is shut down to prevent fuel to the cylinders as a fuel saving event.
If the IAC is not commaned to open back up enough and keep the idle within limit, you will have the effect you see.
If you keep a bit of foot throttle on and it helps, you can about bank on it being a speed sense issue.
Good luck.
Here is what is supposed to happen on deceleration.
The TPS is at rest and speed slowdown rate is sensed.
The PCM takes this info and closes the IAC to a low opening enough not to stall the engine and injection is shut down to prevent fuel to the cylinders as a fuel saving event.
If the IAC is not commaned to open back up enough and keep the idle within limit, you will have the effect you see.
If you keep a bit of foot throttle on and it helps, you can about bank on it being a speed sense issue.
Good luck.
Thread
Thread Starter
Forum
Replies
Last Post
Harabec
1987 - 1996 F150 & Larger F-Series Trucks
19
Feb 17, 2021 10:43 AM
fyrmn681
1994.5 - 1997 7.3L Power Stroke Diesel
16
May 14, 2011 07:53 AM
