Can’t pin point
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Junior Member
Joined: Feb 2018
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Can’t pin point
Hey all!
long time reader first time writer... I have 2000 f150 4x4 5.4 225k miles still running good, one thing that is bugging me is when I’m driving and come to complete stop everything is fine, it’s when I release the brake to move my foot to the gas peddle the truck lunges forward quite harshly, so hard it feels as though I have been rear ended... has anybody experienced this?
long time reader first time writer... I have 2000 f150 4x4 5.4 225k miles still running good, one thing that is bugging me is when I’m driving and come to complete stop everything is fine, it’s when I release the brake to move my foot to the gas peddle the truck lunges forward quite harshly, so hard it feels as though I have been rear ended... has anybody experienced this?
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Junior Member
Joined: Feb 2018
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Thanks bluegrass, the idle seems to normal about 800 -1000 rpms I will look into the converter diode, that could be it, if I release the brake slowly the symptoms are no longer noticeable, I was initially thinking it was the rear brakes sticking or something but your suggestion seems quite possible!
Senior Member
Joined: Jul 2004
Posts: 6,200
Likes: 39
From: Easton, Pa.
800 to 1000 is too high with no foot on pedal.
Should be close to 750 hot idle.
Normally on deceleration the IAC closes down and fuel is cut, then the IAC recovers idle close to normal idle as the truck comes to a stop or low speed so there is no stall.
Look at engine temperature. If too cold the idle may go high.
Torque twist of the engine /trans may cause it if the shift linkage is marginal near a Neutral position instead of fully in Drive position at the trans lever.
Good luck.
Should be close to 750 hot idle.
Normally on deceleration the IAC closes down and fuel is cut, then the IAC recovers idle close to normal idle as the truck comes to a stop or low speed so there is no stall.
Look at engine temperature. If too cold the idle may go high.
Torque twist of the engine /trans may cause it if the shift linkage is marginal near a Neutral position instead of fully in Drive position at the trans lever.
Good luck.
Technical Article Contributor
Joined: Jan 2007
Posts: 10,636
Likes: 264
From: Vernon, NY
Normal idle speed of the majority of Ford engines is 750 hot idle, no accessories running (like A/C).
Depending on the balance of the engine components, it should have an AVG variance of 735-775 hot idle
Depending on the balance of the engine components, it should have an AVG variance of 735-775 hot idle
Senior Member
Joined: Jul 2004
Posts: 6,200
Likes: 39
From: Easton, Pa.
The PCM is programmed to keep idle 750 +/- 50 rpm.
'Most' interior air functions run the A/C system so that is a 'normal load' plus the Alternator.
Those loads automatically 'signal' adjust the PCM for idle for 750.
Only exception is cold starts are temperature dependent, raises the idle then comes down in steps as the engine heats.
Good luck.
'Most' interior air functions run the A/C system so that is a 'normal load' plus the Alternator.
Those loads automatically 'signal' adjust the PCM for idle for 750.
Only exception is cold starts are temperature dependent, raises the idle then comes down in steps as the engine heats.
Good luck.