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#4582723 - 11/23/17 09:19 AM F250 Deceleration Stall
dkryan Offline


Registered: 04/11/03
Posts: 2022
Loc: Cincinnati
My friend has a 1995 F250 with 115k miles on it. It has the big V8 in it (7.3?).

When decelerating, the engine wants to stall at 15 mph. He replaced the throttle position sensor and the vacuum regulator solenoid.

No luck.

He connected a vacuum gauge from the vacuum regulator solenoid to the EGR valve. The engine is pulling 5 to 15 inches of vacuum at 15 mph, i.e., the vacuum solenoid is opening.

Any ideas so he doesn’t have to “chase more parts?”

Thanks.
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#4582731 - 11/23/17 09:28 AM Re: F250 Deceleration Stall [Re: dkryan]
Danno Offline


Registered: 10/07/12
Posts: 1991
Loc: Northern Ontario, Canada
Long shot, but does the transmission have a lock up torque convertor? Might not be unlocking at low speeds - or sticking - causing a drop in revs.
Again, a long shot.
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#4582746 - 11/23/17 09:42 AM Re: F250 Deceleration Stall [Re: dkryan]
justintendo Offline


Registered: 03/04/17
Posts: 101
Loc: northwest pa
does the truck have any idle problems? sometimes the IAC solenoid gets dirty/stuck..(idle air control)
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#4582773 - 11/23/17 10:14 AM Re: F250 Deceleration Stall [Re: dkryan]
eyeofthetiger Offline


Registered: 11/18/17
Posts: 683
Loc: South Carolina
I assume this is the 7.5 (460) gas, and not the 7.3 diesel.
Is there a CEL so you can pull codes? Does it drive normally under other conditions?

Like justnintendo said, an easy thing to check is the IAC. Remove it, scrape any carbon out and clean it with throttle body or carb cleaner. You may also disconnect the battery for a minute to reset the computer.

Otherwise, start with the basics, like an old fashioned tune-up. Check the base timing, idle speed, vacuum at idle, fuel pressure, ignition system, maybe even the air filter.
There is a base idle adjustment screw on the throttle body that you aren't supposed to adjust because it is not going to fix the problem, but sometimes it is useful.

If you have reason to suspect the EGR, you can check the function of the EGR valve with the engine idling. Connect a vacuum pump to the EGR valve and manually apply vacuum. You should be able to see the valve move, and the engine will start running rough or stall.
If you don't have a pump, you can use a vacuum line straight to the intake manifold, but you must keep it plugged until you stick it onto the EGR valve.


Edited by eyeofthetiger (11/23/17 10:15 AM)
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#4582814 - 11/23/17 10:58 AM Re: F250 Deceleration Stall [Re: Danno]
Nyquist Offline


Registered: 10/24/08
Posts: 967
Loc: Iowa
Originally Posted By: Danno
Long shot, but does the transmission have a lock up torque convertor? Might not be unlocking at low speeds - or sticking - causing a drop in revs.
Again, a long shot.


My vote goes to check this out. I've seen this a lot with some past automatic transmissions.

An easy way to check this would be to put it in neutral when coming up to a stop.
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#4582859 - 11/23/17 11:44 AM Re: F250 Deceleration Stall [Re: dkryan]
Chris142 Offline


Registered: 06/05/03
Posts: 16820
Loc: Deplorable in apple valley, ca
This is usually caused by the idle air motor.
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#4583015 - 11/23/17 02:57 PM Re: F250 Deceleration Stall [Re: dkryan]
FordBroncoVWJeta Offline


Registered: 04/16/16
Posts: 768
Loc: KS
Gas filter.
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#4583091 - 11/23/17 05:09 PM Re: F250 Deceleration Stall [Re: dkryan]
StevieC Offline


Registered: 08/21/08
Posts: 17116
Loc: Ontario, Canada
I would check things in this order..


1) Throttle Position Sensor (Replaced)
2) Transmission not unlocking. (Shift to Neutral before 15mph)
3) Idle Control Motor sticking
4) Vehicle Speed Sensor not functioning properly letting the ECU know the vehicle is slowing down.
5) Some vehicle ECU's will turn off the injectors when you are coasting and it might not be turning them back on just before coming to a stop.
you can watch this on a Scan Gauge or Scan Tool.
6) Watch fuel pressure as you are slowing down if possible.





Edited by StevieC (11/23/17 05:12 PM)
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#4584694 - 11/25/17 04:42 PM Re: F250 Deceleration Stall [Re: dkryan]
dkryan Offline


Registered: 04/11/03
Posts: 2022
Loc: Cincinnati
UPDATE:

The engine is a 7.5L gasoline engine.

All “tune-up” parts were replaced, including the gas filter. The spark plugs are not budging, absent drilling them out.

And my friend tried the “shift into neutral” at 20 mph to check the torque converter. Several times. No joy.

Based on advice on this thread, he replaced the idle air control valve.

Apparently, that solved the issue.

He has run the truck the past two days since replacing the IACV and the deceleration issue has not occurred.

Both he and I extend our thanks to those BITOGERs who responded.
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