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F250 Deceleration Stall #4582723
11/23/17 10:19 AM
11/23/17 10:19 AM
Joined: Apr 2003
Posts: 2,023
Cincinnati
dkryan Offline OP
dkryan  Offline OP
Joined: Apr 2003
Posts: 2,023
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 doesnt have to chase more parts?

Thanks.


2014 Nissan Altima 2.5 SL
Pennzoil Ultra 0w-20
Fram Ultra

2005 Toyota Highlander
Amsoil 5w-30 SSO
Fram Ultra filter
Re: F250 Deceleration Stall [Re: dkryan] #4582731
11/23/17 10:28 AM
11/23/17 10:28 AM
Joined: Oct 2012
Posts: 2,108
Northern Ontario, Canada
Danno Offline
Danno  Offline
Joined: Oct 2012
Posts: 2,108
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.


2016 Sorento SX V6 AWD
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2010 Mazda 3 2.0L
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Re: F250 Deceleration Stall [Re: dkryan] #4582746
11/23/17 10:42 AM
11/23/17 10:42 AM
Joined: Mar 2017
Posts: 117
northwest pa
justintendo Offline
justintendo  Offline
Joined: Mar 2017
Posts: 117
northwest pa
does the truck have any idle problems? sometimes the IAC solenoid gets dirty/stuck..(idle air control)


2013 escape 2.0 awd
2008 fusion 2.3 mtx
1996 f150 4.9 2wd mtx
1999 kaw zrx 1100
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Re: F250 Deceleration Stall [Re: dkryan] #4582773
11/23/17 11:14 AM
11/23/17 11:14 AM
Joined: Nov 2017
Posts: 683
South Carolina
eyeofthetiger Offline
eyeofthetiger  Offline
Joined: Nov 2017
Posts: 683
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.

Last edited by eyeofthetiger; 11/23/17 11:15 AM.

2017 Ford Fiesta 1.0T - Valvoline SynPower 5W-20, Motorcraft FL910S
1988 GMC K1500 4.3/700R4 - Supertech 15W-40, Fram TG3980
1986 Ford Ranger 2.0 - uhh
Re: F250 Deceleration Stall [Re: Danno] #4582814
11/23/17 11:58 AM
11/23/17 11:58 AM
Joined: Oct 2008
Posts: 967
Iowa
Nyquist Offline
Nyquist  Offline
Joined: Oct 2008
Posts: 967
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.


2015 Chevy Traverse 3.6L (LLT) Mobil 1 5w30 w/ Fram Ultra
2017 Chevy Cruze Hatchback 1.4L (LE2) Mobil 1 5w30 w/ Wix
Re: F250 Deceleration Stall [Re: dkryan] #4582859
11/23/17 12:44 PM
11/23/17 12:44 PM
Joined: Jun 2003
Posts: 17,348
Deplorable in apple valley, ca
Chris142 Online content
Chris142  Online Content
Joined: Jun 2003
Posts: 17,348
Deplorable in apple valley, ca
This is usually caused by the idle air motor.


02 Wrangler durablend 10w40
87 F250 traveler 15w40
04 Tahoe super-s 10w30
Z400 castrol T 10w40
Can am maveric edge 5w40
57 case tractor 15w40
Re: F250 Deceleration Stall [Re: dkryan] #4583015
11/23/17 03:57 PM
11/23/17 03:57 PM
Joined: Apr 2016
Posts: 842
KS
FordBroncoVWJeta Offline
FordBroncoVWJeta  Offline
Joined: Apr 2016
Posts: 842
KS
Gas filter.


17 Volkswagen Jetta 1.4T
15 Honda CRV 2.4
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01 Pontiac Sunfire 2.2
Re: F250 Deceleration Stall [Re: dkryan] #4583091
11/23/17 06:09 PM
11/23/17 06:09 PM
Joined: Aug 2008
Posts: 18,408
Ontario, Canada
StevieC Online content
StevieC  Online Content
Joined: Aug 2008
Posts: 18,408
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.




Last edited by StevieC; 11/23/17 06:12 PM.

'18 Highlander - AMSOIL SS 0w20 / ATF / Severe Gear
'06 Santa Fe - 535,000km AMSOIL SS 0w30 / ATF (R.I.P)
Re: F250 Deceleration Stall [Re: dkryan] #4584694
11/25/17 05:42 PM
11/25/17 05:42 PM
Joined: Apr 2003
Posts: 2,023
Cincinnati
dkryan Offline OP
dkryan  Offline OP
Joined: Apr 2003
Posts: 2,023
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.


2014 Nissan Altima 2.5 SL
Pennzoil Ultra 0w-20
Fram Ultra

2005 Toyota Highlander
Amsoil 5w-30 SSO
Fram Ultra filter

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