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1987 - 1996 F150 & Larger F-Series Trucks 1987 - 1996 Ford F-150, F-250, F-350 and larger pickups - including the 1997 heavy-duty F250/F350+ trucks

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  #1  
Old 01-19-2010, 11:58 PM
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How to know if PCM or wiring harness is bad?

It 95 F250 XL with 351W E40D.

Here issues it run great next day when turn off then start it run ok but when hit pothole or stop. It will idle high plus transmission refused shift 3 or 4 gears it just stay 2 gears until it slipping then BANG in 3 gear like you have nitrous in engine.

When we open hood and wiggle wiring harness from driver fender to engine it kind random it work back normal then few sec it went back high idle.

When we bought that truck first day we fill tank and drove home then around town. Mpg was 15.

Now I can't get 15 mpg anymore without random high idle and transmission won't shift correct. I get 9 or less mpg.


Battery light on dashboard finally gone it was bad connector contact on alternator.
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Currently drive 2000 f350 7.3L XL 4wd auto. mpg vary 15-17.

1999 F250 5.4L 2wd 5.4L auto with over 246K miles. Got used 5.4L with 100K miles. Need find motivation to install 5.4L.
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  #2  
Old 01-20-2010, 01:52 PM
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bump thread
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Sorry for my bad grammar.
Currently drive 2000 f350 7.3L XL 4wd auto. mpg vary 15-17.

1999 F250 5.4L 2wd 5.4L auto with over 246K miles. Got used 5.4L with 100K miles. Need find motivation to install 5.4L.
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  #3  
Old 01-20-2010, 05:23 PM
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Sounds like bad wiring to TPS.
The computer is getting WOT information more than likely.
It will not shift to 3-4 at WOT and the IAC valve would go wide open.
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Old 01-20-2010, 08:45 PM
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That sound could be.

But I just spend think why it do that but it didn't do that when we bought first day.

We wondered that spark plug wires and dist cap we replace with duralast.

Question does duralast cause this issues?

What ohm we need to test spark plug wires? 900 ohm correct?

Throttle body with TPS we try test it say 1.03 but sudden it say 4.03. I hate electric nightmare.

We are plan fix that then sell and get another good f250 or F350.
__________________
Sorry for my bad grammar.
Currently drive 2000 f350 7.3L XL 4wd auto. mpg vary 15-17.

1999 F250 5.4L 2wd 5.4L auto with over 246K miles. Got used 5.4L with 100K miles. Need find motivation to install 5.4L.
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  #5  
Old 01-20-2010, 10:35 PM
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If the PCM really thinks the TPS voltage is 4.0 VDC that is a major cause of most of your issues. Subford nailed it with his theory of what was going on.
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Old 01-21-2010, 02:57 AM
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But why it say 4.0 Volts? bad ground or something? We try add new ground strap from body to alternator that seem improve little.

We been on that truck more than we drive. We put almost 200 miles after that now it all issues.


forgot to add

when it say 4.00 volt when we turn throttle to wide open and 4.00 went to 4.96 or 5.00 for wide open. Sudden it went back to 1.03 volt when we wide open it go 1.98.

Why it jump from 1.03 to 4.00 random? It run fine then sudden it happened again then it disappear then it come back again.
__________________
Sorry for my bad grammar.
Currently drive 2000 f350 7.3L XL 4wd auto. mpg vary 15-17.

1999 F250 5.4L 2wd 5.4L auto with over 246K miles. Got used 5.4L with 100K miles. Need find motivation to install 5.4L.
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  #7  
Old 01-21-2010, 07:08 AM
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You may have a bad TPS but it alone would not do this.
Other things it could be are:
A bad ground wire either in the wiring from the PCM to the TPS or a bad PCM ground wire at the radiator support where the small black wire from the NEG Post of the Battery hooks to the body.
A bad 5 Volt supply in the PCM but not as likely.
Bad pins in the PCM or TPS plugs.
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95 F150 302 4R70W EB EX-CAB
94 F53 460 E4OD COACHMEN SANTARA RV
83 F150 Flare Side 351W AOD
77 F250 351M-2V NP 435/4 Speed 4X4
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Bill K, Kansas Chapter
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Old 01-21-2010, 12:23 PM
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Milwaukee1979F150 Milwaukee1979F150 is offline
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Where PCM would be? We want try add another ground strap to that PCM.
__________________
Sorry for my bad grammar.
Currently drive 2000 f350 7.3L XL 4wd auto. mpg vary 15-17.

1999 F250 5.4L 2wd 5.4L auto with over 246K miles. Got used 5.4L with 100K miles. Need find motivation to install 5.4L.
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  #9  
Old 01-21-2010, 03:53 PM
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A ground strap will not help you.
The ground for the PCM comes in on pins #40 and #60 of its PCM plug.
The PCM is located in the drivers kick panel but you can only get to it from under the hood.
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95 F150 302 4R70W EB EX-CAB
94 F53 460 E4OD COACHMEN SANTARA RV
83 F150 Flare Side 351W AOD
77 F250 351M-2V NP 435/4 Speed 4X4
subford@gmail.com
Bill K, Kansas Chapter
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Old 01-21-2010, 03:53 PM
 
 
 
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