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2.9 bucking under load, high/low idle


DangaRanger

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Location
VA
Vehicle Year
1990
Make / Model
Ranger XLT
Engine Type
2.9 V6
Transmission
Manual
2WD / 4WD
4WD
1990 2.9 manual, truck is bucking under load at any speed and in any gear, I have replaced Map sensor, TPS, IAC to no luck.... I unplugged TPS and truck no longer bucks and runs like new.... what am I missing here ?
 


franklin2

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Bronco II
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Take it for a spin and get it fully warmed up. Bring it back home and while it's idling in the driveway, unplug the IAC plug. The idle should slow but not stall out. If it stalls out, turn the idle stop screw in till the engine idles about 400-500 rpm. If when you pull the plug the idle stays the same, it's too fast. Turn it down. This will put your throttle position idle voltage more in line, and make the dashpot feature start working again. See if that helps it.
 

DangaRanger

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Joined
Mar 1, 2021
Messages
4
Reaction score
0
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Location
VA
Vehicle Year
1990
Make / Model
Ranger XLT
Engine Type
2.9 V6
Transmission
Manual
2WD / 4WD
4WD
Take it for a spin and get it fully warmed up. Bring it back home and while it's idling in the driveway, unplug the IAC plug. The idle should slow but not stall out. If it stalls out, turn the idle stop screw in till the engine idles about 400-500 rpm. If when you pull the plug the idle stays the same, it's too fast. Turn it down. This will put your throttle position idle voltage more in line, and make the dashpot feature start working again. See if that helps it.
Will have to give this a try Wednesday, I tried this at first to test the IAC before I replaced it and it passed but had a new one already so I replaced it, I have a new ignition control module coming I will try that as well and see if there is any issues as for it is only happening once the engine reaches operating temps.
 

DangaRanger

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Messages
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Location
VA
Vehicle Year
1990
Make / Model
Ranger XLT
Engine Type
2.9 V6
Transmission
Manual
2WD / 4WD
4WD
UPDATE, new ignition control module fixed all issues. Truck is running fine even with A/C on under load.
 

DangaRanger

New Member
Joined
Mar 1, 2021
Messages
4
Reaction score
0
Points
1
Location
VA
Vehicle Year
1990
Make / Model
Ranger XLT
Engine Type
2.9 V6
Transmission
Manual
2WD / 4WD
4WD
Franklin2 I appreciate the input you gave me as well.
 

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