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4.0 rough idle "pulsing/chopping"


k1ll.coyne

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Joined
Sep 10, 2023
Messages
4
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0
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Location
Sacramento, Ca
Vehicle Year
1995
Make / Model
Ford Ranger
Transmission
Manual
I have a 1995 XLT 4.0 RWD Ranger. The other day I was going too fast (~100 MPH) and had to slam on my breaks. After doing so my engine slowly started to die. I was looking in the engine bay and found an open nipple, along with a hose on my frame. After some looking, I found out it was for the DPFE sensor (inner hose missing, further nipple open). I replaced the hose after getting a ride to a store. it didn't fix it. Then I went back and forth to the gas station and put a total of 4 gallons in. I then got starter fluid and it started right up no problem. couldn't fix it. next day we tow it, and it was sitting for 4-5 days before I could work on it. while I was doing my research someone told me it could have been the inertia switch, it was. pushed it back in and starts up. after revving it to charge the battery a bit, when i let it idle, it was kind of like an LS chop. I didn't catch it at first until I got back into the truck and the whole cab was shaking massively, but I also have all OEM suspension (never replaced). It already had a rough idle but nothing like this. The engine was moving as it was full throttle in the bay every time it 'chopped'. It went down to 500 RPM then when it revved itself it revved to 1000 RPM. When I drove it home it wasn't doing that bad, but I still noticed it when I came to a stop.

Is it possible that this could be the IAC, TPS, MAF, vacuum lines, or fuel lines? Or could it also be the ECU? Is it possible I messed with the IAC on accident when re-installing the hose?

Open to questions, just trying to get my daily fixed. I'll try to record what I'm talking about with the chop.
 


Eddo Rogue

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May 18, 2020
Messages
3,987
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Location
Burbank,CA
Vehicle Year
1993
Make / Model
Ranger 4x4
Engine Type
4.0 V6
Engine Size
OHV
Transmission
Manual
2WD / 4WD
4WD
Total Lift
skyjacker front leveling kit
Tire Size
31-10.50R15
My credo
Crossed threads are tight threads.
Could it possibly be your fuel pump is on its way out?

I say this because a sudden jerk will cause my '93 4.0 to do that...its stumbles and jerks then dies completely when the fuse blows. I change the fuse and it starts right up and purrs.

Its the giant green 30amp maxi fuse in the driver side fender box.

I keep a pack of fuses to swap until I have time to poke around and diagnose and fix it.

Also do you have a cam synchro? Mine does and I had replace it once from blowing out and running like crap.
 

franklin2

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Dec 24, 2019
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3,519
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Location
Virginia
Vehicle Year
1984
Make / Model
Bronco II
Transmission
Manual
Videos of "chop"
It seems like when it goes down to idle it does that weird thing then goes back up to 850 RPM

sounds like there is a whistle/wine

http://instagr.am/p/C2CNZXpOZrq/
If you think there is a vacuum leak causing the whistling noise, get your starter fluid out and spray it around and see if you can affect the idle and pinpoint where it may be sucking air. If it sucks in the starter fluid you should be able to tell it.
 

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