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91 ranger 4.0l with 92 explorer ecm


Bodie1991/4.0

Member
Firefighter
Joined
Nov 1, 2023
Messages
21
City
Washington
Vehicle Year
1991
Transmission
Manual
Hey everybody my name is Bodie and I’ve been driving rangers since I was 16 my first truck was a rusted out 92 2wd 2.3 kinda butchered that truck and feel pretty bad about beating on it as much as I did but I digress my new project I’m working on I’ve been flying solo for about two years just trying to work out kinks and I’m stumped thus joining trs I have a lot done to the truck so I’ll have to explain further if anybody is willing to help my now truck is a 91 4.0 factory 4x4 I’ve sas’d it and replaced the ecm with a 92 explorer ecm because in all of my 21 years of wisdom I left the battery plugged in with the key on while welding on the truck🤦‍♂️ so what I got going on is I can’t get it to rev above 3000 rpm and I’ve replaced the tps, map, iacv, air intake temp, coolant temp, and checked all of these things prior to replacing most of which were fine just dirty so those went on the shelf. Back to the list I’ve also replaced the fuel filter and tested for pressure all good there as well I’ve supplied pin 30 with 5v from pin 26 and the rear axle I put in it came with a wss not sure on condition but it out of a dodge so I don’t assume it works. Lastly I put the nss on three switches so I can turn it on and off for testing nothing has seemed to work any help is appreciated thank you for reading
 
You can't rev it past 3000 rpm because the ecm you used is for an automatic transmission and it thinks the transmission is in park
 
Are you trying to rev it beyond 3000 while sitting still or while driving? The part you're calling an ecm is a processor and I've seen those limit unloaded RPM's. Gm vehicles had ecms.
 
Last edited:
Are you trying t rev it beyond 3000 while sitting still or while driving? The part you're calling an ecm is a processor and I've seen those limit unloaded RPM's. Gm vehicles had ecms.
While driving it doesn’t rev over 3000
 
I also should add it’s a electric transfer case that does shift in and out of 4hi and 4lo and the shift on the fly does work till I think around 15 mph don’t know for sure I like to stop prior to shifting the transfer case
 
Just took it out for a short drive it also lurches bad with light throttle but wide open seems ok
 
Is it generating any codes? Were the symptoms present with the original processor? Did they gradually get worse or suddenly appear? Have you double checked all the grounds?
I've seen Duraspark modules create the same symptoms as restricted fuel flow, your TFI might do the same thing.
 
Is it generating any codes? Were the symptoms present with the original processor? Did they gradually get worse or suddenly appear? Have you double checked all the grounds?
I've seen Duraspark modules create the same symptoms as restricted fuel flow, your TFI might do the same thing.
Don’t know for sure what tfi acronym is and yes it’s giving a code for map sensor and purge solinoid test while not running symptoms not originally there. And only starts with the new processor old one just cranks and obd1 won’t respond
 
No TFI on a 4.0. It's EDIS. Crank signal goes to EDIS module and PCM. Without them both working at least somewhat you wouldn't start.
 
are you sure you are not using a bank fire harness with a sefi pcm?
 
are you sure you are not using a bank fire harness with a sefi pcm?
Idk from what I can tell I got the truck with original or at least new old stock ford ecm it went bad so I got another from a rolled manual explorer that ran good. As for the wiring it’s all factory still. How could I tell if any had been swapped or changed?
 

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