1991 4.0 Ecm

[BigBlockBill]

I'm almost done with my hodge-podge 89 4.0L/M50D Ranger. It's being built using a 1991 4.0L from a Ranger that was automatic and parts from about 6 other Rangers, Explorers, Sport Tracs, and Navajos. I used the whole harness including the dash(push button 4WD) and chassis harness form the 91 Ranger. I just need to know if I can use the auto ECM form the 91 with my 5spd or do I need to locate a MT ECM? What year ECMs will work with my harness? Thanks in advance, Bill

[swamprat]

You can use the auto ECM. You will need to jump your clutch switch

[BigBlockBill]

The harness from the 91 had the clutch switch connector. I just pulled the dummy plug and hooked it up. Thanks for the reply.

[AllanD]

While your truck will run wand drive with an automatic trans ECM (though "PCM" is the prefered acronym) there will be some issues.

the first being relatively minor...
The computer will set codes for TCC (torque converter clutch solenoid)
and for the 3-4shift solenoid as it's signals to your right arm are being ignored when you install a manual transmission.

the other part is less noticable to the driver until he feels it in his wallet...
at the fuel pump.

the 4.0 a/t PCM uses a different idle/coast strategy than the m/t computer.

The M/T PCM will cut ALL injector pulses any time the TPS signals a throttle closed condition when engine rpm is greater than 1500-1700rpm and will only fire the injectors intermittently below that down toabout 1100rpm.
This is to improve engine braking response AND save fuel.

Running an a/t PCM then switching to a M/T PCM will usually net you
atleast 1mpg gain in mileage, sometimes as much as 2.5mpg, though
this greatly variable depending on vehicle gearing, driving style and
your local terrain.

Hilly country
Numerically larger gears
the driver's tendency to engine brake
will all increase the differences.

what computers will work with your engine and wiring?
91&92 M/T computers,
'93-up will NOT work (calibrated for different injectors and dual HEGO's)

and there is no such thing as a 1990 4.0 M/T computer.
1990's were all Automatics.

You want one? I have a 1992 5sp "X2X2" computer sitting here.

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[BigBlockBill]

Thanks for the reply Allan, the info is greatly appreciated. How much are you looking to get out of the PCM? Shipping would be to 26505.