advice needed on a 87 4x4 ranger with a 2.9 and a 5 speed tranny

greaseyfingers · Mar 9, 2009

I have a 87 4x4 ranger, model STX, with a 2.9 engine, which has an aluminum housing 5 speed transmission, that has a square steel inspection plate that is bolted to the bottom of the tranny, with a drain pug in it's center..

I was wondering what the purpose of the switch, sensor, or whatever it is called, which has two wires attached to it, that's threaded and screws into the top of the transmission, just ahead of the 5 speed shifter mounting plate that's bolted to the transmission housing.. I think my transmission is either a mitsubishi fm145, or 146 ??

the switch, I was referring to has threads on it that goes right into the tranny, on top, just a little bit in front of the 5 speed shifter mounting plate..

the wires on mine are mine are broken off, too close to the base, and can't be reattached.. could these wires being broken off, possibly, be the cause of a 2.9 idling weird, sometimes, and the engine running erratic, besides, quite often..

does anyone know what the function of this switch, sensor, or whatever it's purpose is actually for ??

I thought this sensor or switch, or whatever it is, might function as either a neutral switch, or else possibly as some kind of tranny sensing speed sensor, for providing information to the vehicle's computer, for telling it what gear the tranny is in, as it's being driven..

or could it be this switch, for whatever purpose it's function is for, could be for completing a circuit to a light, on the dash panel, that's suppose to let you know when the tranny is in either 4x4, or high or low range, being my owner's manual indicates that there is a light on the dash which is suppose to indicate this..

however mine has never worked.. being the wires are broken off my tranny switch, as I described, could this be the purpose for which it was designed for ??

would like to hear from those who can provide some accurate and knowledable information..

AllanD · Mar 23, 2009

That's a Mitsubishi FM145 transmission.

Your truck is a year too early for an FM146.

That switch with the wire is a Neutral SENSE switch.
It is part of engine management telling the stupid computer
that it's supposed to idle the engine.

AD

greaseyfingers · Mar 23, 2009

being you mentioned that my tranny switch is a Neutral SENSE switch, that is a part of engine management, telling the stupid computer that it's suppose to idle the engine..

that would, definitely, explain why my ranger's 2.9 engine is having inconsistent idling problems, as it can't seem to find it's correct engine idle speed..

would a non functioning mitsubishi tranny fm 145 Neutral SENSE switch, that the engine management system is dependent on for idling, also, cause my ranger's 2.9 engine to run erratic, while being driven at higher rpm's, besides..

AllanD said:
That's a Mitsubishi FM145 transmission.

Your truck is a year too early for an FM146.

That switch with the wire is a Neutral SENSE switch.
It is part of engine management telling the stupid computer
that it's supposed to idle the engine.

AD

Jspafford · Mar 23, 2009

I was always under the impression that switch would cut off fuel to the engine when using compression braking... I know on my truck when the rpm's are up around 3K and I downshift, I can hear the engine get louder like an exhaust brake, and then around 2200rpm, it drops back down to the normal exhaust tone and the truck stops decelerating so fast.

AllanD · Mar 24, 2009

It is closed contacts in neutral and thus cannot have any effect
on "engine braking" or the cutting of the fuel for that purpose.

What it does by being missing is that nothing tells the computer than
the truck isn't in gear so it doesn't know to establish idle as you coast down
And sometimes the engine rpm will dip too low and result in the engine stalling
as you roll up to a stop.

basically as far as the EEC is concerned it's a duplicate of the clutch position switch
(not to be confused with the clutch safety interlock switch to force the operator to depress the clutch pedal to activate the starter.

On a Ford EEC4 system when you close throttle above certain rpm the
engine will drop to "idle level" for a maximum of 1-2seconds after which
the computer is programmed to shut OFF the injectors basically increasing
the engine braking effect.

you can feel this as an additional braking efect after you've been engine braking
for a second or two.

On a 2.3 engine it will allow the engine to run in this mode until
rpm drops to 1700rpm then it will start randomly firing each "batch" of
cylinders as you coast down to 1400rpm where it will gradually increase
the duty cycle of the fuel system to keep the engine from stalling eventually
firing them all to prevent this.

the specific rpm is different for each engine (for obvious reasons)

Jspafford · Mar 24, 2009

AllanD said:
It is closed contacts in neutral and thus cannot have any effect
on "engine braking" or the cutting of the fuel for that purpose.

I figured, although, it is a bit difficult to engine brake with the tranny in neutral?

cocoasranger · Mar 24, 2009

For whatever it's worth, when I swapped an R5OD in place of my A4LD and kept the auto computer, I routed the interlock wires through the neutral sensing switch rather than the clutch pedal switch. The result was I have to have the shifter in neutral to start rather than having the clutch depressed to start. I have not had any problem with the idle when coasting in neutral, or any other problems with the swap.

If there are any problems in doing it this way, I have not seen them yet.

jaymegriffiths · May 21, 2009

I've been told my truck has the same problem. Is the sensor for an R1 the same as fm145, right on top?

AllanD · May 21, 2009

cocoasranger said:
For whatever it's worth, when I swapped an R5OD in place of my A4LD and kept the auto computer, I routed the interlock wires through the neutral sensing switch rather than the clutch pedal switch. The result was I have to have the shifter in neutral to start rather than having the clutch depressed to start. I have not had any problem with the idle when coasting in neutral, or any other problems with the swap.

If there are any problems in doing it this way, I have not seen them yet.

It's easy enough on an '89 to simply swap over the correct transmission wiring harness for a manual transmission....

Two connectors on the inner fender.

And you'll have NO clutch safety aND proper idle control...

Do you honestly think I'm running a clutch interlock switch?
I WANT my truck to lunch forward if you turn the key to start
with the trans in gear.

On Either the FM145 or FM146 the switch is on the top.
On an M5OD-R1 it is on the passenger side opposite from the reverse switch.

AD

Beastly88 · May 23, 2009

My wires on my FM145 are brokes as well and i havent seen a single problems runs just fine .. mine also doesnt have that clutch interlock switch ....come to think of it i dont think theres a single wire that is actually attached to the tranny lol..

advice needed on a 87 4x4 ranger with a 2.9 and a 5 speed tranny

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