1995 E-250 Puzzler

[drpowell]

No this is not "car talk", my puzzler actually happened today.

For the last several months the automatic transmission would shift very hard. It would hesitate while accelerating from a stop and then hit harder than it should into second gear. I've done all the typical things like check fluid levels, check for burnt smell on the dip stick, flush, and finally have my mechanic look it over, but all to no avail (I'm old enough now that I do not crawl under vehicles unless I really really have to).

Today, we were at a stop light and I looked at the dash saw what I thought was a new problem. Half the dash indicators went out: speedometer (analog), LCD odometer, and turn signals. All of them dead like the key was off. But everything else seemed fine: engine temp, alternator, oil pressure, brake lights, flashers, dome lights, etc. And by the way, the transmission was shifting very rough, an order of magnitude worse than a few minutes before. Shifts were occurring at much higher RPMs than they should. The way it behaved, I was wondering if was going to shift at all then it would shift with a hard hit.

I figured this would be easy, find the fuse that controls the stuff that went out and replace it. I would be a hero to my wife once again. I'm also thinking in the back of my mind, "What electrical circuit would cause the transmission shift worse than before?"

I located the fuse box under the dash by the steering column and started pulling the fuses one at a time to check them out, starting with those that were obvious candidates. Nothing. So I checked the rest of the fuses. Still nothing. Then I decided to turn on the ignition key and use a volt meter on the fuses thinking this would be quicker. Well, my wife says "Hey it's working again." So I jiggled things around thinking there was a loose connection and nothing came back. Obviously a case of a loose connection, or tarnished contacts.

Well, long story short, she drove it home and called me to say that not only is it fixed, but the transmission shifts better than it has in months, "smooth as butter." I must have jiggled at least one more circuit back into place.

Now, I'm a bit worried because I really didn't do anything and I know that a problem that goes away on its own can always come back.

Can anyone tell me what electrical circuit I jiggled in the fuse block to make the automatic transmission work again?

thanks -doug

[BroncoJoe19]

You should have an E4OD trans, the same ones in a full size bronco of the same year.
It is electronically controlled by the PCM.
The PCM uses a few sensors to determine shift points for the trans. including but not limited to:
VSS vehicle speed sensor (on top of the pumpkin in the rear)
TPS Throttle position sensor (attached to the throttle body)
MAP sensor (if you have one. Manifold Absolute Pressure sensor)
MAF sensor (if you don't have a MAP)

You can't hold me to it, but they may all ground out through the PCM.
I believe that the PCM has multiple grounds.

Check and clean your grounds especially those inside the engine compartment, and the ones up under the dash.

Here is a list of grounds for a '92 - '96 bronc

I took a look in my Haynes manual.
They list 10 separate grounds... A-J.

A. Starter mounting bolt
B. Right front of Engine compartment near the battery
C. Lower left front of engine
D. Right front of engine compartment on upper radiator support.
E. Left front of engine compartment Upper radiator support
F. Bottom of cowl panel
G. Rear of left fender apron
H. Behind bottom of right cowl panel
I. Left rear corner of cargo area near rear lamp assembly
J. Under center rear of vehicle on rear cross member.

Ground number and locations in 1990 Bronco EVTM

G100 LH side of Radiator support
G101 RH side of Radiator support
G102 RH side of Radiator support
G103 LH rear side of engine, near knock sensor
G104 LH rear side of engine compartment, near electronic engine control (EEC) module, on the left fender close to the firewall
G105 LH Side of engine
G106 RH fender apron, near voltage regulator
G107 RH fender apron, at starter relay
G108 RH fender apron, at voltage regulator
G109 RH fender apron
G201 LH rear side of I/P (looking at the diagram it is at the bottom of the driver's side dash assembly. Screwed to the bottom edge, just to the left of the steering column. It is the ground for the instrument cluster)
G202 Behind RH cowl panel
G203 RH rear side of radiator support
G204 On steering column
G205 Behind Center of I/P (Dash), near speed control amplifier
G400 LH side of cargo area, near rear light assembly
G401 Below LH side of cargo area, near crossmember
G500 Inside driver's door, near left door speaker

[k2four]

I have the same issue with a 1995 Econoline 250. I replaced the sensor on the rear end and also replaced the speedo. Still not fixed. The speedo jumps around and sometines does not register any speed. The engine will rev extremely high before shifting. The shifting is very abrupt and jerky.

Has anyone figured out how to fix this issue?

[BroncoJoe19]

Sensors that could be bad include
VSS,
TPS,
MAP

also vacuum leak.
You should pull diagnostic codes.
Pull Diagnostic Trouble Codes (DTCs) From your onboard computer.
Your engine and transmission are computer controlled.
The computer uses sensors to tell it a number of different things and it controls actuators that push or pull mechanical levers (kinda). If one or more sensors aren't working properly, the computer goes "blind" and doesn't know what to do. If the computer can "see" but one of the actuators is broken and therefore can't follow the commands of the computer; the engine won't run correctly. The computer is preprogrammed with set values for each of its sensors, and each of its actuators. It will run a self check of all systems, like the space shuttle; it will compare its set value(s) to the value(s) it recieves from its sensors, and actuators. If any sensor or acutator is out of the "normal" range the computer will generate a "code." It will generate some codes on the fly, and others will be stored while you are driving. There is a simple method to "pull codes" out of the computer for one to use for diagnostic purposes.

Earlier versions of On Board Diagnostics OBD 1983-1995 can flash the error code to the dash board and can be pulled in one's driveway without any special tools.
Later versions of On Board Diagnostics OBDII some 1995, and pretty much all 1996 and newer, require one to use a code reader or scanner tool.

Some auto parts stores will scan your engine codes for FREE, you may want to call around. Some will scan OBDII but not the older (prior to 1996) OBD systems.

SO here you go...
How to scan FORD on board Diagnostic Trouble Codes (DTCs) in your driveway
Howto Pull Codes 1983-1995 Broncos, Mustang, F series Trucks, Econolines, 302, 351 and more