E4OD/Tach Problems
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Logistics Pro
Joined: Feb 2011
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From: Townsend, MT
E4OD/Tach Problems
Recently the tach (or so I think) on my '90 has been acting up. When I jump in it and go, all is well for 15 or 20 minutes. Then the tachometer starts jumping back and forth, sometimes goes dead and then starts to jump back and forth. When in neutral, the tach works perfectly fine.
I replaced the tach sensor thinking it was bad. Nothing changed. I swapped in a known good used sensor and nothing changed.
When the tach is acting up, it causes the tranny to shuttle betwixt gears and lock/unlock the torque converter just as rapidly as the tach needle jumps around.
Today I didn't even get 15 minutes. As soon as I started it and put it in gear, the tach went haywire - so I unplugged it.
I have worked on a '91 that had a bad tach sensor before. The tranny worked just like normal without lockup - this is why I just unplugged my sensor.
The thing is, unplugging my tach sensor didn't change anything. Now the torque converter stays unlocked, but it jumps through the gears exactly like it did before.
And to add to it all, the tranny has less than 10K miles on it.
What do you all think is wrong?
TCM/TCU?
Tranny?
I tested the throttle position sensor and it is right in spec.
I am at a loss.
I replaced the tach sensor thinking it was bad. Nothing changed. I swapped in a known good used sensor and nothing changed.
When the tach is acting up, it causes the tranny to shuttle betwixt gears and lock/unlock the torque converter just as rapidly as the tach needle jumps around.
Today I didn't even get 15 minutes. As soon as I started it and put it in gear, the tach went haywire - so I unplugged it.
I have worked on a '91 that had a bad tach sensor before. The tranny worked just like normal without lockup - this is why I just unplugged my sensor.
The thing is, unplugging my tach sensor didn't change anything. Now the torque converter stays unlocked, but it jumps through the gears exactly like it did before.
And to add to it all, the tranny has less than 10K miles on it.
What do you all think is wrong?
TCM/TCU?
Tranny?
I tested the throttle position sensor and it is right in spec.
I am at a loss.
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Logistics Pro
Joined: Feb 2011
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From: Townsend, MT
Also, if I push the O/D Off button, it won't keep it out of O/D. The light stays for a few seconds until it try to go into O/D (which it does). When it is in O/D for a few seconds, the button doesn't do anything.
Before when it would work for the first few minutes, the O/D Off worked just like normal until everything else went to hell.
Before when it would work for the first few minutes, the O/D Off worked just like normal until everything else went to hell.
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Logistics Pro
Joined: Feb 2011
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From: Townsend, MT
I have also thought of this. I have poked and probed until my hands turned blue to no avail. And I don't think it has anything to do with the tach as it acts the same way with the tach unplugged.
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Logistics Pro
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From: Townsend, MT
I have recently been through my whole fuse box chasing a bad light switch.
What relays to I check? Do I even have any relays beside the EEC?
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Logistics Pro
Joined: Feb 2011
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From: Townsend, MT
I have done a bunch more testing. I have swapped in a known good TCM = no change. My tps tests good but I unplugged it just for kicks = no change. I unplugged the TCM = big change.
It only works in 2nd and 4th, but I have no hunting going on. That is the only thing that I can do to keep the transmission from hunting.
I am stumped and need to know where to look. Solenoid pack? Is there another relay besides the EEC?
It only works in 2nd and 4th, but I have no hunting going on. That is the only thing that I can do to keep the transmission from hunting.
I am stumped and need to know where to look. Solenoid pack? Is there another relay besides the EEC?
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Logistics Pro
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From: Townsend, MT
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Frmr Ford Trans Engr
Joined: Aug 1999
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From: SE Florida
I still think this is the problem.
What does that mean? Does the wire show electrical continuity from the connector to the TCM? Is it shorted to ground or to power?
This shows that the problem is NOT inside the transmission. It's hunting because the TCM is telling it to do so. Something is sending the TCM bad info. I think it's the wiring to the tach sensor. It could be that the TCM is losing power and frequently resetting. That could happen from a bad EEC relay.
I have done a bunch more testing. I have swapped in a known good TCM = no change. My tps tests good but I unplugged it just for kicks = no change. I unplugged the TCM = big change.
It only works in 2nd and 4th, but I have no hunting going on. That is the only thing that I can do to keep the transmission from hunting.
It only works in 2nd and 4th, but I have no hunting going on. That is the only thing that I can do to keep the transmission from hunting.
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Logistics Pro
Joined: Feb 2011
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From: Townsend, MT
I still think this is the problem.
What does that mean? Does the wire show electrical continuity from the connector to the TCM? Is it shorted to ground or to power?
This shows that the problem is NOT inside the transmission. It's hunting because the TCM is telling it to do so. Something is sending the TCM bad info. I think it's the wiring to the tach sensor. It could be that the TCM is losing power and frequently resetting. That could happen from a bad EEC relay.
What does that mean? Does the wire show electrical continuity from the connector to the TCM? Is it shorted to ground or to power?
This shows that the problem is NOT inside the transmission. It's hunting because the TCM is telling it to do so. Something is sending the TCM bad info. I think it's the wiring to the tach sensor. It could be that the TCM is losing power and frequently resetting. That could happen from a bad EEC relay.
When I unplug the tach sensor, the tranny still hunts.
As for the EEC relay, when just sitting still, it tests good. Could it cut in and out while I am driving down the road? That is definitely a new take that I had not thought of.
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Logistics Pro
Joined: Feb 2011
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From: Townsend, MT
New (known good used) EEC relay didn't change anything.
I have done a bunch more fiddling. I have found:
Unplugging the tach sensor doesn't stop the hunting.
Unplugging the TPS dosen't stop the hunting.
Unplugging both the TPS and tach sensor doesn't stop the hunting.
At WOT, the tranny shifts great and doesn't hunt.
The only way to stop the hunting is to unplug the ECM.
What do the solenoids in the valve body do?
Frmr Ford Trans Engr
Joined: Aug 1999
Posts: 24,730
Likes: 2,658
From: SE Florida
I know that, you've said that. I think the problem is in the wiring not the sensor. But if you want to chase other things, that's fine with me.
You keep fiddling, and asking for help, but you don't check what's offered. I don't think you want to fix this.
They take the commands from the TCM and change the valves in the valve body to make the trans shift. Now I suspect you'll want to change the solenoids. They are not the problem.
You've done enough testing to pretty much determine the problem is in the wiring between the tach sensor and the TCM.
You keep fiddling, and asking for help, but you don't check what's offered. I don't think you want to fix this.
They take the commands from the TCM and change the valves in the valve body to make the trans shift. Now I suspect you'll want to change the solenoids. They are not the problem.
You've done enough testing to pretty much determine the problem is in the wiring between the tach sensor and the TCM.
Fleet Mechanic
Joined: Aug 2011
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It's not the wires between the tach and TCM, you can short out those wires all day long and the tcm will just go into tach less mode and shift late. Your problem sounds exactly like the tcm is loosing ground and reseting, the tcm controls the ground side of the shift solenoids and the eec relay supplies the power side, the ground is on the rad support but you can also run a wire from battery negative to I believe pin 60 or 59 which should be a thicker black wire with a white stripe or just black, check/try that and let us know what comes of it.
Frmr Ford Trans Engr
Joined: Aug 1999
Posts: 24,730
Likes: 2,658
From: SE Florida
If it is an intermittent short to ground it will cause erratic shifting. A solid short will produce late shifts.
