7.3 idi tac issue

[mrmatthewhenning]

I have a 93 7.3 in a 250 with the e4od. I have changed the tac sensor. I have tested the wires. The tac works when it wants. I can't find the relay everybody talks about on the drivers side fender. The tac either works perfect or not at all. Everything else electrical in the truck works perfect. Its a gamble when it starts if the tac will work. I turn the truck off at every stop sign and restart. Eventually it gets going and runs fine as long as the truck is hot. When it cools down in the Florida sun the problem starts again. Some times its on the third start. 1/4 mile from home. Other times its 10 trys by the time I get to work 30 minutes later and still no tac. Mind of its own. Any thoughts? I know this is a beatin topic but I'm at a loss. I own 3 idi's right now and have own others in the past. Have always ben able to over come this problem just not on this one.

 

[IH-GM IDI]

Sounds like an air gap issue, if it looks like the timing cover has been off might be worth making sure whoever's did it prior assembled it properly

 

[BeastMaster]

According to my wiring diagram, both the tach dash gauge and the E4OD need the tach signal.

I have an E4OD that had tach sensor problems. The TCS would constantly misbehave.

Do you notice both gauge and transmission problems? Or just the gauge?

 

[mrmatthewhenning]

Trans goes into limp mode. I just shift it manual and it runs ok.

What do you mean by a air gap?

 

[Shadetreemechanic]

I think he is referring to the gap between the tac sensor and the pump gear, though I am not sure what would change that other than maybe a thick gasket on the timing cover.
I had this problem on a truck about 10 years ago. After changing sensors several times I changed the instrument cluster and the problem disappeared. If you have another laying around it might be worth swapping for troubleshooting purposes.

 

[IDIBRONCO]

other than maybe a thick gasket on the timing cover.

There shouldn't be a gasket under that housing at all. Maybe somebody decided that there should be one and made their own.

 

[quickster]

The tach on my '91 f350 w/E4OD never works till it warms up. Once the cab gets warm, the tach will work. Truck runs fine, just getting old. Mine never goes into limp mode though. If you rev it up a bit, it will jump up, but then back to zero. There's a joke in there some where if someone wants to put it together. HA!

 

[IH-GM IDI]

Yes I am referring to the space between the sensor and the pickups on the gear. They can be pretty sensitive to how close they need to be to work properly. So much so that even getting an extra quarter turn on them can help this problem, or even the difference between a hot and cold motor can change how it'll behave if it's right on ther edge of tolerance.
And as others have said it could also be in the cluster, but I wouldn't think the cluster could make the tranny go limp I've driven with my cluster unplugged and had no shifting issues

 

[Shadetreemechanic]

Cluster will make the transmission go into limp mode. That was the issue I was working on when I replaced my cluster. I had just rebuilt my E4OD and it kept throwing tach sensor code and going into limp mode. The guy who built the transmission replaced the cluster to get it to work. The tach was a symptom and he had seen bad clusters before.

 

[Slicknik]

Vss sensor could be failing as well

 

[rsaltaresjr]

My e4od intermittently goes into limp mode for no apparent reason. I used to have to pull over, shut the truck down and restart to get it shifting back to normal. Then I noticed it would go into limp mode when I toggled between the odometer and trip meter. If I kept pressing the button repeatedly eventually the limp mode would go away. So now I can go months without any issue, but when it reoccurs I just press the odometer trip button a few times as I drive until it goes back to normal. Not exactly sure what the correlation is between the odometer trip and the trans limp mode. In my case there’s definitely something wacky going on with the cluster though.