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Discussion Starter · #1 ·
My truck has 280K miles on it. Transmission shifter is quite sloppy, recently had to start putting in neutral more often than not to get it to start. Just yesterday, I noticed for the first time the RPM was varying up and down intermittently about 300-400 rpm. This happened at lower speeds as well as higher speeds. I pulled it into the garage and have it sitting for now.

I've read some items on the tach sensor, but these seem to be more related to erratic, hard shifting. My truck doesn't seem to be shifting, so I wonder if this is something with the torque converter. Any suggestions?
 

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What transmission is in the truck? A three speed C6 or a four speed E4OD?
 

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Are you hearing the engine change, or is the tach just bouncing? If the engine is changing, you might want to look into fuel supply issues. If the tach is bouncing, it most likely is a short in the wiring. The tach sensor is right in front of the IP, with two wires running from it. If they're bare anywhere, they will short out or touch each other and cause tach failure, or erratic readings. Usually just cover the bare spots and you're back in business. An erratic tach will cause the transmission to shift funny, but having to put it in neutral to start it sounds like a neutral safety switch problem. Mark knows a whole lot more than I do, so I'll ask him to correct me if anything is wrong here
 

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The first thing to do to diagnose an E4OD problem is to check for codes. Here is how to do it: www.troublecodes.net/ford
 

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Discussion Starter · #6 ·
Are you hearing the engine change, or is the tach just bouncing? If the engine is changing, you might want to look into fuel supply issues. If the tach is bouncing, it most likely is a short in the wiring. The tach sensor is right in front of the IP, with two wires running from it. If they're bare anywhere, they will short out or touch each other and cause tach failure, or erratic readings. Usually just cover the bare spots and you're back in business. An erratic tach will cause the transmission to shift funny, but having to put it in neutral to start it sounds like a neutral safety switch problem. Mark knows a whole lot more than I do, so I'll ask him to correct me if anything is wrong here
The engine is actually changing rpm.
Are you hearing the engine change, or is the tach just bouncing? If the engine is changing, you might want to look into fuel supply issues. If the tach is bouncing, it most likely is a short in the wiring. The tach sensor is right in front of the IP, with two wires running from it. If they're bare anywhere, they will short out or touch each other and cause tach failure, or erratic readings. Usually just cover the bare spots and you're back in business. An erratic tach will cause the transmission to shift funny, but having to put it in neutral to start it sounds like a neutral safety switch problem. Mark knows a whole lot more than I do, so I'll ask him to correct me if anything is wrong here
I am hearing the engine change, but it’s not a loss of power like you feel with fuel issue. Engine surges about 300 rpm and then backs off. Does this every 5-10 seconds. Never happened before but once it started on my last drive, it continued the whole way home.
 

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I have had the engine surge with no noticeable loss of power, and had a plugged fuel filter, and the indicator light in the dash hadn't activated yet either.
 

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Discussion Starter · #9 ·
Fuel filter changed, no luck (but it was due so no issue) So I checked codes with an OBDI reader. Only code I get consistently is 67. Checking book, this is either a/c clutch or neutral safety switch. I was having problems with a very sloppy shift lever, would not start in park. I checked the steering column and found loose bolts. Tightened this all up and reset the shift select indicator. Still getting code 67. I am still getting the engine surging. I am pretty sure this is the torque converter cycling.

In the process of troubleshooting. I blew fuse 8. I replaced it and it was fine for a bit. Now it blows every time as soon as I put a fuse in, ignition on or off. Looking at fuse 8, it is a huge circuit. I really can't drive with this as no speedometer and I get the very hard shifts. Any suggestions on tracking this short down?
 
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