I have a totally bizarre problem that I just cannot figure out. 94 Jimmy w code. I think it's electrical but I'm not sure. Basically, every once in a while when you start the truck and go to drive it, it seems like the transmission is having problems. When you start off in 1st, it doesn't want to move out of its own way, and seems to just rev too high for how fast its moving. Basically, it feels like either the 4x4 is on or the parking brake but this is clearly not the issue. Almost like it is in limp mode. It just sounds totally wrong and will not go into 4th gear once you get going. The transmission fluid in full and clean.
I noticed yesterday that when I primed the fuel pump before starting the truck, it did not sound right. It is usually the normal humming noise but what I heard was just not normal. Sure enough, the transmission acted up right after that, and every time it does act up, I notice that the fuel pump does not sound right.
All you have to do to make it go away is turn the truck off and back on again. The fuel pump is a year old, and it is a delphi. My last fuel pump only lasted 3 months and when I switched it out it became clear that the wiring on the sending unit was melted. I was hoping that this was simply a defective pump, however now I'm leaning more towards a wiring problem.
I had an issue a while back where my ign/gau fuse had melted, causing the transmission issues because that fuse runs the vss and had sent the transmission into limp mode. I inspected this fuse a couple days ago and it looked fine. Does this fuse run anything fuel pump related? I am very unfamiliar with electrical systems and don't even know where to begin. Perhaps an issue farther down the wiring of this fuse? Any insight would be very appreciated.

-Melissa

 

that fuse runs all sorts of bs. stupid stuff too, stuff from like the transmission all the way to the rear defrosters. theres a whole test procedure you are supposed to go through and eliminate each thing one by one. so like unplug your rear defrost, your a/c or whatever else. i forgot off hand what the procedure is, i googled it a while back and found it somewhere

i had a similar issue about a year back and even now my ign/gau fuse still blows after about 4 hours of driving, my truck is just a offroad truck so my way of fixing it was just to carry extra fuses.

i believe mine was a computer issue but was also told it can be a ignition switch issue too. i found out my computer wasnt grounding the proper solenoids inside the transmissions when it was supposed to, so all i did was find out what the computer was supposed to send to what wire and bypass it so it only runs in 1st gear which is all i need

but yeah see if you can google around the ign/gau fuse issue to see if you can find anything. also when my fuse blows my gauges quit working so i knew when to replace that fuse. replace that fuse anyways just to make sure its not bad, and check the connections inside the fuse box make sure they arent all melted too

 

heres all those procedures i was talking about. its not exactly your problem but it might help

 

That fuse also runs the Alternator Charging System and Oxygen sensors. A few possibilities are:

1) O2 sensors are off, so its running rough at idle due to the unknown AFR

2) Since the charging circuit was down, your voltage may have dropped. This drop in voltage could lead to a drop in fuel pressure (among other things like ignition issues). This could lead to some problems as well.

On my last off-roading trip this fuse blew while I was doing a long hill climb. By the time I made it 2/3s of the way up the car would barely run. At full throttle it sounded like I was out of gas, and just couldn't move the car over the rocks. Replaced the fuse, and everything went away (until the fuse blew again of course)

 

I just had to put a new shift solenoid A in my 94 jimmy 4x4 with 4l60e. It had no 1st or 4th gear that i mistook as sluggish or slipping. But when i paid attention my truck shifted under mild throttle at 40-45 mph for it's FIRST shift. That's not right, it was taking off in second. When that solenoid goes out the truck only has 2nd and 3rd gear. the truck should shift out of 1st at about 20-25 mph