Well back again. Right before I went overseas my alternator failed on me. So I left my truck tucked away for 3 months. Came back replaced the alternator, and got a new battery, (changed oil as well). Anyway drove around 500 miles after that and then it happened again, my speedometer started to drop down erratically and I could feel the truck lose a little umph. Anyway, that only happened once. Drove it the next night - felt a little sluggish and thought I was definetly going to be stuck in the rain but I made it home, parked and then we just going to move it to the garage when it wouldn't start, just tick tick tick tick. Let it sit for the night and started it up in the morning and all good. Sounds a little rough under the hood. Just dont know where to begin. Checked the voltage getting 12.25 not running and 13.9 running. Anyway gentlemen - let me know if you have any input.
It's a 98, 140k miles. Let me know if you need any other info.
thanks in advance

 

Its not a alternator problem.

Sounds kinda like your VSS (vehicle speed sensor)is going bad, but we need more info.

When does it happen? Driving up hill? When giving it gas? Taking off from a dead stop?
Is the check engine light on? When was the last tune up done to the truck?
What grade of gas are you using and did you treat it before you parked it for 3 months? Was the gas tank full when you parked it?
Where do you live?

 

2x on the vss...my truck acted the EXACT same way ...new vss cured it

 

Alright let me answers these ?'s - The problem happens when giving it gas (the speedo dropping etc), I dont believe it happens on a hill. Check engine light is on, will read the codes when I get back to the truck. I did a tune up (myself) just before I left. (A tuneup to the best of my knowledge), I'm using silver gas. It was around a half a tank for 3 months.
I'm living in west virginia for a while (tell sept), but reside in northern nj. And always travelling between there and philly.
Let me know what else you need to know. Thank you. I'm looking into the vss today.

 

If the Speedo drops, it is the VSS, if the tach drops, it is the alt. You are looking at a new VSS. Don't mess with the old one until you have a new one in hand, odds are that it will fall apart when you take it off.

Use premium fuel ALL of the time, and if you are leaving it for a while, always fill it up. Less room for air to condensate inside the tank. I would add a can of seafoam to the tank before you leave it as well, but that is just me. Every winter, I fill the tank in my boat and add a can of seafoam.

Order a new VSS and get the codes read.

 

Ok finally checked the codes got a p1316, p1448, p0305, p0300. Looked into replacing the VSS doesn't seem that hard of a job or too costly, so will see if its damaged tomorrow. Should I just go ahead and replace plugs and wires, I did it about 30k miles ago. And saw maybe it could be a sticky valve? Would love to tackle that job - but would need a little step by step action. Anyway let me know, I'll be stranded where I'm at for a while and will be able to take lots of time out for the disco.

 

Replace the VSS, then do a tune up.
Dont worry about sticky valves right now.

What type of oil are you using and how often are you changing it?
Using cheap oil and going to long between oil changes can cause a sticky valve or two.

 

Just an update of what happened. I've been real busy, anyway. The vss came in yesterday and I put it in today and what a difference. I reset the check engine light, so we'll see if that was the cause of it. The truck now doesn't crunch really hard when going from say P to D, or D to R. Before it would hit really hard in those times. It isn't struggling as much going up hill and staying with a steady acceleration, not feeling like its getting no gas or missing a gear. I haven't driven over 35 yet so we'll see what happens when it does. Thanks for pointing me in the right direction. I also followed a step by step on discoweb.org in their tech section.
The vss I took out was covered in gunk, and the "spindle" in the middle was easily pulled out of it's slot.
thanks.

 

Thank you for reporting back.

 

Glad you were able to resolve it. Was it it a simple replacement?