Newbie here. I have a new to me, 1994 Dakota, 2WD, LongBed. Transmission rebuilt about 20k miles ago. Truck only had 110k original miles, Was garage kept all its life.
I have put in new plugs and a new starter.

Today, I flushed heatercore and drained cooling system, and replaced T-stat.

After doing this, I noticed the truck was running a tad rough. I took it out on the road, and it stalled on me.
I could then start it fine, and it seem to idle fine-- but when I put it into R, D, 1 or 2-- it lurches it will begin to go back or forward and then stall.
Somehow I was able to get it going again, and got it home-- but still has same issue, and I can't get it to go forward or backward.

I notice that the speed sensor at the back of the transmission is all wet, and when I unplugged it, had transmission fluid in it.
I cleaned this all up, and reinstalled, but this did not help.

I tried to pull codes by turning the key, and seem to get either 1255 or 355.

This is a nice rig, and I really doubt the transmision is gone--- I have been driving it all around town before this.

I do not see that I disturbed anything when I changed the T-stat.

Sure would appreciate any ideas!!!

Thanks guys--

Don

 

Post what motor it is.
On my 94 3.9L there are two sensors that are mounted right next to the thermostat housing. One of them is Engine Coolant Temp sensor the other is for the dash. It sounds like you may have got one or both of them disconnected. Or they may have gone bad. Its 27 years old. the Engine Coolant Sensor tells the computer how warm the motor is and when you hit the pedal how much gas it gives the motor.

EDIT- Oh yea the codes. Try to get used to the spaces between flashes. 12 indicates you have had the battery disconnected in the last 50 starts. 55 indicates no more codes. There is a link to code list in the FAQ section. That page is very good to read all the way through so you get some idea what you are in for. Sounds like you got a good deal.

 

Thanks-- Yes it is the 3.9. There is a really small electrical connection right near the heater core hose, that comes in near the thermostat housing-- I was very careful not to damage it, but it looks very delicate.

I am wondering about my IAC Valve????

 

Try reading the codes again.

Look for vacuum lines in the area too.

 

Take a look on the other side of that heater hose. There should be another sensor. The single wire one is the sending unit that tells the dash gauge what to say. I haven't found it in my FSM yet but the ECT that tells the computer I think has two wires and since it shows the single wire sensor on the outside of the heater hose the other one should be inboard of it.They changed this after 94 to a one sensor setup. They are pretty cheap, I paid less than $20 for both 7 years ago at Carquest. I think they are Advanced Auto now. It's a PIA but if you go slow and set yourself in a stable position before sticking the socket extension down there you can remove and replace without taking a lot of stuff apart.
You can clean the IAC with carb cleaner. Try not to spin it when you have it out.

 

BLUF--- It is now clear that I have a rough idle condition, and rpms do not stay steady when holding down gas in idle. Engine will run and idle, but it is rough. When I put in gear, it immediately stalls.
----------------
I removed, cleaned and reinstalled the IAC. I found a cracked vac line (down near canister in front passenger side) and repaired it. I removed negative battery cable and reinstalled.

None of this helped. Still get same trouble codes-- either 1255 or 355.

Any more ideas of what I can try. I do not see any other vac lines or wiring that looks out of place....

Thanks!!!!

 

I'll be repeating some of what 94dak already said. The 12 code simply means you've disconnected the battery within the last 50 cycles. The 55 code means it's done reading codes. So for your purpose, ignore the 12 and 55 codes. I have no idea what a 355 code is. As far as I know, it doesn't exist so I do not know how you are reading it. If I drop the 55 at the end, it's a 3 code. A 3 code does not exist either. So you either invented a new way of reading the code or you have a goofy code reader. Go back and read it again. I attached a video on how to precisely do that. Get back to us with your findings. If you have a code we can tell you what it corresponds to and could make your life easier tracking down your problem. Based on what you're saying, a code does exist so you might be in luck.

 

Thanks. I only have the 12 and the 55-- nothing in between. At first I thought the 1 and then 2--- was really 3 flashes-- but it is actually a 1 pause, and then a 2.

If I let the truck idle for a while, do you think it may give it time to throw another code? I have disconnected the battery today, when I cleaned the IAC valve.

Should I maybe just go and replace that engine cooling temp sensor? That is the only think I was working near, when I replaced the thermostat.

Thanks so much for your help!

 

Yes, a code will clear if you disconnect the battery for awhile. Try running the truck a bit and see if it throws a code.

If you have a bad sensor the OBD1 should throw a code. Otherwise, a new coolant sensor is probably a $15-20 gamble and if it doesn’t fix your problem at least you wont have to worry about your coolant sensor for awhile and you can scratch it from your list. Your wallet, your call.

 

Yes. Let us know if it works. Read the FAQ page it might help.