I have a 1988 Dakota v6. Drove it to work ran fine on the way home I could hardly get to 50 miles an hour. At stop signs it wanted to die. I have changed the spark plugs and wires and distribuator cap the map sensor throttle positioning sensor 02 sensor even cut out the catalytic converter thought maybe that was plugged. It starts up fine but idles rough and a little black soot comes out of exhaust. Does anyone have any suggestions? Thanks

 

Not a mechanic here, have you checked fuel pressure and or filter etc?
I have a 1993 V6 that is FI .... and wants 45-50 psi at idle .... I do not know if 1988 is carburetor or FI. .... Just sounds like you covered the basics for sensors .... time to look at fuel.
Also would help if you do the key dance and see what codes are listed.

 

I put a new fuel pump on it when I got it. I’ll check fuel pressure hopefully this week. Not for sure what the pressure should be. I’ll have to do some research. Thanks.

 

FWIW, I installed a new fuel pump and got 5k miles on it .... chasing a problem I pulled it back out and the case of the pump was split and the guts were falling out of it .... still pumped fuel but not for long.
And I bought the most expensive one RA had, thinking it would last awhile. .... You never know.
Have you replaced the filter lately?
I have a 1993 Dodge Caravan with a 3.3 V6. It has a fuel pressure regulator on the fuel rail ... seems most vehicles the pressure regulator is built into the pump. Dunno about yours.

 

88 Should be TBI, so, fuel pressure should be like 15 psi. There is no shcraeder valve to check it though, gonna need an adapter.

 

Fuel pressure test was 15 pounds. I unhooked the lines on the egr valve there was no change at all. Should there have been?

 

Not really. If the valve is stuck open though, that'll cause some issues. If you have a vacuum pump of any description, you can test the valve.

Do you have a scanner that can read live data? See what long and short term fuel trims are doing, and have a look at the other sensors as well, see if what they are telling the PCM seems reasonable.

 

Except for the onset this sounds like my 94 v6 Magnum ran when I bought it. I ended up doing the plenum, had the intake tanked, new WP, Timing chain, and all new sensors. The intake was heavily coated with baked on oil. That, oil in the intake, is what I would look at since the symptom list sounds the same. IDK if the early models had that problem or if they have the same style intake.