[benjy]

Okay I have done the following plugs wires cap rotor air filter pcv valve fuel filter all have been replaced! This truck gets 17-18 mpg average and 20 or 21 on long runs that im happy with! It runs decent starts every time but is just a tad weak in acceleration and wants to do this stupid cut out under full throttle its real bad you have to take your foot out of it its like a wa wa wa wa bucking any ideas on where to attack this problem? Its an 89 3.9 with the auto od in a 2wd dakota

 

[93DakspoRT]

well its carbed so its not a power monster. try checking out your egr valve.

 

[benjy]

No its tbi and the egr is unhooked and vac lines are plugged i know they werent monsters but this thing runs nothing like the 89 ram i had with the same engine

 

[madmopar]

a holley sticker on the back window adds 30hp. just kidding. did you check all vacuum lines?

 

[DRAGN94]

if its tbi then check your map sensor (front of TB) or u have a vacuum leak

 

[benjy]

well then my dual Jegs stickers should be worth 14-18 hp then lol yes ive crawled all over this truck it just puzzles me what it could be

 

[98R/T]

check your cat, or o2 sensors?
just a thought

 

[DRAGN94]

check your cat, or o2 sensors?
just a thought

the o2 on a OBD1 vehicle is pretty useless, just maintains base injector timing. and the cat with or without on the early gens didnt do a dam thing

 

[98R/T]

scratch that then lol

 

[benjy]

no cat glasspack single exhaust and the map sensor is new as well with the tune up

 

[jacob]

run a fuel pressure test could be fuel pump

 

[benjy]

run a fuel pressure test could be fuel pump

Thank you that was one of my thoughts it seems to be a lack of fuel and I would rather it be the fuel pump that those tbi injectors they are way to $$$$$$$$$$$$$$

 

[DwnDak]

I had what seemed to be the same issue a few summers ago.... it was a vaacuum issue... but yours doesn't sound as bad as mine...

how the hell are you gettin 20mpg outta ur 3.9!!! hahaha

 

[benjy]

I had what seemed to be the same issue a few summers ago.... it was a vaacuum issue... but yours doesn't sound as bad as mine...

how the hell are you gettin 20mpg outta ur 3.9!!! hahaha

the 20 is highway long trips and i usually drive with a light foot

 

[jacob]

i get like 22

 

[slade]

mine got 23 at 65 thats no lie but does it start hard like its not getting fuel? furl pumps are actually a common problem with daks

 

[benjy]

mine got 23 at 65 thats no lie but does it start hard like its not getting fuel? furl pumps are actually a common problem with daks

Not at all it fires every time but I do know that if the pump is weak it may start okay

 

[tripovermyego]

Not at all it fires every time but I do know that if the pump is weak it may start okay

Almost sounds like a vac issue to me. When my fuel pump started going out, it would take like 10 secs of turning over to fire up. And the fuel gauge didnt work until it got to 2/3 tank then would go to empty again. I replaced the fuel pump, and now it turns over like twice and is purring like a kitten. Fuel gauge doesnt work at all and the fuel light is on now. But Ill be taking a closer look at it to see what that is.