Hi all,

I have had a strange problem with my 1993 4X Dakota (3.9 Liter MPFI):

The truck runs fine mostly but sometimes it will develop a steady, pronounced miss almost like a burnt exhaust valve only it's intermittent. Sometimes if I lug it it will start other times it just happens for no apparent reason.

I did a fuel pressure test with the vacuum line to the pressure regulator unplugged as specified in my Haynes manual and the pump seems to be running about 2-3 PSI above the spec in the book. (around 41 PSI is where it runs at)

My fuel gauge also has quit functioning properly; it will read full when I first fill then later it will read half but other than that it just sits on 'E' all of the time.

I am thinking it may be the pump is bad but that is a pretty expensive guess so any opinions would be appreciated. I like to fix her myself but I may have to eventually take it to a mechanic.

I ran a compression test with not the greatest results but if that were the culprit here wouldn't it be consistent instead of intermittent ?

 

Have you checked your plug wires, plugs, Cap, rotor?

 

Yes a tune up could help. Do you have any codes come up?

The guage is usually a corroded tab on the fuel sending unit.

 

Try running fuel injector cleaner through it. Thats a cheap, easy place to start. Otherwise check the ignition system like mentioned above. Also check the power splice to the ASD and fuel pump relays for corrosion.

As for the gauge problem, its probably not the pump. This is from faq2...

 

I had a miss in my jeep and drove me nuts cause it was doing exactly what you're saying. One night I stopped on the side of the road to take a leak. And pop the hood. Opened it up and noticed a lightning storm under the hood. Next day, bought wires and plugs. Fixed it.

 

Clean the system...run a can or two of Seafoam in the gas tank.

 

I agree with tmacdakota. I used that stuff when i first got my Dak and it fixxed just about everything and blew it out the tail pipe, Literally!

 

thanks for all of the replies guys!
I will examine the ignition parts but I did replace them not too long ago. I have run injection cleaner through the system but I will try the Seafoam thing and see how that does.

Will report back when I have tried the suggestions given here.

 

i know when my truck needed a tune up it would occasionally miss fire. the proble gradually went from occasion miss fire to "what the ****". turned out it was the cap, rotor, and ignition coil... my first suggestion would be to check the cap and rotor to see if it looks burnt or is black on the end and the plugs...if they are replace them or clean them off and they last a bit longer...