Hey gang, got a little problem with my beater 87 3.9L carbureted 4x4 dakota, 132k on it. At highway speed, especially going uphill, it bogs and surges. Not like the trans is slipping, but like it's starving for fuel or the ignition is dying out. If I let off the gas a bit and go slower it goes away. If it happened under load at any speed, I would suspect ignition breakdown or fuel starvation, but I can't get the symptoms to occur in any other situation than at highway speed under mild load. Plugs look good, nice and tan. Doesn't use oil, smells like it runs a bit rich at idle, but the mileage has always been good so I've never messed with the carb. The speedometer stopped working around the time I first noticed this problem. I verified that it isn't the speedo itself, rather it looks like the problem is at the transmission end of the cable. I see there's a VSS inline with the speedo cable near the firewall. Could this cause this type of problem? What does that VSS do on a carbureted vehicle? I really should get a shop manual and figure it out, but I figured someone here may have some insight? Thanks!

 

It may be something like the EGR valve or a vacuum leak.

 

thanks, I'll look into them. It doesn't appear to have any symptoms of a vacuum leak at idle or? Anyone else have any ideas? Thanks!

 

94 Dakota, 5.2 176k on in stock engine and tranny t-case, all that... i have changed the plugs and wires in the past three months, and i JUST got done putting a new coil pack on it... and the symptoms still emerge... I can drive it all day, and then somewhere somehow, it will start to seem like it is starving for gas, and i know that there is gas in it and al that, but yet, for some reason, I think there has to be something in the fuel... i have put a whole bottle for a 22 gallon tank of Carb and injector cleaner in it in the past 2 weeks, and it always seems to fix it for a few days...
I just cant get it to run fine normally under all conditions...
have had the truck for two years and a few months now and have never had this problem until recently...
bought it in Kansas, Cold winters harsh hot summers...
moved to tennessee just after i bought the truck and just last summer it started doing this, and that is when i put the new plugs, rotor, distributor cap, and what not on... could this truck be up a ****s creek?
anyone?
please help!

 

Mine had the same problem as the OP. Very intermittent. Sometimes would do it for several miles, off and on, and other days wouldn't do it at all. Finally came to the conclusion that it was worse on wet days, and began to suspect plug wires. Did the tune up swap (plugs, wires, cap, button, oil change, filter change) problem hasn't been back since. Thinking the shielding on one or more of my plug wires was giving out. The previous owner seemed to be under the impression that as long as he kept the outside clean (which he did) the rest would take care of itself.

Not sure if this is your problem. With mine, speed or load didn't really seem to be an issue. Seemed all I had to do was let off the gas, and it would settle itself out.