ricker2
08-01-2004, 01:22 PM
I have a '98 Dakota with a 3.9L Magnum engine with 54,000 miles that I purchased used. Ever since I bought it I noticed that at certain speeds above 40 mph when slowly accelerating and especially up hills, it feels like it labors and makes the truck shake. At idle it's smooth with no misses or out of the ordinary noises.
The RPM's remain constant while this happens and there are no sounds heard that would indicate any misfires. It feels like a deadspot, as if the fuel is either too rich or lean. Now this only happens between 45 and 60 mph. At 60 mph and beyond it runs smooth. But between 45 and 55 when trying to maintain those speeds something is causing it to run really rough until I accelerate out of that speed or drop below it. Yep, I thought it was the TPS, too. wink.gif
Hard Acceleration is excellent and goes thru those speeds without any effort but if I'm at 50 and accelerate gently I have to give it more gas to get thru the rough spots. Because it has good strong acceleration I feel that rules out the fuel filter.
Here's what I've done so far:
Changed Plugs, wires, PCV, distributor cap and rotor. I put in 2 new Oxygen sensors and a new TPS (Throttle position Sensor). I ran at least 5 tankfuls of gas with different brands of Fuel injection cleaners including Lucas and Techron brands and even sprayed injector cleaner directly into ports with engine running.
I took it to the Dodge Dealer and had the Computer ROM flashed since it wasn't done since 2000. They ran computer diagnostics and didn't find any codes before or after they ran the tests. The battery was disconnected and I thought I could drive it and "retrain" the computer but maybe I did it wrong.
I read somewhere that unbalanced tires could cause the problem at certain speeds to I had each tire balanced and rotated. Shocks (stock OEM) were inspected and no fluids were leaking so I'm assuming they are ok. The balancing did make a difference in the shaking at higher speeds but it's still happening between 45 and 55 mph. By the way, the jerking/shaking feeling is not felt in the steering wheel but you can feel it as you sit behind the wheel...like a frontwards/Backwards jerking as if you're trying to drive thru sand when you accelerate.
My only guesses now are to get the transmission checked or have a garage completely clean the injectors. Maybe the fuel filter should be changed along with the fuel pump. I've even thought the alignment could be checked due to excessive toe-in, I don't know. It really feels more like it's transmission related because of the way it acts. Could a PCM malfunction cause this without showing any error codes?
This is really getting very expensive. I'm hoping one of my friends here has experienced the same problem. Any ideas will be greatly appreciated!!
The RPM's remain constant while this happens and there are no sounds heard that would indicate any misfires. It feels like a deadspot, as if the fuel is either too rich or lean. Now this only happens between 45 and 60 mph. At 60 mph and beyond it runs smooth. But between 45 and 55 when trying to maintain those speeds something is causing it to run really rough until I accelerate out of that speed or drop below it. Yep, I thought it was the TPS, too. wink.gif
Hard Acceleration is excellent and goes thru those speeds without any effort but if I'm at 50 and accelerate gently I have to give it more gas to get thru the rough spots. Because it has good strong acceleration I feel that rules out the fuel filter.
Here's what I've done so far:
Changed Plugs, wires, PCV, distributor cap and rotor. I put in 2 new Oxygen sensors and a new TPS (Throttle position Sensor). I ran at least 5 tankfuls of gas with different brands of Fuel injection cleaners including Lucas and Techron brands and even sprayed injector cleaner directly into ports with engine running.
I took it to the Dodge Dealer and had the Computer ROM flashed since it wasn't done since 2000. They ran computer diagnostics and didn't find any codes before or after they ran the tests. The battery was disconnected and I thought I could drive it and "retrain" the computer but maybe I did it wrong.
I read somewhere that unbalanced tires could cause the problem at certain speeds to I had each tire balanced and rotated. Shocks (stock OEM) were inspected and no fluids were leaking so I'm assuming they are ok. The balancing did make a difference in the shaking at higher speeds but it's still happening between 45 and 55 mph. By the way, the jerking/shaking feeling is not felt in the steering wheel but you can feel it as you sit behind the wheel...like a frontwards/Backwards jerking as if you're trying to drive thru sand when you accelerate.
My only guesses now are to get the transmission checked or have a garage completely clean the injectors. Maybe the fuel filter should be changed along with the fuel pump. I've even thought the alignment could be checked due to excessive toe-in, I don't know. It really feels more like it's transmission related because of the way it acts. Could a PCM malfunction cause this without showing any error codes?
This is really getting very expensive. I'm hoping one of my friends here has experienced the same problem. Any ideas will be greatly appreciated!!