So I just got a 98 Dodge Dakota with the 3.9 a week ago and I am having an issue with it. About 1 out of every 10 times I drive it, it will have a rough idle from the start and stay that way, running very sluggish, until about 15 mph. Once I hit 15 mph it's off to the races and running great again. I have no clue what is causing this. It has a new TPS along with a throttle body spacer. However, the catalytic converter has been removed and it is straight piped, but I would imagine that if that was the problem that it wouldn't be intermittent like it is.

Any help would be great. I've searched these forums and searched google for hours now and can't find anything.

Thanks!

 

throttle body spacers do nothing for fuel injected autos

You need to clean the throttle body

 

Yeah, I didn't put the spacer on it, the previous owner did. I will get the throttle body cleaned and let you know what happens. Thanks.

 

Clean the Idle Air Control valve (IAC) while you are at it. Best way to clean the IAC and TB too is to remove it from the intake, then remove the IAC, Throttle Position Sensor (TPS) and Manifold Absolute Pressure (MAP) sensors from the TB. Then you can use a shop rag soaked in TB cleaner to gently clean the black crusty crud off the pintle end. Put a drop or two of 3 in 1 oil on the shaft to lubricate it. Do not move the shaft in and out, it will damage the stepper motor.

Then clean the TB with a rag and TB cleaner. be sure to clean the IAC orifice on the TB and lubricate the IAC's o-ring with clean motor oil. Spray the springs and linkages on the TB with spray silicone and use a new gasket when you reinstall the TB.

Jimmy

 

I was looking online because I've never done anything with a throttle body and I saw something about removing the throttle body can throw the computer off. Do I need to worry about that?

 

No it won't cause any problems with the PCM, other than you may notice a change or improvement in the idle after you drive the truck a few miles. That is not because anything is wrong, it's just the PCM adjusting to the now-cleaned IAC. Just be sure the ignition is off before you disconnect and then re-connect the sensors.

JImmy