Hi guys,
I'm the happy owner of a standard 4x4 1989 Dakota Sport 3.9L (TBI). Since several weeks, I have a hesitation problem at low throttle, almost like it is misfiring. It happens:
- when driving, at the moment where the speed is stabilized, whatever the speed is.
- in neutral, when I slightly press the gas pedal. It is not an intermittent problem, it does it all the time.

I already did a tune-up:
- Plugs, wires, distributor cap and rotor, ign coil, hall effect sensor.
- I replaced the Throttle position sensor.
- I cleaned the EGR valve (was completely clogged).
- The fuel filter has one year.

The idle and acceleration are the same as before, I only get the problem at very low throttle. It does not stall, but when the engine is fully hot, it is hard to start again, I have to wait like half an hour.

I don't get any codes.

I love my truck, but now I'm fed-up.
Any advise???

 

if you have access to a vacuum gauge, measure the vacuum of the engine at idle; should be around 17-21 inHg. As you crack the throttle, it should drop down momentarily and then jump up to around 25 inHg. If it drops the more you open the throttle, you have a clogged exhaust, which it sounds like you have.

 

thanks mate. I'll look at it as soon as I can. I wonder if the IAC could be ivolved too?

 

well, if it can help someone with a similar problem:

I ended loosing the distributor retaining bolt and rotate it to get a better timing...problem solved. In neutral, I can still hear some kind of "weak rattle" but it doesn't hesitate anymore. I even got a lot better acceleration.

The only thing is that the idle speed is now around 1000-1100 rpm. I don't know if I can adjust it, maybe the screw on the idle solenoid...anyway I'll bring it to the garage to have it timed properly.