98 OBW hesitation @ low rpm

[rezmutt]

I have a slight, though noticable, hesitation when I give my 98 2.5 auto OBW some gas. It happens when it's cold and hot, though not consistently. The same happens when accelerating from a stop.

 

I've got new plugs, but not wires (yet). Could it be that easy? The car has 102,000 miles on it and otherwise runs well.

 

Unrelated: When I bought the car in June, it had severe torque grab. I changed the front and rear differential oil, and also changed the trans fluid. Now, absolutely no grab. It's like a new car.

[Commuter]

I have a 97 OB and went thru this same issue neary 3 years ago. (I had just over 100k miles at the time.) The problem? Carbon build up. Yeah I know... weird in this day of computerized control, but that's what it was. CCR has noted in the past that these engines are bad for carbon. My dealer did a MotorVac and it cleared it up, for a while. When I would detect it coming back, I would run a tank or 2 of premium, and/or some cleaner, and usually all would be good for a while again. Earlier this year, the problem was getting worse and the premium gas etc was not solving the problem. I changed out the O2 sensor and things started to improve noticably. It's taken a while, and some premium / cleaner, but it seems to be about 95% gone right now. I don't think I will have to do the MotorVac again.

 

My symptoms were a hesitation/stumble when starting off. Not all the time, not consistent. Between 600 and 1000 rpm. If you "hit" the throttle, you wouldn't notice anything. It was most apparent when "feathering" the thottle (eg, parking lot, creeping into the garage, that sort of thing). As it got worse, it crept into higher rpms. It got to where I was noticing a slight jerking of the car when loafing thru town (especially if a slight downgrade) at 30 mph with the engine turning over at 14 or 1500 rpm. I have an automatic and over 200k miles on the car now.

 

Commuter