Q My '01 Impala with the 3800 engine has 122,000 miles. For the last two months, it has began to surge rhythmically at about one-second intervals when accelerating from a stop sign or to maintain speed.
It does this whether in or out of cruise control and at speeds from 30 to 70 miles per hour. It doesn't do it consistently, but rather off and on. I can feel the surge in the seat of my pants, and I can see it on the tachometer, which will swing as much as 300 or 400 revolutions per minute. As soon as I stop accelerating, the surging stops.
I've used four bottles of fuel-system cleaner in as many tanks of regular gasoline, thinking it is a sticky fuel injector or maybe even a valve. This doesn't seem to help. Several mechanics think it still is a sticky fuel injector.
A A sticky or partially clogged fuel injector could well be the cause for this hesitation, or "chuggle," as it's often called. With an rpm change of 300 or 400, it could also be the torque converter clutch locking and unlocking for some reason.
A quick test for this would be to use your left foot to depress the brake pedal about half an inch -- not enough to actually engage the brakes, just enough to activate the brake switch -- and hold it at that point while you gently accelerate. If the chuggle disappears during this test, the problem is with the converter clutch or its "command" from the powertrain control module.
If this simple test doesn't change the symptom, the problem could be a faulty throttle-position sensor, restriction in the air filter or induction system, or a clogged injector. GM's special upper engine and injector cleaner may help clean a dirty injector and restore its performance.
Q My wife has a 2000 Dodge Intrepid. She overfilled the gas tank, and now we can't put gas in very fast. I would like to know what to do to remedy this problem.
A Overfilling the fuel tank may not be the cause of the slow-fill syndrome. My Alldata database pulled up technical service bulletin 14-001-03, dated January 2003, that deals with this symptom. Anytime the fuel tank will accept fuel only very slowly, it's a lack of proper venting during refueling. As fuel enters the tank, the volume of air displaced by the fuel must be vented. The first things to check are the tank vent lines and fill tube assembly for any blockage. In this case, the service bulletin also identifies the possibility of a stuck fuel tank control valve or a clogged leak detection pump filter.
