Service slants

Motor,  Sep 2003  by Savasta, Bob

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Chrysler

Front end noise. Owners of 2001-03 Sebring and Stratus models may complain of an intermittent popping or clunking sound coming from the front end of the vehicle. According to Chrysler, the noise occurs most frequently on road surfaces that cause the body to twist, or while the driver turns the steering wheel left and right with the gearshift lever in Park and the engine idling. Excess movement at the shock tower/wheelhouse interface is the likely cause of the ruckus.

Try to duplicate the symptoms by selecting a road that will result in the twisting of the cars body structure. If that's not possible, start the engine and turn the steering wheel 90[degrees], first to the left, then quickly back to the right. If the popping or clunking noise becomes obvious, get the car up in the air and remove both front wheels, followed by the wheel well splash shields. Working from the right side of the vehicle, drill two 17/64-inch holes into the wet plenum in the areas shown in the illustration. Next, coat the bare metal surfaces with a good corrosion inhibitor, then install two large rivets (Part No. 06033864) into the holes you drilled. That'll prevent the movement in the wheelhouse that causes the noise. Reinstall the splash shield and front wheel, then repeat the drilling exercise on the left side of the vehicle, once again using the illustration as a guide for the rivet location.

GM Truck

Multiple driveability concerns. An owner of a 2002 Chevy TrailBlazer, GMC Envoy or Olds Bravada with the 4.2L inline Six (VIN S) may come into your shop one day complaining of multiple but unrelated driveability concerns. The comments you're likely to hear are idle fluctuation on the first startup following an overnight soak at higher altitudes, hesitation on acceleration or delayed 1-2 upshifts with the throttle opened less than 25% and the engine cool.

Actually, all these problems do have something in common-the need for a PCM reprogramming to correct them. The calibration you're looking for can be found in software update TIS 2.5/2003 or later, which became available on 2/22/03. Make a note of the software revision for future reference.

Ford

Erratic EATC system operation. According to Ford, the electronic automatic temperature control (EATC) systems used on some of its 1999-2000 cars and light trucks (full list below) can act erratically at times. Among the customer complaints you're likely to hear are that the blower motor stays at high speed regardless of the temperature setting, the system can't maintain a set point and/or the system initially holds a set point but eventually loses it toward the cooler side of the temperature scale. All of these symptoms are the result of either a loosely mounted in-car temperature sensor or a sensor with a kinked, cut or disconnected hose. The latter cuts down or eliminates the aspiration needed for the sensor to adequately maintain a stable temperature.

Ford points out that a temp sensor needs to be firmly planted against the dash panel. If it isn't, a gap forms in the sensor-to-dash panel seal, which allows warm air from underneath the instrument panel to be drawn across the sensor. This affects the sensor's ability to "read" the true cabin temperature and typically results in a system that either can't hold a set point or cools too enthusiastically.

Most in-car sensors are mounted to the dash with two pins. Make sure the sensor is firmly engaged in these pins by pressing down firmly. If the temp sensor keeps moving away from the dash, either the harness pins are worn or the receptacles in the sensor are too wide. Replace the affected part as necessary.

Note that the temp sensors used on light trucks are mounted to the instrument panel using special fasteners. On these applications, it's okay for a gap to form between the fasteners, so long as it's positioned horizontally in relation to the panel. If it's vertical, the sensor will require greater pressure to seat against the instrument panel. Reindex the sensor as required.

To check for proper sensor aspiration, cut a 1-inch-square piece of tissue paper (don't use a paper towel or napkin; they're too heavy). Next, set the blower motor to High and the mode control to Panel or Vent while placing the piece of tissue over the aspirator grille opening. If adequate aspiration (suction) is available to the sensor, the tissue should stick to the grille. Now lower the fan speed a bit. The tissue paper should remain firmly planted on the grille. Finally, shut the blower motor down. The tissue paper should fall off. If the paper dislodges from the grille with the blower motor at any setting except Off, start searching for a kinked, cut or disconnected aspirator hose.

One more point: Some EATC-equipped vehicles still use an old-fashioned coolant control valve. This valve has to function properly for the system to maintain an accurate set. So check it for leakage or binding. Also inspect its vacuum hoses for kinks or leaks. Replace the valve or hoses as necessary.