Used Ram Slippage
Q:I bought a used '99 Dodge Ram 1500 with about 69,000 miles on it. My truck shifts into a lower gear for no reason, even when I don't change the throttle position. It's sluggish when the truck goes into lockup and sounds like it's skipping and losing power when going up hills. The transmission has been checked by two different dealers and seems to be okay. I've tuned it up myself and replaced the plugs, wires, TPS, distributor cap, and rotor. I installed a new computer and cleaned and tested the fuel injectors. I've had two different Dodge dealers work on it, and they know something is wrong, but say they don't know what it is. Their computer shows only that the engine is running rich while idling.
A: It may be time to start with the basics, meaning the three common problems with the Magnum engine family. You've already replaced the ignition wires, and an important part of the job on the 5.2-liter V-8 is the proper routing of the wires to avoid a crossfire or ignition-wire induction. Then it'll require a technician to test for a vacuum leak at the intake manifold plenum gasket, which may produce symptoms ranging from a misfire to excessive oil consumption. The third item is reprogramming the Powertrain Control Module, which can eliminate problems with erratic shifting and power loss due to the lock-up torque converter engaging in third gear. The dealership technicians working on your Ram should be careful they haven't missed one of these items during diagnosis. Double-check everything, and if it all looks right, get the service manager at the Dodge dealer involved to stress the issue to help narrow down the problem.
Sensors Like To Be Clean
Q:The ABS on my '99 GMC Envoy has been coming on for no reason. When slowly coming to a stop, I can feel the ABS pulsating and making noise as if I'd hit the brakes hard enough to skid--but I'm stopping slowly and the road is fine. I took it to a brake shop, and it hasn't found any trouble codes.
A:Several older GMC and Chevy trucks have experienced low-speed anti-lock-brake operation under normal driving conditions. The cause is a corrosion buildup at the front-wheel speed-sensor mounting surfaces. The buildup increases the air gap between the sensor and the hub reluctor ring, which triggers the sensor with changing wheel speeds. The increased gap causes incorrect readings to be sent to the Electronic Brake Control Module, and the system reacts accordingly by varying hydraulic pressure to the wheel in question. The correction involves testing the voltage output from each sensor, removing the sensors, and cleaning the sensor mounting surface at each hub. This will decrease the air gap and bring the readings back within the correct voltage parameters. The sensors may need to be replaced if excessively distorted. This condition will not set off a diagnostic trouble code. Bring it into a GMC service department where they're more familiar with the problem, as opposed to an outside repair shop.