Flakey Fuel Pump?
Q: My 2000 Chevy Tahoe 4x4 has the 5.3-liter V-8 and 100,000 miles. It's beginning to develop an intermittent problem. When I drive it a short distance, say to the store, I come back out and the engine cranks and acts like it's going to start, but then it won't. It's almost like it isn't getting any gas. If I let it sit for 15 or 20 minutes, it'll start. This happens every couple days or so. I've changed the fuel filter, plugs, and wires. It was starting and running better than it had in quite a while; however, four days later, the problem came back. What I should check next?
A: A lot of things can cause an engine to intermittently crank but not start. It could be a fault with idle air control, a failure in the ignition system, or various types of fuel-delivery problems, to name a few. All systems should be inspected and tested by a qualified technician. The most common cause of this type of complaint is often a fuel-pressure issue--more than likely, it's the fuel pump itself. If you are the original owner of the vehicle and unaware of the fuel pump having been replaced previously, that's another clue. Many fuel pumps don't last 100,000 miles. However, there also could be a fault in the fuel-pump's electronic circuitry, such as a bad fuel-pump relay, or a missing signal from the powertrain control module that activates the pump circuit. A technician would probably use a scan tool to check for trouble codes, look for incorrect incoming data or outgoing commands, and then test the pressure with a fuel-pressure gauge. It should read between 55 and 62 psi with the ignition on and the engine off. The next time it happens, and you have a passenger on board, ask him to work the ignition while you remove the gas cap and listen for a hum from the fuel pump in the tank. You should hear it for a couple seconds when the ignition is turned on and continuously while cranking. This information may be helpful to a technician working on the job, especially if he's having difficulty duplicating the condition in the shop.
Earth-Quaking Trans
Q: I have a 2000 Chevy pickup with the 6.0-liter engine. Last year, when I was using it to tow my trailer, it was shifting rough. The dealership updated the computer calibration, and it seemed to run fine for a while, then it started to happen again, this time without the trailer. Now it's clunking in all gears, up and down. I was told I needed a new torque converter. Are there any other problems to consider before I spend the big money?
A: Let's not try to fix anything that isn't broken. Right now, you should focus on the shifting problem. I presume what you've described as a rough shift is a late and/or hard engagement. You know, almost snapping your neck back during a 1-2 or 2-3 upshift. Communication between vehicle owners and technicians can be misleading. That's part of the reason why a good long road test is so important when evaluating a transmission-related driveability concern. I'm bringing this up because harsh shifting is typically not a symptom of torque-converter failure. Usually there's a loss of power or poor acceleration, noise, vibration, shuddering, or a complete lack of engagement. The technician who diagnosed the condition may have found solid evidence that I'm not aware of to support the torque-converter replacement, or it could be a misdiagnosis. Harsh shifting can be caused by a number of hydraulic or electronic faults. If you're not sure about the converter replacement, get a second opinion from a qualified Chevrolet service department or specialty transmission shop.