jeff
November 15th, 2004, 15:23
A buddy of mine has a problem with his Chevy... I told him RDC has some Chevy experts and he e-mailed me the problem and symptoms. Here's a copy/paste:
Hey Jeff,
Here's where I am with the Chevy. I have had an intermittent check engine light for a while and I bought a scanner to read the codes and to read the signals the computer is getting when the vehicle is operating. As you saw last Saturday, the truck loses power and sets the check engine light. The code is for O2 Sensor Low Voltage Bank 1 and O2 Sensor Low Voltage Bank 2 ( I think the codes are P0131 and P0151, but I can't remember for sure). When you drive the truck with the scanner hooked up, the O2 sensor voltage cycles between 0.1 to 0.9 volts at idle, and then drops to around 0.02 volts when you open the throttle. The fuel system also goes to open loop on both fuel systems. I stop the truck and turn the ignition off for a few seconds and then restart and drive the truck. After doing this a few times, the fuel system goes back to closed loop and the O2 sensors start to read between 0.1 and 0.9 volts again, and the truck runs fine with no power loss at any throttle setting. The TPS, IAT, MAP and ECT sensors are operating correctly. The MAF sensor seems to operate as it changes the air flow indication as the throttle is cycled. I checked the fuel pressure and it is 62 psi with the engine off, and drops to 57 with the engine on at idle. When you open the throttle rapidly with no load on the engine, the pressure jumps up to 62 psi. I have no way to check the fuel pressure when the engine is loaded. I checked the pump volume by opening the pressure relieve valve on the pressure gage and dumping the fuel into a container while the engine is running, and there is no detectable change in the engine. I talked to Nicole's dad last night and he has never really heard of the computers failing. His experience is that the problem is usually not with the computer. I have a new fuel filter so it should not be plugged yet. I also installed a new fuel injector assembly when I installed a remanufactured engine in October (the rear main seal was leaking on the old one and it had over 200K miles). I had the same check engine light before I installed the new engine and fuel injectors. Nicole's dad had a problem with a vehicle once where he was getting an intermittent loss of fuel to the carburetors and it turned out that he had a piece of debris in the fuel line that would occasionally move and partially block the line. I am thinking this may be my problem. I don't know where the restriction is, so I am planning to remove the fuel tank to check there first and replace the fuel pump and strainer at the same time in case the problem is there. I am then going to blow air through the open fuel lines before I put the fuel tank back in to make sure there is nothing in the lines. If this doesn't fix my problem, I don't know what I will do. If you have any ideas let me know. The truck is a '96 Chevy K1500 4x4 with a 5.7L Vortec. Thanks.
Jim
Aloha
Hey Jeff,
Here's where I am with the Chevy. I have had an intermittent check engine light for a while and I bought a scanner to read the codes and to read the signals the computer is getting when the vehicle is operating. As you saw last Saturday, the truck loses power and sets the check engine light. The code is for O2 Sensor Low Voltage Bank 1 and O2 Sensor Low Voltage Bank 2 ( I think the codes are P0131 and P0151, but I can't remember for sure). When you drive the truck with the scanner hooked up, the O2 sensor voltage cycles between 0.1 to 0.9 volts at idle, and then drops to around 0.02 volts when you open the throttle. The fuel system also goes to open loop on both fuel systems. I stop the truck and turn the ignition off for a few seconds and then restart and drive the truck. After doing this a few times, the fuel system goes back to closed loop and the O2 sensors start to read between 0.1 and 0.9 volts again, and the truck runs fine with no power loss at any throttle setting. The TPS, IAT, MAP and ECT sensors are operating correctly. The MAF sensor seems to operate as it changes the air flow indication as the throttle is cycled. I checked the fuel pressure and it is 62 psi with the engine off, and drops to 57 with the engine on at idle. When you open the throttle rapidly with no load on the engine, the pressure jumps up to 62 psi. I have no way to check the fuel pressure when the engine is loaded. I checked the pump volume by opening the pressure relieve valve on the pressure gage and dumping the fuel into a container while the engine is running, and there is no detectable change in the engine. I talked to Nicole's dad last night and he has never really heard of the computers failing. His experience is that the problem is usually not with the computer. I have a new fuel filter so it should not be plugged yet. I also installed a new fuel injector assembly when I installed a remanufactured engine in October (the rear main seal was leaking on the old one and it had over 200K miles). I had the same check engine light before I installed the new engine and fuel injectors. Nicole's dad had a problem with a vehicle once where he was getting an intermittent loss of fuel to the carburetors and it turned out that he had a piece of debris in the fuel line that would occasionally move and partially block the line. I am thinking this may be my problem. I don't know where the restriction is, so I am planning to remove the fuel tank to check there first and replace the fuel pump and strainer at the same time in case the problem is there. I am then going to blow air through the open fuel lines before I put the fuel tank back in to make sure there is nothing in the lines. If this doesn't fix my problem, I don't know what I will do. If you have any ideas let me know. The truck is a '96 Chevy K1500 4x4 with a 5.7L Vortec. Thanks.
Jim
Aloha