I have a 92 Chevy K-1500 truck (VIN #2GCEK19K3N1114936 with a 5.7 L engine, AC 700R4 non-electronic transmission) that is driving me completely crazy. The problem is that on some days, the truck runs 150 percent, and on others, it won’t get out of its own way. The weather and/or temperature have no effect on this condition. The valves ping, and the scanner shows a knock condition. I have tried everything! I have replaced everything from the computer/EPROM to the fuel injectors, including the fuel pump, filter, coolant temp sensor, MAP, TPS, computer, PROM, new injectors, intake and TBI gaskets, IAC motor, new MSD distributor, ignition coil, O2 sensor, EGR valve, alternator, battery, knock sensor, knock sensor module, fuel pump relay, park neutral switch, transmission and converter, new oil pump, thermostat, radiator, water pump, (the vehicle does not overheat). I removed the cat and installed 3-inch Flowmaster exhaust system; performed a full tune-up; and rebuilt the TBI.Also, sometimes at idle, the engine feels like it skips a beat. The motor is very clean and quiet, and no engine light is on. Nothing has worked. I even had the transmission rebuilt and a new GM converter installed. I took a compression test, and the lowest cylinder was 165 psi; the highest was 177.The truck has 165,000 miles and is very clean, so I would like to keep it. Please help me if you can; it is greatly appreciated. Thanks.
Harry Ulrich, Brockton, PA
Dear Harry:
OK, you win. There is nothing left to replace. Now let’s try another approach. The key symptom here is that the engine is pinging when the loss of power occurs and the scan tool displays a knock condition. This indicates that the engine management system is retarding the timing based on the knock signal. This of course will reduce power. Now the question is “why is it pinging?” Basically, pinging is the result of abnormally high combustion chamber temperatures. This could be the result of coolant system malfunctions, overly advanced ignition timing, lean mixtures, excessively high intake air temperatures, carbon deposits and/or EGR system malfunctions.You state that the cooling system is in good shape and the EGR was replaced, but is the EGR system working properly?
In order to pin this down to one area, let’s hook up the scan tool and set it up to read datastream and drive the vehicle until the condition occurs. If your scan tool is capable of recording a movie, set it up to do so at this point.What you are looking for is an indication of a lean condition when the symptoms occur. This will show up as low oxygen sensor voltage or high integrator readings. If you find the system is lean, you should test fuel pressure and volume while the vehicle is malfunctioning. Because this condition is sporadic, I suspect your problem may be the result of intermittent or open circuits caused by corrosion or insufficient contact of a harness connector. Remove the ECM connectors and check all female pin connectors for a snug fit with a #62 drill bit (0.037 inch). Pay close attention to the tan wire at D6. This is the oxygen sensor ground and has been a source of problems with this vehicle.
