restoring a 93 chevy c1500 with 4.3 stock tbi engine. engine was completely rebuild as well a trans.
engine starts, idles and revs fine,, hooked my autel obd2 scanner up to check things out, NO DTCs.
measured coolant temp sensor resistance/ temp corellation and within spec.. engine had new 195 F thermostat and new AC DELCO heated o2 sensor,. will not go into closed loop at idle, and havent driven it yet , as it needs tires badly.
I tried grounding the old O2 sensor signal wire to the ecm to ground and the scanner showed it went into closed loop, so I assumed it was the o2 sensor to be the problem. so we installed an new one and it still doesnt go into closed loop.. I have read that some trucks have closed loop timers on them, but cant find what they are.. truck sat at idle, at normal operating temp for abt 5 minutes, so I would think it would go closed loop by then,., but it didnt
the o2 sensor in in the manifold, and there is abt 6 inches of pipe left after the sensor, because the pipe was rusted thru so we chopped it off, to put a new exhaust system on it.,,
whats odd is the fuel trims are in control, short term 128, long around 16. o2 sensor is oscillating at around 450 to 510 MV
Truck doesnt run rich, or lean that I can tell. I unplugged the coolant temp sensor plug to see if the ecm would recognize a fault and throw a code, and it did.. the truck was throwing a knock sensor code, because when we rebuilt the engine, we got the wrong sensor,, out truck takes a 3900 ohm resisitance and they sold us a 100.000 ohm resistance knock sensor,, so we are very close to getting the truck running 100 percent perfect, just have to get it to go into closed loop.. any ideas appreciated.. I can give any scanner data requested.. thanks