Join Date: Aug 2009
Location: Cleveland, OH
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Tune up might be ok and really it's due for one, but I'm curious about what would happen if you resolved all of your MIL / trouble codes before you started disrupting the ever-so-touchiness of a high mileage engine. I've learned the hard way, at this stage in the game especially with so many miles, if you don't know 100% something is bad, don't even touch it.
If you decide to do a tuneup, replace anything you have with AC Delco if you can. Call a Chevy dealer for the most recent part numbers if need be. These discount parts stores aren't always the best place to get plug part numbers, because their computers are set up to tell you basically any plug that will screw into the head will be fine for your car, which I can tell you, is basically not the case. If you use anything but AC Delco, especially with the plugs, you may end up making it run even worse. Can you get to the upstream 02 sensor with an 02 sensor socket? I know they sometimes have them for rent at the parts store. But I wonder, if you're not getting a MIL indicator from the upstream 02, why do you think it's going bad? Is it because it's not giving you the right measurements in the datastream on the scanner? Is there a pending code? I wouldn't touch any sensor unless it's either giving you a code or a pending code, or it's not giving good readings in the datastream.
I believe your last item in the list could be worth looking into, I could be wrong of course, but read on. Your engine temperature matters to the fuel injection system. The PCM must always be getting an accurate reading from the temp sensor. If the thermostat is bad, replace that, too, or you will overcool or overheat depending if it's stuck open or closed. The engine should be running at the right temp, and providing the right temp readings to the PCM. The temp sensor works with the throttle body, PCM, and fuel injection system to provide the right lean/rich mixture of fuel to the engine. Back in the day, we used to call these chokes, but those don't exist anymore, Lol. I can't be too sure, but I think the temperature sensor tells the PCM when the car is warm, and then the PCM works with the fuel injection system to back down the richness. I'd make sure you're in closed loop mode after warm up on the scanner in the datastream - if the car is at full temp, and you're in open loop mode, then your system is isn't recognizing the engine has warmed up properly - if you're not in closed loop mode after warmup, then the engine/PCM is being tricked into thinking it's in warm up mode, and will use more gas. And, of course, if the datastream isn't reporting a temperature, then that tells you the sensor is bad, and needs replaced. Could that be part of the problem?
Last edited by jrd0304; 07-13-2012 at 05:45 AM.