Poor Power/Service Engine Soon Light
 

I have a 1999 Chevy Blazer LT, V6, 2WD, 127000 miles. I have had problems recently with poor power & ruff idling. After replacing the water pump and thermostat due to sudden overheating these symptoms where worse but also Service Engine Soon light at times. The engine died soon after starting one morning but started right up. My mechanic tuned it up with new plugs, wires, rotary cap & button & cleared the codes. He reports the pressure from the fuel pump is good.
The symptoms are a little better & the Service Engine Soon light started coming again after a day. The alternator squeaks a little. The fuel gauge has never worked during the year that I have owned it. I have $700 invested in this mechanic for these problems. At least it doesn't overheat anymore. I mentioned the MAF sensor to which he said: "I don't do much with sensors."
Obviously I need another mechanic but any ideas as to the problem with this truck would help.

You'll have to let us know what the service engine light code(s) were.

Definitely let us know what the specific trouble codes are/were (Pxxxx).

Aside from that, you can clean the throttle body, paying particular attention to the IAC valve and bore. Clean the EGR valve. And clean the MAF sensor.

These are things you should be able to do while you locate a mechanic that understands modern vehicles.

The codes are:
P0171B Fuel Trim Lean Bank 1,
P0174B Fuel Trim Lean Bank 2,
P0463C Fuel Level Sensor Circuit High Voltage,
P1107C Manifold Absolute Pressure Sensor Voltage Intermittently Low,
P1345A Crank Position/Cam Position Sensor Correlation.

These are codes that my mechanic retrieved from my vehicle today. When I checked on his progress this afternoon, he had replaced the MAP sensor which he says was in very bad shape & was cleaning the MAF sensor. He cleaned the throttle body last week.

P0171 - Fuel Trim System Lean Bank 1
P0174 - Fuel Trim System Lean Bank 2
P0463 - Fuel Level Sensor Circuit High Voltage
P1107 - MAP Sensor Circuit Intermittent Low Voltage
P1345 - Crankshaft Position [CKP] Camshaft Position [CMP] Correlation

You should start by taking a look at all of the schematics for each of these codes and seeing if there is any common wiring (grounds or power sources).