QuestionI own a 90 S-10 Blazer 4x4 4.3 with a newer motor. Vehicle has 144000 however motor has only 120000. Over the last couple weeks I have begun to notice it has lost power, seems to idle rather low and almost sounds like it is starving for fuel. Exhaust seems to sputter like only 5 cylinders are firing. I have already changed plugs, wires, fuel filter, air filter, MAP sensor, oil and filter, and had dist checked. runs great cold but seems to not only lack power when warm, but is smoking black from tailpipe indicating fuel problem. A strong odor of rich exhaust is present. I am to check and change fuel pressure reg as well as O2 sensor but our garages in this area for diagnostic testing are very high priced. I have tried trouble codes at home with absolutely NO codes other than 12 (all clear). Other than possibly having to also change PCV,EGR,TPS,or Idle Control Sensor, Any advice you could give would be extremely helpful. Thank you.
AnswerHi Ryan,
I am thinking that rather than starving for fuel, it is flooding.
When the engine is cold, many of the sensor inputs are not used, and the injectors use a default setting, with the throttle plate only changing air flow.
It is possible one of your sensors is bad, and when the engine reaches operating temp, and goes into closed loop, the faulty sensor causes too much fuel.
I hate just changing parts, but since you don't get any fault codes, it would seem like the oxygen sensor isn't sending a rich reading to the ecm, even with the black smoke and rich smell.
Just using that logic, the oxygen sensor would seem to be the culprit.
A scan tool connected can tell what kind of readings it is sending.
Have you ever used silicone sealer anywhere in the intake system? Silicone, even a tiny amount, will ruin an oxygen sensor, unless it is specifically meant for oxygen sensor systems.
Fuel pressure is something else I would want to check. I believe you have throttle body injection, so the pressure should be 12 PSI with the engine running.
Van
