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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 380 (Engine Controls - Trouble Shooting - No Codes - 3.4L) >> Symptoms >> Hesitation, Sag Or Stumble >> Sensor/System

Hesitation, Sag Or Stumble: Sensor/System

WARNING: This page is about a different car, the 2003 Pontiac Grand Am, 2003 Oldsmobile Alero, 2003 Chevrolet Monte Carlo, and 2003 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: Contamination of the oxygen sensor can result from the use of an inappropriate RTV sealant (not oxygen sensor safe) or excessive engine coolant or oil consumption. Remove the HO2S and visually inspect the portion of the sensor exposed to the exhaust stream to check for contamination. If contaminated, the portion of the sensor exposed to the exhaust stream will have a White powdery coating. Silicone contamination causes a high but false HO2S signal voltage (rich exhaust indication). The Powertrain Control Module (PCM) will then reduce the amount of fuel delivered to the engine, causing a severe driveability problem. Eliminate the source of contamination before replacing the oxygen sensor.
  1. Monitor the Heated Oxygen Sensors (HO2S). The HO2Ss should respond quickly to different throttle positions. If not, inspect the HO2S for silicone or other contaminants from fuel or use of improper RTV sealant. The sensors may have a White powdery coating. Silicone contamination causes a high but false HO2S signal voltage, rich exhaust indication. The PCM will reduce the amount of fuel delivered to the engine, causing a severe driveability problem.
  2. Monitor the 24X crank sensor and the CMP sensor signal present parameters on the scan tool. If both are not responding, test the sensor feed circuit. Both sensors use a separate feed circuit but are internally connected to power. Check all CKP A and CMP sensor circuits for intermittents. Go to INTERMITTENTS  .
  3. Monitor the 3X crank sensor parameter on the scan tool. If the 3X crank sensor parameter is not responding, inspect the CKP sensor "B" and circuits for intermittents. Inspect the Ignition Control (IC) circuit, IC timing control circuit, low resolution engine speed signal circuit and the 3X low reference circuit for intermittents. Go to INTERMITTENTS  . If these circuits become open or shorted they may not set a Diagnostic Trouble Code (DTC) immediately, but are capable of causing driveability complaints.
  4. Check the CKP sensor "B" for an internal short. Go toELECTRONIC IGNITION SYSTEM DIAGNOSIS under IGNITION SYSTEMS in SYSTEM & COMPONENT TESTING - 3.4L ALERO, GRAND AM, IMPALA & MONTE CARLO article.
  5. Inspect the Throttle Position (TP) sensor and related wiring.
  6. Inspect the Mass Airflow (MAF) sensor and related wiring. Inspect the air intake ducts for being collapsed, damaged areas, looseness, improper installation, or leaking especially between the MAF sensor and the throttle body.
  7. Check the Exhaust Gas Recirculation (EGR) system for proper operation.
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