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Car expert, ASE Certified Technician
Category: Car
Satisfied Customers: 10370
Experience:  ASE MASTER TECHNICIAN,30 YRS EXPERIENCE
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infinity QX4: it stop at stop sign and red light

Resolved Question:

my car infinity QX4, when it stop at stop sign and red light . some time the engine it stop ,I must retart let it go.why?
Submitted: 7 years ago.
Category: Car
Expert:  Car expert replied 7 years ago.

HI I CAN HELP, THIS IS MOST LIKELY A BAD DISTRIBUTOR BUT HERE ARE A FEW TESTS WE SHOULD DO FIRST,

 

Customer Concern:The engine idles fine but touch the throttle and it dies. Has good fuel pressure.
Tests/Procedures:1. Check the strength of the spark at the spark plugs with a round blade screwdriver. Look for a good 1/2 inch minimum nice strong blue spark.

2. Put a timing light on it and verify ignition is firing consistently in time Specification is 15 degrees Before Top Dead Center (BTDC) at warm idle with the brown connector of the Throttle Position Sensor (TPS) disconnected.

3. See if the engine responds to supplemental fuel.

4. Check long and short term fuel trims on the scanner to see if the system is in proper fuel control - look for 0% plus or minus 5% to be normal.

5. Check the Mass Airflow (MAF) sensor grams/second - specification is 3.3-4.8 grams at warm idle and 12.0-14.9 grams at 2500 RPM no load.

6. Check calculated engine load - specification is 18.5-26.0% at warm idle and 18.0-21.0% at 2500 RPM no load.

7. Check engine vacuum.

8. Check camshaft timing/timing belt as necessary.

9. Check for a clear exhaust.

10. Check the scanner for throttle %. Specification is 0% closed throttle and 80% at Wide Open Throttle (WOT).

11. Check the Throttle Position Sensor (TPS) sweep voltage on the White wire in the brown connector with the connector plugged in and back probing. Look for about 0.3-0.5 volts closed throttle and about 4.0 volts at WOT.

12. Check the idle switch voltage on the Orange/White wire in the gray connector at the TPS. Look for 12 volts (battery voltage) closed throttle and near 0 volts just off idle.
Potential Causes:Distributor
Exhaust System
Mass Air Flow (MAF) Sensor
Weak Spark
Timing Belt

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