Hydrocarbons Too High
Thread Starter
|
New User
Joined: Jan 2005
Posts: 2
Likes: 0
Hydrocarbons Too High
86 bronco 2 with 2.9 EFI - 240,000 miles
OK...I know...why not just shoot it and get a newer vehicle.
Well, it runs good, it just has a hard time passing the HC test.
CO test was never a problem. Pulled the trouble codes.
Codes present...21(Engine Coolant Temp Sensor), 24 (Air Charge Temp Sensor),
67 ((Neutral Drive Switch or Clutch Switch), 84 (EGR).
Whats been done...changed O2 sensor and put in new plugs. Distributor
and Ign Module were changed about 4-5 years ago.
So...my question is...What do you think would yield the most results in improving
the HC reading???
Jim
Mt Juliet
OK...I know...why not just shoot it and get a newer vehicle.
Well, it runs good, it just has a hard time passing the HC test.
CO test was never a problem. Pulled the trouble codes.
Codes present...21(Engine Coolant Temp Sensor), 24 (Air Charge Temp Sensor),
67 ((Neutral Drive Switch or Clutch Switch), 84 (EGR).
Whats been done...changed O2 sensor and put in new plugs. Distributor
and Ign Module were changed about 4-5 years ago.
So...my question is...What do you think would yield the most results in improving
the HC reading???
Jim
Mt Juliet
Post Fiend
Joined: Dec 2001
Posts: 10,562
Likes: 4
From: South Jersey
A bad ECT or ACT can cause a rich condition.....
PRE-DIAGNOSTIC INFORMATION
IAT/ECT Sensors
Engine coolant temperature must be greater than 10°C (50°F) to pass the KOEO Self-Test and greater than 82°C (180°F) to pass the KOER Self-Test. To accomplish this, the engine should be at normal operating temperature.
Ambient temperature should be above 10°C (50°F) to receive acceptable input from the Intake Air Temperature (IAT) sensor.
DA1 CHECK VREF CIRCUIT VOLTAGE AT THROTTLE POSITION SENSOR
Possible Causes:
-- Low engine coolant level.
-- Damaged harness connector.
-- Damaged sensor.
-- Ambient temperature below 10°C (50°F).
l Key off.
l Disconnect TP sensor.
l Key on, engine off.
l Measure voltage between VREF circuit and SIG RTN circuit at the TP sensor vehicle harness connector.
l Is voltage between 4.0 and 6.0 volts?
Yes
RECONNECT TP sensor. GO to «DA2».
No
REPAIR VREF circuit. RETURN to the Test Step in «Section 3», Symptom Charts, which sent you to this Pinpoint Test.
DA2 CHECK RESISTANCE OF TEMPERATURE SENSOR WITH ENGINE OFF
l Key off.
l Disconnect IAT or ECT sensor.
l Measure resistance between sensor signal circuit and SIG RTN circuit at the temperature sensor. Refer to the table in «Section 6», Reference Values for resistance specifications for IAT/ECT sensor.
l Is resistance within specification?
Yes
GO to «DA3».
No
REPLACE sensor. RECONNECT vehicle harness. RETURN to the Test Step in «Section 3», Symptom Charts, which sent you to this Pinpoint Test.
DA3 CHECK RESISTANCE OF TEMPERATURE SENSOR WITH ENGINE RUNNING
NOTE:
Engine may have cooled down. Always warm engine before taking ECT sensor resistance measurements. Check for open thermostat.
l Key off.
l IAT or ECT sensor disconnected.
l Run engine for two minutes at 2000 rpm.
l Measure resistance between sensor signal circuit and SIG RTN circuit at the temperature sensor. Refer to the table in «Section 6», Reference Values.
l Is resistance within specification?
Yes
GO to «DA4».
No
REPLACE sensor. RECONNECT vehicle harness. RETURN to the Test Step in «Section 3», Symptom Charts, which sent you to this Pinpoint Test.
DA4 CHECK RESISTANCE OF SENSOR SIGNAL AND SIG RTN CIRCUITS
l Key off.
l IAT or ECT sensor disconnected.
l Disconnect Powertrain Control Module (PCM). Inspect for damaged or pushed out pins, corrosion, loose wires. Service as necessary.
l Install breakout box. Leave PCM disconnected.
l Measure resistance between sensor signal circuit at the temperature sensor vehicle harness connector and ECT or IAT at the breakout box.
l Measure resistance between SIG RTN circuit at the temperature sensor vehicle harness connector and SIG RTN at the breakout box.
l Is each resistance less than 5.0 ohms?
Yes
GO to «DA5».
No
SERVICE open circuits. REMOVE breakout box. RECONNECT all components. RETURN to the Test Step in «Section 3», Symptom Charts, which sent you to this Pinpoint Test.
DA5 CHECK FOR SENSOR SIGNAL SHORTED TO VREF
l Key off.
l IAT or ECT sensor disconnected.
l Disconnect PCM. Inspect for damaged or pushed out pins, corrosion, loose wires. Service as necessary.
l Install breakout box. Leave PCM disconnected.
l Measure resistance between sensor signal circuit ECT or IAT and VREF at the breakout box.
l Is each resistance greater than 10,000 ohms?
Yes
GO to «DA6».
No
REMOVE breakout box. RECONNECT all components. LOCATE and SERVICE short to VREF. RETURN to the Test Step in «Section 3», Symptom Charts, which sent you to this Pinpoint Test.
DA6 CHECK TEMPERATURE SENSOR SIGNAL CIRCUIT FOR SHORT TO GROUND
l Key off.
l IAT or ECT sensor disconnected.
l Disconnect Powertrain Control Module (PCM). Inspect for damaged or pushed out pins, corrosion, loose wires. Service as necessary.
l Install breakout box. Leave PCM disconnected.
l Measure resistance between ECT or IAT and PWR GND at the breakout box.
l Is each resistance greater than 10,000 ohms?
Yes
RETURN to the Test Step in «Section 3», Symptom Charts, which sent you to this Pinpoint Test.
No
SERVICE short circuit. REMOVE breakout box. RECONNECT all components. RETURN to the Test Step in «Section 3», Symptom Charts, which sent you to this Pinpoint Test.
PRE-DIAGNOSTIC INFORMATION
IAT/ECT Sensors
Engine coolant temperature must be greater than 10°C (50°F) to pass the KOEO Self-Test and greater than 82°C (180°F) to pass the KOER Self-Test. To accomplish this, the engine should be at normal operating temperature.
Ambient temperature should be above 10°C (50°F) to receive acceptable input from the Intake Air Temperature (IAT) sensor.
DA1 CHECK VREF CIRCUIT VOLTAGE AT THROTTLE POSITION SENSOR
Possible Causes:
-- Low engine coolant level.
-- Damaged harness connector.
-- Damaged sensor.
-- Ambient temperature below 10°C (50°F).
l Key off.
l Disconnect TP sensor.
l Key on, engine off.
l Measure voltage between VREF circuit and SIG RTN circuit at the TP sensor vehicle harness connector.
l Is voltage between 4.0 and 6.0 volts?
Yes
RECONNECT TP sensor. GO to «DA2».
No
REPAIR VREF circuit. RETURN to the Test Step in «Section 3», Symptom Charts, which sent you to this Pinpoint Test.
DA2 CHECK RESISTANCE OF TEMPERATURE SENSOR WITH ENGINE OFF
l Key off.
l Disconnect IAT or ECT sensor.
l Measure resistance between sensor signal circuit and SIG RTN circuit at the temperature sensor. Refer to the table in «Section 6», Reference Values for resistance specifications for IAT/ECT sensor.
l Is resistance within specification?
Yes
GO to «DA3».
No
REPLACE sensor. RECONNECT vehicle harness. RETURN to the Test Step in «Section 3», Symptom Charts, which sent you to this Pinpoint Test.
DA3 CHECK RESISTANCE OF TEMPERATURE SENSOR WITH ENGINE RUNNING
NOTE:
Engine may have cooled down. Always warm engine before taking ECT sensor resistance measurements. Check for open thermostat.
l Key off.
l IAT or ECT sensor disconnected.
l Run engine for two minutes at 2000 rpm.
l Measure resistance between sensor signal circuit and SIG RTN circuit at the temperature sensor. Refer to the table in «Section 6», Reference Values.
l Is resistance within specification?
Yes
GO to «DA4».
No
REPLACE sensor. RECONNECT vehicle harness. RETURN to the Test Step in «Section 3», Symptom Charts, which sent you to this Pinpoint Test.
DA4 CHECK RESISTANCE OF SENSOR SIGNAL AND SIG RTN CIRCUITS
l Key off.
l IAT or ECT sensor disconnected.
l Disconnect Powertrain Control Module (PCM). Inspect for damaged or pushed out pins, corrosion, loose wires. Service as necessary.
l Install breakout box. Leave PCM disconnected.
l Measure resistance between sensor signal circuit at the temperature sensor vehicle harness connector and ECT or IAT at the breakout box.
l Measure resistance between SIG RTN circuit at the temperature sensor vehicle harness connector and SIG RTN at the breakout box.
l Is each resistance less than 5.0 ohms?
Yes
GO to «DA5».
No
SERVICE open circuits. REMOVE breakout box. RECONNECT all components. RETURN to the Test Step in «Section 3», Symptom Charts, which sent you to this Pinpoint Test.
DA5 CHECK FOR SENSOR SIGNAL SHORTED TO VREF
l Key off.
l IAT or ECT sensor disconnected.
l Disconnect PCM. Inspect for damaged or pushed out pins, corrosion, loose wires. Service as necessary.
l Install breakout box. Leave PCM disconnected.
l Measure resistance between sensor signal circuit ECT or IAT and VREF at the breakout box.
l Is each resistance greater than 10,000 ohms?
Yes
GO to «DA6».
No
REMOVE breakout box. RECONNECT all components. LOCATE and SERVICE short to VREF. RETURN to the Test Step in «Section 3», Symptom Charts, which sent you to this Pinpoint Test.
DA6 CHECK TEMPERATURE SENSOR SIGNAL CIRCUIT FOR SHORT TO GROUND
l Key off.
l IAT or ECT sensor disconnected.
l Disconnect Powertrain Control Module (PCM). Inspect for damaged or pushed out pins, corrosion, loose wires. Service as necessary.
l Install breakout box. Leave PCM disconnected.
l Measure resistance between ECT or IAT and PWR GND at the breakout box.
l Is each resistance greater than 10,000 ohms?
Yes
RETURN to the Test Step in «Section 3», Symptom Charts, which sent you to this Pinpoint Test.
No
SERVICE short circuit. REMOVE breakout box. RECONNECT all components. RETURN to the Test Step in «Section 3», Symptom Charts, which sent you to this Pinpoint Test.
