Probe V6-182 3.0L (1990)
Thermostat Gasket: Technical Service Bulletins
Engine - Rough Idle During Warm Up
Article No. 91-22-4
10/30/91
IDLE - ROUGH - 3.0L - LX MODELS
FORD:
1990-92 PROBE
ISSUE:
A rough idle may occur during engine warm-up and at normal operating temperatures. It may also occur at idle after a long cruise at highway
speeds. This condition may be caused by a variety of engine ignition or fuel sources, including a faulty thermostat.
ACTION:
Inspect the fuel system/ignition components and perform the necessary rough idle diagnostic routines and, if necessary, replace the
thermostat and gasket. Refer to the following procedure for service details.
INSPECTION AND DIAGNOSIS
1.
Request the customer to help you complete the Customer Information Worksheet as outlined in Section 2A-2, Page 2, of the 1992 Powertrain
Control Engine/Emissions Diagnosis Manual. This worksheet will help the technician fully understand the concern.
2.
Prior to performing any inspections or repairs, review the following items that could contribute to a poor quality or rough idle condition.
^
Refer to the 1991 Engine/Emissions Diagnosis Manual, Section 2 - Page 2A-10, and review the Diagnosis Routines for "Rough Idle".
^
Check the fuel system pressure(s)/components.
^
Refer to TSB Article 91-10-9 for throttle body cleaning procedures and idle speed adjustments.
^
Check for incorrect level parts which might have been installed from any previous repairs. Also, look for any incomplete or improper
adjustments.
The engine coolant thermostat could cause a poor idle quality if a stabilized temperature of 197~ F (92~ C) or higher is not maintained. If the engine
coolant is a few degrees too cool, the ECT (Engine Coolant Temperature Sensor) will register a slightly higher voltage. About 0.57 volts is the ECT
value for stabilized engine temperature.
If visual inspections and the diagnostic routines did not pinpoint the cause of the concern, proceed with the following service action.
SERVICE PROCEDURE
1.
Check the engine coolant level and fill to the correct level if needed.
2.
Attach a fuel pressure test gauge to the fuel rail and monitor during the tests.
a.
Refer to the 1992 Probe Service Manual, Section 9A pages 25-28, for fuel pressure test gauge installation, pressure specifications and test
procedures.
b.
Resolve fuel pump/system concerns as needed.
3.
Attach a digital volt ohmmeter to the ECT sensor by connecting the test leads to the ECT sensor wire harness connector.
CAUTION: DO NOT PUNCTURE OR CUT THE ECT SENSOR WIRES WHEN CONNECTING THE TEST LEADS. DO NOT DISCONNECT
THE ECT WIRE HARNESS FROM THE ECT FOR THIS TEST, RUN THE LEADS AND METER INSIDE THE VEHICLE.
4.
Perform Self Test, Key On Engine Off (KOEO), record any fault codes and resolve prior to proceeding with Step 5.
NOTE: DO NOT ATTACH A BREAK OUT BOX (B.O.B.) OR AN ECC IV MONITOR TO THE EEC WIRE HARNESS. DISCONNECTING THE
ECA WILL ERASE THE DRIVE MEMORY AND CAUSE THE RELEARNING (ADAPTIVE STRATEGY) TO "HIDE" THE DRIVE
CONCERNS.
5.
Start the engine and record the ECT voltage.
a.
Allow the engine to idle until the ECT voltage has stabilized at about .5 volts or less (200~ F/93~ C or higher).
b.
Record the ECT voltage.
