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An error has been detected in by the engine management system causing the CEL to indicae and this error is affecting the erratic rpm.
You would need to retrieve the trouble code to understand what is causing the problem.
Being a pre OBD-II model I do not know if Autozone is able to perform a free scan for you. Try and see if they can do it for you and let me know the exact trouble code so I can get the required information to help you resolve the problem.
Alternatively you can try retrieving codes with a non scan method as outlined below.
RETRIEVING CODES (NON-SCAN)
Inserting jumper wire into test and ground terminals of DLC connector with engine running will cause fuel injected vehicles to enter field service mode. Flashes of SERVICE ENGINE SOON light will not indicate codes if this is done.
Turn ignition on.
1. DO NOT start engine. SERVICE ENGINE SOON light should glow. Locate Data Link Connector (DLC) attached to control module wiring harness. Most DLC connectors are located under dash on driver side of vehicle. For exact location of DLC, see COMPONENT LOCATIONS in I - SYS/COMP TESTS article in this section. Insert jumper wire from terminal "B" (diagnostic test terminal) to terminal "A" (ground) of DLC connector. See Fig. 1
2. SERVICE ENGINE SOON light should begin to flash codes. Each code will be repeated 3 times. To exit diagnostic mode, turn ignition off and remove jumper wire from DLC connector.
READING TROUBLE CODES
Only general information (hard and intermittent) codes may be retrieved using non-scan method. Malfunction history information flags and codes can be retrieved only by using a scan tester. Control module stores component failure information under a related trouble code which can be recalled for diagnosis and repair. Trouble codes may be read by counting flashes of SERVICE ENGINE SOON light or by reading digital display on a scan tester. Scan tester is faster to use, more accurate and capable of reading information which otherwise would necessitate testing individual control module and sensor/solenoid connector terminals using a digital voltmeter.
When using most scan testers, a time delay exists between serial data updates. For instantaneous response, a digital voltmeter must be used.
If scan tester is not available, reading flashes of SERVICE ENGINE SOON light is possible by grounding diagnostic test terminal "B" of DLC with ignition on and engine off. See Fig. 1. For example, "FLASH, FLASH, pause, FLASH, longer pause" identifies Code 21. First series of flashes is first digit of trouble code. Second series of flashes is second digit of trouble code. Trouble codes are displayed starting with lowest numbered code. Each code is displayed 3 times. Codes will continue to repeat as long as DLC test terminal is grounded.
Trouble codes will be recorded at various operating times. Some codes require operation of that sensor or switch for 5 seconds; others require operation for 5 minutes or longer at normal operating temperature, vehicle speed and load. Therefore, some codes may not set in a service bay operational mode and may require road testing vehicle in order to duplicate condition under which code will set.
Sunday, January 17th, 2010 AT 7:27 AM