Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSBUICK1999REGAL LSREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROL SYSTEM - TESTS W/CODES - DTC P0205-P0351DTC P0301DTC P0301, P0302, P0303 OR P0304: SPECIFIC CYLINDER MISFIRE DETECTED (1.9L SATURN)DIAGNOSTIC PROCEDURES
1999 Buick Regal LS
Diagnostic Procedures
1999 Buick Regal LSSECTION Diagnostic Procedures
- Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS INTRODUCTION article. After performing OBD system check, go to next step.
- Check for grounded/arching ignition wires. Repair or replace as necessary. If wires are okay, go to next step.
- Based on specific misfire DTC set, remove that affected cylinder's spark plug wire. Connect a spark tester to spark plug wire. Test for spark. If spark is consistent, go to next step. If spark is not consistent, check for faulty wire and/or coil pack. See DIAGNOSTIC AIDS .
- Remove spark plug from affected cylinder. Check spark plug gap (.060 in). Replace defective spark plug. If spark plug is okay, go to next step.
- Perform injector balance test. Use scan tool to pulse each injector and note fuel pressure drop. Re-prime fuel rail after each cylinder is tested. See appropriate BASIC DIAGNOSTIC PROCEDURES article. If pressure drop is consistent (1.5 psi), go to next step. If pressure is not consistent, go to step 7.
- Perform compression test on misfiring cylinder. Normal compression is 185-205 psi (13-14 kg/cm2 ). If compression is okay, replace spark plug(s). If compression is not okay, check for internal mechanical engine problem. Repair as necessary.
- Check injector resistance. Resistance should be 12 ohms. If resistance is as specified, check for stuck injector pintle valve or clogged injector. Clean or replace injector. If resistance is not as specified, replace injector and retest engine.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.