DRIVEABILITY & EMISSION-6000 MANUAL SECTION 6E3-B SYMPTOMS

Subject section was not included in the 1986 Pontiac 6000 Service Manual.

Please update your service manual with this information.

SECTION B SYMPTOMS

BeforeStarting................................. Page B-2 Intermittents.................................. Page B-2 Hard Start..................................... Page B-3 Hesitation, Sag, Stumble....................... Page B-3 Surges and/or Chuggle.......................... Page B-4 Lack of Power, Sluggish, or Spongy............. Page B-4 Detonation/Spark Knock......................... Page B-5 Cuts Out, Misses............................... Page B-5 Backfire ..................................... Page B-6 Poor Fuel Economy............................. Page B-6 Dieseling, Run-On ............................ Page B-6 Rough, Unstable, or incorrect ldle, Stalling... Page B-7 Excessive Exhaust Emissions (Odors) .......... Page B-7

SECTION B SYMPTOMS

BEFORE STARTING

Before using this section you should have performed the DIAGNOSTIC CIRCUIT CHECK and found out that:

1. The ECM and "SERVICE ENGINE SOON" light are operating. 2. There are no trouble codes stored, or there is a trouble code but no "SERVICE ENGINE SOON" light.

3. The fuel control system is operating OK (by performing Field Service Mode Check).

Verify the customer complaint, and locate the correct SYMPTOM below. Check the items indicated under that symptom.

If the ENGINE CRANKS BUT WILL NOT RUN, see CHART A-3.

Several of the symptom procedures below call for a Careful Visual Check. This check should include:

ECM grounds for being clean and tight

Vacuum hoses for splits, kinks, and proper connections, as shown on Emission Control Information label.

Air leaks at throttle body mounting and intake manifold.

Air leaks between MAF sensor and throttle body.

Ignition wires for cracking, hardness, proper routing, and carbon tracking.

Wiring for proper connections, pinches, and cuts.

The importance of this step cannot be stressed too strongly - it can lead to correcting a problem without further checks and can save valuable time.

INTERMITTENTS

Problem may ormay notturn"on"the"SERVICE ENGINE SOON"light, or store acode.

DO NOT use the Trouble Code Charts in Section A for intermittent problems. The fault must be present to locate the problem.If a fault is intermittent, use of Trouble Code Charts may result in replacement of good parts.

Most intermittent problems are caused by faulty electrical connections or wiring. Perform careful check as described at start of Section B. Check for:

Poor mating of the connector halves, or terminals not fully seated in the connector body (backed out).

Improperly formed or damaged terminals. All connector terminals in problem circuit should be carefully reformed to increase contact tension. Poor terminal to wire connection. This requires removing the terminal from the connector body to check. See Introduction to Section 6E.

If a visual check does not find the cause of the problem, the car can be driven with a voltmeter connected to a suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. If the wiring and connectors check OK and a Trouble Code was stored for a circuit having a sensor, except for codes 44 and 45, substitute a known good sensor and recheck.

An intermittent "SERVICE ENGINE SOON" light with no stored code may be caused by;

Ignition coil shorted to ground and arcing at spark plug wires or plugs.

"SERVICE ENGINE SOON " light wire to EC M shorted to ground. (CKT 419).

Diagnostic "Test" Terminal wire to ECM, shorted to ground.(CKT 451)

ECM power grounds. See ECM wiring diagrams.

Loss of trouble code memory. To check, disconnect TPS and idle engine until "SERVICE ENGINE SOON" light comes on. Code 22 should be stored, and kept in memory when ignition is turned off. If not, the ECM is faulty.

Check for an electrical system interference caused by a defective relay, ECM driven solenoid, or switch. They can cause a sharp electrical surge. Normally, the problem will occur when the faulty component is operated.

Check for improper installation of electrical options, such as lights, 2-way radios, etc. EST wires should be kept away from spark plug wires, distributor wires, distributor housing, coil, and generator. Wire from circuit 453 to distributor should be a good ground.

Check for open diode across A/C compressor clutch, and for other open diodes (see wiring diagrams).

HARD START

Definition: Engine cranks OK, but does not start for a long time. Does eventually run, or may start but immediately dies.

Perform careful check as described at start of Section B.

Make sure driver is using correct starting procedure.

CHECK:

----- TPS for sticking or binding or a high TPS voltage with the throttle closed (should read less than .700 volts).

High resistance in coolant sensor circuit or sensor itself. See CODE 15 CHART OR with a "SCAN" tool compare coolant temperature with ambient temperature on a cold engine.

Fuel pressure CHART A-7.

Water contaminated fuel.

EGR operation. Be sure valve seats properly and is not staying open. See

CHART C-7.

Ignition system - Check distributor for:

Proper Output with ST-125. Worn shaft. Bare and shorted wires.

Pickup coil resistance and connections. Loose igniflon coil ground. Moisture in distributor cap.

If problem exists in cold weather, check cold start valve. See CHART A-9.

A faulty in-tank fuel pump check valve will allow the fuel in the lines to drain back to the tank after the engine is stopped. To check for this condition:

Perform Fuel System Diagnosis,

CHART A-7.

Remove spark plugs. Check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits. Repair or replace as necessary.

If engine starts but then immediately stalls open distributor by-pass line. If engine then starts and runs OK, replace pickup coil.

If engine starts and stalls disconnect MAF sensor. If engine then runs and sensor connections are OK, replace the sensor.

HESITATION, SAG, STUMBLE

Definition: Momentary lack of response as the accelerator is pushed down. Can occur at all car speeds. Usually most severe when first trying to make the car move, as from a stop sign. May cause the engine to stall if severe enough.

Perform careful visual check as described at start of Section B.

CHECK:

- Fuel pressure. See CHART A-7. Also Check for water contaminated fuel.

- Air leaks at air duct between MAF Sensor and throttle body.

- Spark plugs for being fouled or faulty wiring.

- PROM number. Also check Service Bulletins for latest PROM.

- TPS for binding or sticking. Voltage should increase at a steady rate as throttle is moved toward W.O.T.

- Ignition timing. See Emission Control Information label.

- Generator output voltage. Repair if less than 9 or more than 16 volts.

- HEI ground, circuit 453.

- Canister purge system for proper operation. See CHART C-3.

- EGR-SeeCHARTC-7.

Perform injector balance test CHART C-2A.

SURGES AND/OR CHUGGLE --------------------- Definifion: Engine power variation under steady throttle or cruise. Feels like the car speeds up and slows down with no change in the accelerator pedal.

Be sure driver understands Transmission Converter Clutch and A/C compressor operation in Owner's Manual.

Perform careful visual inspection as described at start of Section B.

CHECK:

- Loose or leaking air duct between MAF sensor and throttle body.

- Generator output voltage. Repair if less than 9 or more than 16 volts.

- If a "SCAN" toot is available which plugs in to the ALCL connector, make sure reading of VSS matches vehicle speedometer. See Introduction explaining "SCAN" tool positions.

- EGR - There should be no EGR at idle. See CHART C-7.

- EGR filter for being plugged .

- Vacuum lines for kinks or leaks.

- Ignition timing. See Emission Control Information label.

- In-line fuel filter. Replace if dirty or plugged.

- Fuel pressure while condition exists. See

CHART A-7

Inspect Oxygen sensor for silicon contamination from fuel, or use of improper RTV sealant. The sensor may have a white, powdery coating and result in a high but false signal voltage (rich exhaust indication). The ECM will then reduce the amount of fuel delivered to the engine, causing a severe driveability problem.

Remove spark plugs. Check for cracks, wear, improper gap, burned electrodes, or heavy deposits. Also check condition of distributor cap, rotor, and spark plug wires.

LACK OF POWER, SLUGGISH, OR SPONGY

Definition: Engine delivers less than expected power. Little or no increase in speed when accelerator pedal is pushed down part way.

Perform careful visual check as described at start of Section B.

Compare customer's car to similar unit. Make sure the customer's car has an actual problem.

Remove air cleaner and check air filter for dirt, or for being plugged. Replace as necessary.

CHECK:

. For loose or leaking air duct between MAF Sensor and throttle body.

. Ignition timing. See Emission Control Information label.

. Restricted fuel filter, contaminated fuel or improper fuel pressure. See CHART A-7.

EGR operation for being open or partly open all the time - CHART C-7.

Exhaust system for possible restriction:

- Inspect exhaust system for damaged or collapsed pipes.

- Inspect muffler for heat distress or possible internal failure.

Generator output voltage. Repair if less than 9 or more than 16 volts.

Engine valve timing and compression.

Engine for proper or worn camshaft. See Section 6A.

Secondary voltage using a shop ocilliscope or a spark tester J-26792 (ST-125) or equivalent.

DETONATION/SPARK KNOCK ---------------------- Definition: A mild to severe ping, usually worse under acceleration. The engine makes sharp metallic knocks that change with throttle opening. Sounds like popcorn popping.

Check for obvious overheating problems:

-Low coolant. -Loose water pump belt. -Restricted air flow to radiator, or restrieted water flow thru radiator. -Inoperative electric cooling fan circuit.

See CHART C-12.

CHECK:

-Ignition timing. See Vehicle Emission Control Information label. -EGR system for not opening - CHART C-7. -Fuel system pressure. See CHART A-7. -PROM - Be sure it's the correct one. (See Service Bulletins) -Valve Oil seals for leaking.

Check for incorrect basic engine parts such as cam, heads, pistons, etc.

Check for poor fuel quality.

Remove carbon with top engine cleaner.

Follow instructions on can.

CUTS OUT, MISSES

Definition: Steady pulsation or jerking that follows engine speed, usually more pronounced as engine load increases. The exhaust has a steady spitting sound at idle or low speed.

Perform careful visual check as described at start of Section B.

Check for missing cylinder by:

1. Disconnect IAC motor. Start engine. Remove one spark plug wire at a time using insulated pliers.

2. If there is an RPM drop on all cylinders (equal to within 50 RPM), go to ROUGH, UNSTABLE, OR INCORRECT IDLE, STALLING symptom. Reconnect IAC motor.

3. If there is no RPM drop on one or more cylinders, or excessive variation in drop, check for spark on the suspected cylinder(s) with J 26792 (ST- 125) Spark Gap Tool or equivalent. If no spark, see Section 6D for Intermittent Operation or Miss. If there is spark, remove spark plug(s) in these cylinders and check for:

- Cracks - Wear - Improper Gap - Burned Electrodes - Heavy Deposits

Perform compression check on questionable cylinder(s) found above. If compression is low, repair as necessary. See Section 6.

Disconnect all injector harness connectors. Connect J-34730-2 Injector Test Light or equivalent 6 volt test light between the harness terms, of each injector connector and note light while cranking. If test light fails to blink at any connector, it is a faulty injector drive circuit harness, connector, or terminal.

Perform the Injector Balance Test. See

CHART C-2A.

CHECK:

- Spark plug wires by connecting ohmmeter to ends of each wire in question. If meter reads over 30,000 ohms, replace wire(s).

- Visually inspect distributor cap and rotor for moisture, dust, cracks, burns, etc. Spray cap and plug wires with fine water mist to check for shorts.

- Fuel System - Plugged fuel filter, water, low pressure. See CHART A-7.

- Valve timing.

- Secondary voltage using a shop ocilliscope or a spark tester J-26792 (ST-125) or equivalent.

Remove rocker covers. Check for bent pushrods, worn rocker arms, broken valve springs, worn camshaft lobes. Repair as necessary. See Section 6A.

BACKFIRE

Definition: Fuel ignites in intake manifold, or in exhaust system, making a loud popping noise.

CHECK:

- Loose wiring connector or air duct at MAF Sensor. - Compression - Look for sticking or leaking valves. - EGR operation for being open all the time.See CHART C-7. - EGR gasket for faulty or toose fit. - Valve timing. - Output voltage of ignition coil using a shop ocilliscope or spark tester J-26792 (ST-125) or equivalent. - Fuel System Chart A-7 - Injector balance Chart C-2A - Spark plugs for crossfire also inspect (distributor cap, spark plug wires, and proper routing of plug wires). - Ignition system for intermittent condition. (See Section 6D). - Engine timing - see Emission Control Information label.

POOR FUEL ECONOMY

Definition: Fuel economy, as measured by an actual road test, is noticeably lower than expected. Also, economy is noticeably lower than it was on this car at one time, as previously shown by an actual road test.

Perform careful visual check as described at start of Section B.

CHECK:

Coolant level.

- Engine thermostat for faulty part (always open) or for wrong heat range. See Section 6B.

- Ignition timing. See Emission Control Information label. - TCC for proper operation. See CHART C-8. - Induction system and crankcase for air leaks.

DIESELING, RUN-ON

Definition: Engine continues to run after key is turned off, but runs very roughly. If engine runs smoothty, check ignition switch and adjustment.

Check injectors for leaking. See CHART A-7.

ROUGH, UNSTABLE, OR INCORRECT IDLE, STALLING

Definition: The engine runs unevenly at idle. If bad enough, the car may shake.

Also, the idle may vary in RPM (called "hunting"). Either condition may be bad enough to cause stalling. Engine idles at incorrect speed.

Perform careful visual check as described at start of Section B.

CHECK:

- Throttle linkage for sticking or binding. - Ignition timing. See Emission Control Information label. - IAC system. See CHART C-2C. - Generator output voltage. Repair if less than 9 or more than 16 volts. - P/N switch circuit. See CHART C-IA, or use "SCAN" Tool. - Injector balance. See CHART C-2A. - PCV valve for proper operation by placing finger over inlet hole in valve end several times. Valve should snap back. If not, replace valve. - Evaporative Emission Control System. CHART C-3. - Power Steering Pressure switch input. See CHARTC-1E or use "SCAN" tool. - EGR valve: There should be no EGR at idle.

Run a cylinder compression check. See Section 6.

Inspect Oxygen sensor for silicon contamination from fuel, or use of improper RTV sealant. The sensor will have a white, powdery coating, and will result in a high but false signal voltage (rich exhaust indication). The ECM will then reduce the amount of fuel delivered to the engine, causing a severe driveability problem. Check for fuel in pressure regulator hose.If present replace regulator assembly.

Check ignition system; wires, plugs, rotor, etc.

Disconnect MAF sensor and if condition is corrected replace sensor. "SCAN" tool should read about 6-8 grams per second at idle.

EXCESSIVE EXHAUST EMISSIONS (ODORS)

If test shows higher than normal CO and HC, (also has excessive odors):

Check items which cause car to run RICH.

Make sure engine is at normal operating temperature.

CHECK:

- Fuel pressure. See CHART A-7. - Incorrect timing. See Vehicle Emission Control Information Label. - Canister for fuelloading. See CHART C-3. - Injector balance. See CHART C-2A. - PCV valve for being plugged, stuck, or blocked PCV hose. - Spark plugs, plug wires, and distributor cap. See Section 6D. - Check for lead contamination of catalytic converter (look for removal of fuel filler neck restrictor).

IF TEST SHOWS EXCESSIVE NOx:

Check items which cause car to run LEAN, or to run too hot.

- EGR valve for not opening. See CHART C-7. - Vacuum leaks. - Coolant system and coolant fan for proper operation. See CHART C-12 . - Remove carbon with top engine cleaner. Follow instructions on can. - Check ignition timing for excessive base advance. See Emission Control Information label.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.