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 MANUALSCHEVROLET1986CHEVETTE L4-98 1.6LREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTEMISSION CONTROL SYSTEMSEXHAUST GAS RECIRCULATIONTESTING AND INSPECTIONGASOLINE ENGINES
1986 Chevrolet Chevette L4-98 1.6L
Gasoline Engines
1986 Chevrolet Chevette L4-98 1.6LSECTION Gasoline Engines
Ported Vacuum & Negative Back Pressure EGR Valves
1. Check vacuum hoses for correct routing and EGR valve signal tube orifice for obstructions.
2. Connect vacuum gauge between EGR valve and carburetor and check that at least 5 inches Hg vacuum is available with engine running at normal operating temperature.
3. Depress valve diaphragm, then position finger over source tube. Release diaphragm.
4. Valve is good if diaphragm takes at least 20 seconds to move to closed position. If diaphragm closes in less than 20 seconds, replace EGR valve.
Positive Back Pressure EGR Valve
1. Check vacuum hoses for correct routing and EGR valve signal tube orifice for obstructions. On engines equipped with EGR thermal vacuum switch or solenoid, there should be no EGR valve movement below the calibration temperature. If movement occurs, check TVS or solenoid for proper operation.
2. Remove EGR valve from vehicle, then apply a constant 10 inches Hg vacuum to EGR valve signal tube and observe position of valve. Valve should be closed. If not, replace EGR valve.
3. With vacuum supply still applied, direct a low pressure stream of air into EGR valve exhaust inlet. Valve should open. If not, replace EGR valve.
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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.