A faulty EGR valve can cause a 98 Chevy to fail a smog test. The oxygen sensors should also be tested as they can also cause a 98 Chevy to fail a smog test.
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Late 98 they stopped using EGR valves on the S-10. They installed a block off plate in its place.
A 1998 Dodge Ram does not have EGR.
That's your EGR valve flow is insufficient. Replace the EGR valve.
take the EGR valve off and spray carb cleaner in the egr valve and in the port. This will some times work as it gets plugged up
After removing an EGR valve from the vehicle, the valve can be flushed with carburetor cleaner. If the valve still sticks then a replacement will be needed.
Code P1491 Means: EGR Valve Lift Insufficient Detected EGR Valve needs to be replaced
It's bolted right on top of the egr valve which is on the back of the engine under the throttle body there will be a small vacuum line going into where the egr valve bolts into the intake
screwdriver?
I know on my '98 Prizm it is accessible from the inside down low on the passenger side. Not an overwhelming job.
Its under the EGR on the block ya. follow a hose from egr to vsv from underside of car