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1997 Toyota Celica - EGR Trouble Code - EGR Flow Insufficient

My Toyota Celica has failed the smog check 3 times. It shows a P0401 EGR flow insufficient. I have taken the egr valve off and cleaned it and the check engine light goes off but when its smog test time it comes back on. The car has been sitting.
Answer:

The possibilities are either the EGR flow sensor is defective, or the EGR valve itself is clean (since you removed and cleaned it) but the passages within the intake manifold and/or the EGR exhaust tubing is still dirty and restricting EGR flow. Check to make sure all passages are open. A smog check station would test the EGR valve flow by attaching a hand vacuum pump to your Toyota Celica's EGR valve directly, and attempting to open the valve manually. If there is adequate exhaust flow through the EGR valve this procedure should cause your Toyota's engine RPM to drop to at least 500 rpm while the valve is open. If engine RPM drops, but not nearly enough to stall the engine, then you've got a exhaust flow problem and you should re-check the intake and exhaust ports. posted by SmogTips Support

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