1987 Toyota Pickup Smog Machine Says Excessive Dilution

I took my 1987 Toyota Pickup truck to get a smog test. Was told the smog check machine wouldn't proceed due to excessive dilution. I replace the exhaust manifold, so there is no longer an exhaust leak, and I replace the plugs, wires, rotor, cap, air cleaner, O2 sensor, oil, filter, and pcv valve. Still the smog machine won't proceed due to excessive dilution.

Do you have an idea of what else I should check? Thanks.

Answer:

Your Toyota Pickup truck can be causing the smog machine to show "dilution" because of high O2 (oxygen). High O2 can be caused by a lean air/fuel mixture. Usually however a smog check machine will show dilution when there is a large leak in the exhaust pipe. This exhaust leak will let air enter the exhaust system and cause the smog machine to not allow a smog inspection.

You can also check your Toyota Pickup trucks air injection system (if equipped). If the air injection pump is pumping air into the exhaust at all times (instead of when the engine is cold and/or when the engine is accelerating) high O2 emission will result. Air Injection is used to aid in the burning of HC.

Follow the link below for more information on Air injection Systems.

http://www.smogtips.com/air.cfm

posted by SmogTips Support