Matching You with a Pre-Screened Smog Check Center You will Love
Free Online Smog Check Diagnosis
$500 Free Consumer Repair Assistance
Failed Emissions Test
How to Pass the Test
Who Else Wants To Pass the Smog Check
Which Type Should I Choose?
    Forum > Failed Smog Test > Question

Join the community and post your questions. Ask-A-Tech right now!

Failed Smog Test

1981 Buick Century 3.8L failed smog test for high HC

1981 Buick Century 3.8L failed 2nd test High HC PPM reading. Plus engine diesels when shutting down.

We have changed dist cap, rotor, oil & filter, air filter, added higher octane, plus some liquid heat. Should we change plug wires? Plugs are new. Plugs were chhanged prior to 1st test. 1st test @15mph hc was 106 @ 25mph all passed. made changes above. 2nd test 15mph all passed, 25mph hc was 81. Also engine diesels when turning off. Help? Any suggestions?


We recommend looking into why your Buick Century is dieseling first. Dieseling can be caused due to carbon built-up in the combustion chambers which burn hot after the engine is off, providing ignition for any unspent fuel. Dieseling usually occurs when an engine is running very rich, depositing unburned fuel on piston heads and valves. Or when a carburetor doesn't completely cut off fuel supply once the engine has been turned off. Mike, ASE Advanced Emissions Specialist

posted by SmogTips Support 06-05-2012 10:21 AM

No smog check? No problem. Pay your DMV renewal fees now and avoid penalties!
NeedTags - OL #89953. California authorized online vehicle registration service provider.

Related questions and answers you might find useful:

When is a Vehicle Considered to be New for CA Registration Purposes? by Gregg on 05-22-2019 09:05 AM

Dodge Charger Emissions Drive Cycle by Donald on 05-21-2019 12:22 PM

Is a PCV Catch Can Legal for Use in California? by Chuck on 05-18-2019 11:54 AM

Toyota Tacoma Out of State Needs Smog Check by Patsy on 05-17-2019 01:40 PM

What is the Drive Cycle for a BMW M6? by Rob on 05-16-2019 10:27 PM