CA Smog fail journey

So my 96 failed smog yesterday. High Hydrocarbons. Took it to a mechanic and he wanted over $1000 to do plugs wires and coils and said even that might not fix it. So I’m going to do all those myself using Denso parts. Anyone have any other suggestions for stuff to do before I take it back for a retest? I’m really hoping it’s not the Catalytic converter. Should I do any sort of injector cleaner or seafoam type flush? It’s got 215k mi and it’s the 3.4l motor.

 

Awww, crap... you wernt flagged as a gross polluter were you? If the CAT was "bad" there would be a code. PM sent.

 

Make sure engine is hot, same for catalytic converter. Advice, don’t turn off the truck and wait for your turn for the smog, that will cool the cat and engine down depending on timeframe.

Changing spark plugs, wires, coils (if applicable) and make sure there’s no vacuum leak, and possibly changing the oxygen sensor.

 

Drive the truck for several hours before doing the smog. You can do i fuel cleaner/seafoam BUT I would wait a few days before taking it back for testing. If money is not an issue for you and you havent changed any of the listed parts you mentioned I would just change them out. Definitely check for vacuum leaks. Good luck

 

Post the numbers, did you have fresh oil?

 

Fresh oil, pull the brake booster hose or introduce a vacuum leak for a minute on a warmed up engine (burns carbon off o2 sensors). You can even run a little bit of rubbing alcohol, depending if its failure readings were. It burn hotter. Seafoam is a great cleaner but IMO should be done only way ahead of time or if you pull the spark plugs after to check/change. It can plug up your spark plug gap with carbon.

 

I went through this CA smog hell about a year ago with my 1996 3.4L. Super frustrating. I spent lotsa $ and the smog shop wasn't particularly helpful (they suggested that my ECU needed to be replaced - it didn't). The actual solution: replacing both O2 sensors with new OEM (Denso) ones, then driving it a bit to reset things. This after a number of people told me that this could not possibly be a solution.

You can follow my epic journey. Best of luck!

 

An exhaust leak is one possibility and easy to test for. Duct tape a shop vac hose to your tailpipe and blow air inside. Engine off of course. Spay all exhaust connections with soapy water between the engine and 1st o2 sensor. A leak will make the o2 sensor read a lean condition and the ecu will dump fuel and you will produce high hydrocarbons. A fresh set of NGK 3967 plugs and Denso wires is always a good thing as well. Make sure your mass air flow sensor is clean and absolutely no intake leaks. Our motors are very sensitive to intake and exhaust leaks.