Topic: Failed smog High Hydrocarbons

[Erjar281]

1991 toyota pickup 6cyl 3.0 250k miles on it.
bought this truck someone had stolen the catalytic on it so we welding a brand new one on.  replaced the spark plugs on it; as they were corroded, from sitting so long?
anywho took it to DEQ and failed.
HC:1033 CO.3727
2nd idle results
HC:1079  CO 1076

guy said its 4x above acceptable hydrocarbon emissions.  a result of unburnt fuel.  my question to you is what do i need to replace or fix to pass.

[Willard]

There is quite a few things that can cause that. For starters now a days these smog techs wont warm up the trucks...they just slap the probe in the tail pipe and run the test. They need to run it at like 2500RPM for atleat 10-15 min so the cat will light off. So if there not doing that then theres one problem. The 02S can also cause problems. I basically always recommend just changing it every time smog is up especially on the single 02S systems. If you do replace is make sure you get a denso sensor and no after market crap. Another thing make sure you dont have any vaccum leaks just spray some carb cleaner around the plenum and etc and listen for idle fluctuations. Make sure your timing is correct and when you check it jumper the correct spots on the test connector. 10DEG BTDC is where you want it.....or where she runs the best. If the smog tech checks everything like he is supposed to do then it has to be set right. Also if the knock sensor is not reading properly then it will read a bias lean and try to richen it up and retard the timing so really check the timing and check it at 2500RPM as well should be around 30Deg BTDC. Those are a few things to check and then if you have any more problems just lemme know. And the CO is usually unmetered fuel.....HC is incomplete cumbustion....low compression....etc.

[1985CRAWLER]

yep you are running rich,or the cat isnt getting hot enough to burn off anything.

had the same problem with my 22re.

replaced the O2 with a few other things like ecu temp sensor and knock sensor and advanced timing a bit and bam it passed even with the nasty cat on it.

again like willard mentioned timing is very important when it comes to smog. being a little off will make it not pass or pass.