I took my 85 to a local STAR certified station and asked if they could do a quick sniff test for me before the official test. The test is simple. One test at idle and one at 2500 RPM. Mine failed HC at idle. The allowable is 120 PPM and mine was registering over 200. My AFR gauge is displaying mid 13's at idle but BLMs are near 128. I've tried tuning the idle but no matter what I do AFRs end up in the mid 13's.

I have to say the technicians were great. They did the free check and offered suggestions on how to get better results. My build is a 396 Super Ram with 221/230 cam. One of the techs commented on hearing some cam but the lead guy quickly chimed in and said he did not have x-ray vision. I have a single Random Technology cat. The test was done with the headers on. They won't be there for the official test. By the way, this engine did pass two years ago but the technician had to work at it.

I'm considering using a Magnaflow front Y pipe with cats from an 86 configuration. My Random Tech cat is a few years old and may not be functioning as well as it needs to.

Any ideas?

 

I am impressed with the tech being reasonable.
Other than the usual change the oil etc.-I just went thru some problems with O2 sensors. I am using heated however same may apply. I was using a bosch O2 sensor and my afr at idle was running low 13s. (wide band) Switched to ac delco and it was back to near 14.1 (10% fuel stioch) BLMs 128 on both. It seems they are just calibrated different-go figure. I'm not the only one that has switched from bosch to ac delco to resolve problems. Of course make sure the O2 sensor is switching rapidly also.

 

I installed new plugs, wires and changed the oil, so there's not much maintenance I can do. I have a fairly new heated O2. I suspect it's a Bosch. It came as a kit. And I also run E10 gas. Do you have a part number for the AC Delco sensor?

 

By the way, what cam are you using?

 

I agree with the O2 sensor... Bosch suck... ACDelco, NGK or Denso.

I also suspect the Random Tech cat... I would consider the Magnaflow CARB legal part.

If nothing else, find a can of "smog chek" and add that to the tank.

 

I called the company that sold me the heated O2 kit. They "think" it used a Denso sensor.

 

Get the car HOT when going back for final check! I mean run it at higher RPM right before the check. They run a little cleaner when hot.

Can't believe they are still doing sniffer tests on 1985 model automobiles in California!��
WOW.....performance car hobby is under attack out there!

 

4) High hydrocarbon (HC) readings usually indicate excessive unburned fuel caused by a lack of ignition or by incomplete combustion. Concentrations are measured in parts per million (PPM). Common causes include a faulty ignition system, vacuum leaks, and fuel mixture problems. Circumstances that can lead to a high HC emissions are:
* Incomplete combustion due to fouled spark plugs.
* Improper timing or dwell
* Damaged ignition wires
* Poor compression
* Vacuum leak
* Ineffective or faulty air management system (ECM control of air/fuel ratios)

 

Try Bringing your base timing back a few degree's and go for a second courtesy inspection..

look at the provided list:

http://www.smogtips.com/failed-high-hydrocarbons-HC.cfm

 

AC-Delco # AFS-74 is a three-wire heated sensor. The GM long# is 25312179.
Or high HC from just running rich.
If you change from the bosch to ac delco you'll also have to change the harness connector.
Added my sig with combo, cam is mild for a 383-222/228 at .050 on 114 lsa. Also with 1.6 roller rockers.

 

If you can pass with a 222/228 114 LSA, then it leads me to believe my 221/230 114 LSA is not the problem. That's a good data point.

I'm confident there's no vacuum leaks. I just had the intake off last week and I was very attentive to vacuum lines and especially the Super Ram gaskets. I installed new plugs and new wires and checked timing. So I'm confident ignition is good, but I can experiment with the timing table to see if that helps. The engine is making great power, so low compression seems unlikely.

There's no doubt this beast is running rich. I just need to figure out why. It's interesting that as soon as I drop it in gear the little load from the converter raises AFR from 13 to mid 13's and the idle smooths out.

 

If its been running rich at idle a lot, I wouldnt be surprised if the RT is gummed up on the inlet side.

 

What's that...

 

Thanks for asking. I'm scratching my head.

And thanks for the smog tips.

 

The Random Tech, mine would get clogged up with soot and blocked up passageways on probably 20-30% of the inlet side of the honeycomb, and the only issue I had was richness at idle in the tune.

 

Ahhh. Is there a way to clean it or do I just replace it?

 

I don't know how to clean a cat out properly if there is a way, so when I saw it I replaced it with true duals and no cats. Which is not an option for you unfortunately.

 

From what others have said, the Random cat doesn't last very long. I think I'll be ordering a CA compliant cat.

 

Does your wideband reading start to lean if you force blm's up? I think the Cat, or better Cats will help quite a bit. Why the narrowband is adjusting to 14.7, but the wideband is seeing 13 is a mystery. Seems like cleaning with cats might go along way.

 

I've tried tuning to lean the BLMs and enrich them. Either way the AFR stays the same. The AFR does track pretty closely to the target AFR in open loop.