dms0309

Hi everyone,
I previously posted that my 85 failed for emissions, the reading for HC at idle was 1476ppm, standard is 220. I received a good reply to check my injectors and CSV. I did and found 2 injectors that were no good. I sent my CSV to FIC for a cleaning and inspection and also ordered a set of Bosch III injectors from FIC. I installed them set up the FP and did a major tune up. The MAF, temp. sensors are all good as is the O2sensor. The only thing I did not change is the Cat because all my other readings like Co Co2 O2 are perfect and the car easily passes all tests at high idle.
Well I went today for re inspection and it again failed for high HC 800ppm at idle and it again passed everything at high idle HC 80ppm. At this point I really don't know what to do, it's not a high mileage car and the difference in performance after the fuel injectors and tune up is incredible.
Does anyone have any suggestions. I'm starting to wonder if an 85 is capable of passing the emissions test. Thank you for any help.

GKK

High HC levels are the result of poor combustion.

The most typical cause is a bad ignition system which could be incorrect timing or defective and worn ignition components.

I would suggest doing a complete tune up including all ignition components, an oil change and new O2 sensor which get weak over time.

dms0309

Oil change done, O2 sensor is new, it has a new cap and rotor also new plugs and wires. Checked the timing 6deg. I have and MSD 6a ignition and Blaster 2 coil that are not new.

GKK

If your engine was operating with high HC levels for a long period of time, the unburnt fuel going through the Catalytic Converter would cause very high temperatures and could've damaged the Substrate.

A new Catalytic Converter might be needed.

dms0309

I considered the catalytic converter but I wondered why my other readings were good and my HC was only 80 at high idle. Also is it possible for a Catalytic Converter to lower my HC from 800ppm to under 220ppm at idle? Thanks for your help.

xrav22

I replaced 3 cats on 3 different 1 cat cars, after a fail and the cat will usually pass once. Just get it hot before you go.
Moisture caused the inside to rust and they just don't work as well.
The smog guy told me to replace them and it should pass he was right.

corvetteronw

I believe the 85 only has one converter. Here is a decent one from Corvette Central. I have had 3 of these over the years on different Vettes and they work fine:
http://www.parts123.com/parts123/yb....5Z50000050F~~~
I hope you don't live in California as the price for the CA model is much higher at $299.

dms0309

I know I'm asking a tough question but just to be sure do you think that the converter can make that much of a difference to get my HC from 800 to under 220ppm.

dms0309

There is something I didn't mention in my posts and I'm not sure if it means anything but it is odd and since checking my ignition system was mentioned it might be worth noting. My engine would always take about 3 seconds to start, after replacing the distributer cap, rotor and plug wires I started it to check everything. The engine started instantly! and ran great, I tried it again and the same thing, I thought that I must have fixed something. I took it out for a test drive and it felt great. Now heres whats odd the next day when I started the engine it was back to taking about 3 seconds to start but when it did there was no notable difference in performance and it still runs great. The only thing on the ignition system that was not changed was the MSD 6A and Blaster Coil, could either of these be a problem, does the coil wear down over time?

GKK

Yes, the ignition coils can go bad and some have had problems with the MSD 6A ignition box.

Also, Check your fuel pressure since long crank times usually point to a failing fuel pump or fuel pump relay.

When the fuel pump relay fails, the Oil pressure switch sends +12v power to the fuel pump after the engine builds enough oil pressure which results in a longer crank time.






.