*update - added isopropyl alcohol, advanced the dizzy, failed again, hydrocarbons were even higher!!*

Vehicle:

- 90 STD hatch
- Freshly rebuilt d16z6
- Full OBD1 conversion
- Proper engine break in procedure followed and 45 miles on the engine

Last night I drove down to the DEQ and had them run an emissions test on this car so I can get it back on the road legally.

My print out says I passed in the NOx, CO, and CO2 categories, but failed THC (which I assume is hydrocarbons 'HC').

The THC standard is 1.20 and my car tested at 2.02. So I'm really not that far off. From the chart they gave me it looks like my car was only above the limit while idling. Here in Oregon they idle your car, then take it up to 30 mph, then back to idle, then up to 30mph etc. they do this four times. Each time my THC was above the limit while idling and fell below the limit during acceleration and deceleration.

I've been searching all morning and here's what I understand:

THC or 'HC' are hydrocarbons or unburned fuel. So, in order to decrease the HC levels I need to burn the fuel more completely.

Now here's where I have seen some discrepency...

One article I read, I think Spade posted it up, said that if the HC was too high I need to retard the ignition timing. But, a few other articles I read said I need to advance the ignition timing.

Advancing the timing makes more sense to me because I can understand how that would cause a more complete burn of the fuel. But which one is it? I trust Spades thread but retarding the timing doesn't really make sense to me as a solution to this problem.

I also read that I can get some "HEET" or something like that which increases the combustion. Another suggestion I read was to use low octane gas (last night I had 93 octane in there) because high octane gas burns slower and could increase the unburnt portion of the emissions.

So what is it???

Do I advance or retard the ignition to decrease HC levels?


Modified by EJ1 wilcox at 11:12 AM 12/22/2005

 

i had the same problem with my car when i had A B16 motor i faild then went back and passed after i advanced my timing and also i had a vafc vtec controler so i leaned the fuel out a little more at lower rpms, if u can get one it will def. help

 

I talked with a guy I work with who builds engines and he told me advancing the timing a bit should take care of the problem.

I also picked up a bottle of isopropyl alcohol that I'll throw in my gas tank.

I am going to check my EACV valve and my FITV as well. I know for sure my FITV is leaking a bit, which could be part of the problem.

Anyways, I'll take it in next week and see what happens!

 

What were your CO readings? Good or just barely passing?

Engine oil can also cause elevated HC readings. Maybe your piston rings need a little more time to seat-in?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Chiovnidca &raquo;</TD></TR><TR><TD CLASS="quote">What were your CO readings? Good or just barely passing?

Engine oil can also cause elevated HC readings. Maybe your piston rings need a little more time to seat-in? </TD></TR></TABLE>

I can't remember my CO readings but they were well under the limit, I mean, not even close.

I totally understand that my rings could need a little more time to seat properly. I'm going to try one more time next week and if I don't pass I'll get a trip permit so I can drive it for a few weeks to let the engine break in a little more.

 

Well, I put a bottle of isopropyl alcohol in my tank, advanced my dizzy as far as it would go, and drove to the DEQ.

I FAILED again!

My hydrocarbons were even higher than before!

Could I have advanced my dizzy too much? What else could be the problem? Could my cat not be working properly?

What else should I try? I've been to the DEQ 5 times now in the last two weeks. If it's not one thing it's another!

 

Any other suggestions?

I think I'm going to switch the cat out for one that I know is good and give it another try.

I'm just sick of driving all the way out there, it takes me 20-30 minutes each way.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EJ1 wilcox &raquo;</TD></TR><TR><TD CLASS="quote">Any other suggestions?

</TD></TR></TABLE>
Post your numbers.

 

i was told that changing the cam gear settings and putting the stock ecu back in and even the stock intake will help me pass smog. is that true? if so. how much does it cost to have the cam gears adjusted?? should i just pay to have my car passed? or adjust the things i need to in order to pass??

 

It sounds like either your cat is going bad (maybe cooling off at idle) or your fuel mixture is off. You need to post all the readings when asking a question like this (they all relate to each other). For example if your fuel mixture is lean your CO will be low but HC's will be high. You could have a bad O2 sensor which isn't bringing the fuel mixture toward stoich (again, the O2 sensor could be cooling off). With a good cat your ignition timing, if reasonable should not effect it *that* much. Definately don't crank it all the way advanced, that's a little extreme.