I've got the 88 IROC 305 engine
Passes everything except for the CO levels.

Prior the 2nd test I had Timing set to 10 idle. Replaced Cap and Rotor, new spark plugs, new O2 sensor, new radiator with hoses. PCV valve and oil change.

Prior to the 3rd, Dumped marvel mystery oil in the crankshaft and used Chevron Techron additive in the tank, also used the CRC guaranteed to pass stuff too.
What else can I try?

Here are the Readings:

1st test: HC 1.1780 (Pass), CO 24.7233 (Fail) 20.00 is the limit, CO2 428.2630 (Pass), NOX 0.0019 (Pass)

2nd test: HC 1.2023 (Pass), CO 29.3662 (Fail) 20.00 is the limit, CO2 464.4730 (Pass), NOX 1.4529 (Pass)

3rd test: HC 1.2550 (Pass), CO 29.6385 (Fail) 20.00 is the limit, CO2 439.7355 (Pass), NOX 1.2756 (Pass)


I just need the CO to get under 20.00, any ideas?

 

Install a new cat
your timing should be at 6 also not 10

 

Glad we don't have emissions testing in my county...

 

Geez, you had the best numbers before you worked on it.
If you have an actual problem causing the high CO numbers, you have to correct that.
Otherwise, you can pour a quart or 2 of denatured alcohol in the tank. The CO numbers should go to zero.

 

HC is partially burnt fuel - usually bad spark. CO, is from running rich, could be bad regulator making bad fuel pressure, could be leaking injector. NOX went up from advancing the timing - put the timing back and figure out why you're running rich. Check fuel pressure.. Possibly run some injector cleaner - you can use a mechanics stethoscope to listen to each injector to make sure they're all clicking as they should.

 

Can you please elaborate on why the timing should be at 6, what would setting it to 6 do? Also does it account for the higher elevation I live in (6000 ft above sea level)? Thanks again for your help.

 

It will lower your NOX and set at 6 is the factory setting.

 

If you had changed out hard parts in the engine such as heads, that were a slower burning head, increasing the timing may be warranted. Otherwise you may actually be hurting performance. it also tends to increase cylinder temps which increases NOX - you can see that evidenced by your increase in test 2. That also did nothing for you CO and worsened your HC. Arbitrarily changing the timing w/o being able to quantify the results is wasted time.

CO is purely a function of a/f ratio. Now w/ you being at 6000 ft, your air is thinner at about 3% per 1k feet - so 18% thinner than sea level. The computer was most likely tuned for sea level, so if you are resetting the computer then going into emissions w/o giving the computer time to learn your air conditions it could cause the car to run rich - In your case, even if you subtract 18% from your numbers you're still running rich. You'd want to make sure the car has been drivin long enough that the closed loop operation has set the blms to lean out the mixture appropriately

There are some easy tests you can do here. Put a fuel pressure gauge on the fuel logs and measure the pressure there. The mechanics stethoscope I mentioned could indicate a sticky or stuck injector. It would sound different in the tapping they make. Softer or irratic.

If you've ever had the rotten egg smell from your exhaust then you could very well have a bad cat. There are pressure gauges that will plug into the O2 sensor hole to help diagnose a clogged cat.

If you want the quick fix bandaid, You can go to Home Despot or Lowes and buy a gallon of 'Denatured Alcohol' and put some of that in your tank. Your fuel system isn't designed for that, but it would lean out the mix. You'd want to run the fuel down. Add some - google the ratios. Then fill up immediately afterwards and run that out to clean that stuff out of your system.

Just remember that you're not getting the performance out of your engine, or the fuel mileage if you're running rich, which is wasted fun and money.

 

Cat