88 300CE Emissions testing questions
 

My car keeps just failing government testing. I've checked and adjusted the duty cycle to 47-53 % , but when I check KOEO I see it flash to 70% and then settle to 64%. The readings I've got in the last 2 Aircare tests were as follows
Driving Test
HC Limit 95 ppm (1) 72 (2) 49
CO Limit 0.71% (1) 0.15 (2) 0.12
NOx Limit 1052 ppm (1) 322 (2) 96
Idle Test
HC Limit 108 ppm (1) 161 (2) 137
CO Limit 0.82% (1) 0.02 (2) 0.00
Drivability is good, it starts and idles fine. The last time I had problems like this it was traced to a shorting O2 sensor. The only difference between the 2 tests was an Italian tuneup :D .

Any ideas anyone? Can I tweak the duty cycle to lower the HC at idle, even just for the test, or do I need to have it adjusted with a gas analyzer ?

This part:
"My first ASM test, 1/99, yielded 121 ppm HC at 15 MPH against
a limit of 141 at 63K miles.

Prior to the 1/01 test I installed a new Bosch cap and rotor
and a new set of H9DC plugs and the performance improved
to 87 ppm against the same standard (68K miles). "
Of this post:
http://www.peachparts.com/shopforum/368944-post1.html
caught my eye. Also an oil change and some techron in your 'Italian tune up' couldn't hurt. You're not that far from a pass.

Update
 

Thanks Marty, I've been playing with this since last October. I don't keep plates on it so I've only driven it a few weekends since then. I replaced plugs, cap and rotor about 18k miles ago.I always run Chevron premium fuel, make sure it's hot at the test center. I think adjusting it with a gas analyzer just to lower the HC's is the only way it'll pass.
Last weekend I drove it and had the ABS and CE light come on about an hour after a trip through the touchless carwash. It wouldn't restart (thankfully it happened in my driveway)so I checked the battery voltage and it was only 11.5 V. I charged up the battery and dried out the OVP relay. The next day all was well. I tested the engine and found the following:
KOEO Duty cycle 68% then drops to 64%
Idle contact 9%
Full load contact 19%
Engine running cold 48%
Engine running warm 51-56%
O2 sensor cold and warm 0.1-0.8 V
These are all normal except the KOEO. I drove it about 150 miles on Sunday and as I was going to top up the tank before putting it away the ABS , CE lights came on again so I drove it home and parked it. The battery was at 11.5V again. I recharged it , resoldered the OVP (again)after I discovered moisture inside it.I also tested the OVP and it checked out fine. The low voltage might not be related to the OVP. This is fun :D

It sure would be nice to swap out your computer and see if the KOEO reading goes back to normal. I don't know which part # your looking for but mabey a local indy or junk yard has one you could borrow for the test.


M103 MY 88/89 (Sorry it won't upload any bigger)

According to your specs you are very close. If it were my car I'd tweak CO up a bit, because there is plenty of room, and it might bring HC down. That would be clockwise on the 3mm screw.

Thanks guys for the suggestions and links. Autozen how far on the duty cycle should I go ? 10% or more to make a difference?

HC is unburned fuel from incomplete compbustion. I suggest pulling the injectors out and soaking them for a couple of days in Techron or BG-44 and putting them back in with new seals.

I guess you could do it that way. I would set it according to the readings on my 4 gas analyzer. I think if you bring CO up a bit HC may come down a bit.