I have a 1987 300E its just failed California Smog Emissions test
HC failed at 15 mph and 25 mph , NO failed at 15 mpg and passed at 25 mph. This vehicle does not have an EGR system.
Before I took the test I changed the plus, cap, rotor, and wires. I also changed the two idle air valve hoses and some of the vacuum hose fittings.
This time I put Bosch Platinum plugs in it. Do you think this could be the cause of the high HC? The test two years ago HC was fine.
I performed the check that this thread is based on.
I used a fluke digital volt meter and got the following results:
my vp6 was 13.5V
and my vp3 varied from first 3.8V - 4.4V then from 4V - 4.5V
I used a fluke digital voltmeter
this would give a range of of 67% to 72%
this is not right, I then tried with a Sears Craftsman analog / Volt / Dwell meter from the 80s and got the following.
according to the 6cyl scale the dwell read 33-35 degrees. Not sure if this is the same as duty cycle, but I think it is.
at idle there was very little fluctuation. as I brought the rpm up if move a bit more but not much.
I guess I should check it in the morning when it is cold.
ok I just went out to the vehicle and did a static dwell measurement of pins 2 & 3. I turned the key to the second position (didn't start the car) and the meter read 25 on the 8 cyl scan and about 34 on the 6 cyl scale.
bear with me here I might seem to be all over the map but am converging.
On https://www.landiss.com/mixture.htm I read:
With the ignition on but the engine not running, the duty cycle tells which version of controller is installed. A 70% duty cycle indicates the standard controller with the ability to read some faults by monitoring the duty cycle. 85% indicates the California controller, which ordinarily displays the faults as a blinking LED on connector X92, although it can be programmed to display the faults as an X11-pin3 duty cycle. 100% indicates the controller does not display fault codes in this manner, or is faulty.
interesting that if you multiply my above values by 2 you get : 25 (8 cyl) x 2 - 50 and 34 (6cyl ) x2 = 68 (close to 70)?
is my meter off by a factor of 2? the meter was designed to measure the dwell of ignition points. I used it on my VW rabbits from the 70s to set the point I recall using the 8 cyl scale and then doubling it.
here is a link to the manual of my sears meter
I feel like I am getting close but need some clarity and direction.