Re: [DML] Failed emissions!!!

[Soma576@xxxx]

In a message dated 10/21/2003 7:33:58 PM Eastern Daylight Time, acprice1@xxxxxxxxxxx writes:

> My car failed emissions for THC and CO. It passed for NOx.  
> 
> My mixture screw was tampered with a few months ago (wish I NEVER did 
> that) so I am pretty sure this is the biggest factor here. 
> 
> What gets me is that I leaned out the mixture a bit (tampered with 
> mixture screw again) had it retested, and the results for THC and CO 
> were WORSE. 
> 
> The results for NOx and CO2 improved however, but these 
> were already 
> passing.
> 
> 
> Any and all input is appreciated! 
> 
> Adam Price

Now that i finally understand the dwell meter use, let me try to help you.

First make sure you have replaced all the disposable ignition parts within a reasonable amount of time (less than 5 years at least) and that the fuel system is up to par as well as the idle system working correctly and you really are at zero vacuum advance at idle AND the idle motor and frequency valve are working correctly.  if this, as well as all vacuum leaks and timing are fixed, you can try resetting the CO.

behind the fuel distributer and down by the diagnostics plug you should find a two-wire harness that can be disconnected.  One wire should be purple, one orange.  you will need an analog dwell meter ($40 at autozone) and hook up the test lead to the orange wire in some way (either by cutting and stripping the wire or hooking it up to the harness if you have the right pieces) and put the battery lead on the side firewall terminal.

When you start the car, let it warm up to full operating temperature (upper coolant hose by A/C is hot).  get a long 3mm allen wrench to turn the CO screw.  turn the throttle and run it at about 2000 rpm for a few seconds, then let it go back down. check for idle speed operation and timing.  adjust timing as necessary.  rev it up again and when you let it back down, observe where the needle is on the meter.  my dwell has a 6 cyl scale and after conversion, i find that the needle should be exactly straight up and down, hovering/cycling between 28 and 32.  if you are higher than this, turn the screw clockwise to richen it up, opposite to make it lean.  turn it only a little and replace the rubber plug on the screw hole.  rev it up for a few seconds, then observe where the needle is after about 10 seconds of idle so the ECU can do its thing.  repeat this until the needle is averaging right over the 30 mark.  as you get closer and closer, turn the screw just a hair each time until you are satisfied with the engine sound and needle swing. it will never sound smooth as butter due to engine design, but you know you got it right if you can rev it up and let it back down and you don't hear any booming in the exhaust.

you may find it helpful to get it really close the first time, then drive the car a few days and try it again.  the plugs and such will get sooted at idle and things seem to be more accurate when the car isn't stuck in the garage running for hours on end!!!!

good luck - it took me 3 years and i'm only now getting my idle straightened out the way it should be.  but it's worth it to know everything is working AOK.

Andy