View Full Version : Failed emissions....plugs and wires...?

07-09-04, 04:51 PM
Hey guys,

Just bairly failed my emissions test about an hour ago. It is probably time for a tune up again. Getting near that 180K mark as we speak.

I hear most board members suggest OEM stuff in my searches on the related topics but is that still how most of you feel. With the advent of the iridium plug and its relative cost comparison with the GM AC Delco replacement....would I see any benefit to go with those. They are supposed to last about as long.

Also...what wire....AC Delco replacements and if so...where is the cheapest place.

This is one addy I have...any others...?

I have heard of GMParts online...not sure of the website.

Thanks and car is a 1993 Seville STS. :confused:

07-10-04, 01:15 AM
Before you jump to conclusions and start replacing parts willy nilly....what emissions constituents failed...??

If HC or CO failed then some sort of fueling or misfire might be suspected. If NOx failed then the EGR system is somehow deficient most likely.

You have to know what you are trying to fix before you start throwing parts at it.

If the phenolic spacer plates between the intake manifold and the cylinder heads have never been cleaned then I would suggest starting there. The EGR passages in the phenolic spacer plates and the machined notches in the heads at each intake port need to be clean to allow correct EGR flow so as to pass the NOx levels. If the EGR flow is disrupted by plugged passages in the plates then it can also affect the fueling and the HC and CO emissions.

07-12-04, 01:47 AM
Thanks for the heads up. I will check. It is my father's car and I know that the plugs and wires are only the first replacements so they are probably due as well but I will look into the EGR if the data indicates that the NOx was high.

07-12-04, 02:00 PM
Slightly elevated HC levels were the culprit. I tested the ohms per foot on the #4 wire and it was right about 40,000K ohms. I guestimated #4 to be just over 4 feet so the wires I think are right below max resistance. I will run some BG 44K and slap some new plugs in it and see if that is enough to get me by for now. Thanks. If I fail again, I will look into those EGR passages as you recommended but given that NOx levels were relatively low...I think I am okay there.