Emissions Test - FAIL!


Active Member
Apr 8, 2004
Ontario, Canada
Hey guys, just took my car into the shop today to get it e-tested. Its been runnin real good since yesterday when I put new plugs, wires, distributor cap, and rotor on it... so i was hoping it would pass. Naturally, nothing works out properly. It didnt do so terribly tho, it failed one category. High rpms, it failed Hydrocarbons (HC). I was wondering what might be the cause of it? Cuz they want $75 for a diagnosis!!! So what would cause high HC at high rpm?
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Its running alright by the sound of it... when I changed the plugs, it had a bad plug (or wire or something), but now it seems to run better. Its got the smog pump + original h-pipe, everything is factory on it.

1912rpm... HC = 272 (max allowable is 66ppm)
this that would cause high HC is a missfire. It could be leaning out and missing, could be a ignition mis. You sure you didnt crack a plug or anything installing them? Can you tell us the rest of the reading co co2 o2 and nox if it has it.
Sure, I re-created the exact chart... here it is;


I installed the plugs and wires myself, there seems to be no problems, except i did notice a slight 'tick tick tick' noise coming from the engine... not positive on that one.
Step 1.) Dump the codes and see what the computer says is wrong…

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great.

See http://www.troublecodes.net/Ford/
See http://www.mustangworks.com/articles/electronics/eec-iv_codes.html

IF your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

For those who are intimidated by all the wires & connections, see http://www.actron.com/product_detail.php?pid=16153 for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Walmart.

Or for a nicer scanner see http://www.midwayautosupply.com/detailedproductdescription.asp?3829 – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $33.

Step 2.) Post your results & we will try to help you fix them

Step 3.) Fix all the codes, now you can pass the emissions test.
That ticking is prolly from a plug wire that came loose after the install. I just changed my plugs and I heard a ticking sound and i checked and it was the plug not all the way on. Just start from the begining to save some money. :D
okay, pulled codes today... gave me 2 stored codes, no others...
29 - speed sensor failure ??
31 - EGR Valve

retested about 3 times, it kept giving me the same stored codes, no new codes. Checked all plug wires, did all tests KOER, KOEO, and the individual cylinder test... the KOER and cylinder tests gave no codes.
jrichker said:
More than stock spark advance, non-functioning EGR valve, higher than stock compression ratio.

I failed my emissions with almost 3 times the limit here in SoCal. Realized the timing was set at 14*.. Try again, this time bump the timing back down to 10*, getting an h pipe in which the cats are still good, new plugs, new wires, new cap and rotor. Hopefully I'll pass this time.
With a code 31 your almost garunteeing your self a new Egr valve and EVP sensor. I have seen many of these issues and 99% need both valve and sensor. If your sensor was reading biasly low it would give extra egr at cruise and induce a slight miss hence high HC. Also if possible timing should be checked too and set to factory specs. If it was me I would replace both egr valve and EVP sensor because of the high failure rate.