failed emissions, where to start?

[tigmaned]

well i took my 1986 vette to the Maryland emissions testing today and got a bad report.
state standards for Hydrocarbons is 220ppm and my vette blew it with a 579ppm at a idle.. got home and did a scan for stored codes and got nothing.
i guess i'll look for vac leaks first and see what else i find??
CRAP!! got to spend $300 before a wavier.

 

[Z06Marty]

Tested my 90 in January, HC was 29 ppm at idle and 20 ppm at 2500 rpm. The max allowable here in California is 120 ppm for a 90 model year car. Getting the hc reading down to acceptable levels has got to make your car run better and use less gasoline. As a side note, my car came from Florida, does not have California emmisions and has 103,000 miles. Marty

 

[gary55r]

Go to Kragen or Pep Boys and buy some "Guaranteed To Pass" fuel additive $9.95. I used it and just before I finished off the tank I took in in for the test when the engine was nice and hot. I did this to increase my chances of passing the first time.
Worked for me.:cool

Gary

 

[JonM]

Here are some probible causes...

http://www.aircare.ca/index.php?repinfo-ere-causes-hc.php

BTW...was the car warmed up good?

 

[tigmaned]

jonm

thanks for the site, it says high hydrocarbon reading is a lean condition?

 

[JonM]

jonm

thanks for the site, it says high hydrocarbon reading is a lean condition?

Depends...how were the CO readings? If they were also out of wack, it would mean a lean condition...If not its usually a rich condition...does it smoke out the pipe or smell like raw gas?

 

[Vettelt193]

how many miles do you have on it? high HC can also come from burning oil too

 

[tigmaned]

she only has 86K miles. got a brand new exhaust syatem too. CO reading on the paper says 0.00 PCT. and below it pass. HC 579PPM, and below it fail. i checked all the vac lines and they seem o.k. only thing i see is the one wire EGR temp sensor going into the little tube on the pass side with the foil wrap on it. well the wire seems loose and i can spin the connector in side the screw in part. how strong should the vacuum in side the line going to the EGR value be? with the engine running i pulled it off and i almost can't feel any vacuum in the line, is that right?

 

[nyernga]

This may sound crazy but it worked in my case 2 years ago. Make sure they close the clamshell before taking readings. After I failed I brought the car to my mechanic and he immediately drove it back to the inspection station without touching it except he insisted that the clamshell be closed...........I PASSED

Len

 

[tigmaned]

clamshell, you mean the hood? if so it was closed.
any body know if i had a bad EGR tamp sensor would that fail it, and would i get a code if it was bad?

 

[bradfordsvettes]

I would be giving the O2 senser a close look if it is contaminated it would make the computer see lean and fatten fuel mixture up quite a bit my 2 cents Steve

 

[PLRX]

well i took my 1986 vette to the Maryland emissions testing today and got a bad report.
state standards for Hydrocarbons is 220ppm and my vette blew it with a 579ppm at a idle.. got home and did a scan for stored codes and got nothing.
i guess i'll look for vac leaks first and see what else i find??
CRAP!! got to spend $300 before a wavier.

Are you in So. California?

 

[Edmond]

Give her a nice tune up. You'll likely pass and get better gas mileage afterwards.

 

[Mad-Mic]

O2 sensor, clogged cats, tune up, air filter, and a few other tricks i can show you.


PM sent.
BTW went in around the same HC count as you 500+ and after a few things passed with 180 HC ppm

 

[jmccloud]

Fail MD emissions

The EGR shouldn't be active at idle, so it probably isn't the cause of your high HC readings.
A rich condition will cause high HC, usually due to the oxygen sensor being bad or not warm enough. You mentioned that your exhaust system is new. Did that include new oxygen sensors? And are they the correct ones? And are they connected?
It usually requires several miles for the closed loop control system to take over (when the correct temperature is reached). My '95 seems to go 'closed loop' at about 120F as the instantaneous MPG reading takes a jump up at that point. So be sure to drive 15+ miles before the test and don't shut it off until they tell you (they test the gas cap first).
A lean condition can cause high HC if the condition is severe enough to cause misfire. Your cats should burn off the excess but perhaps not enough to pass. Does you new exhaust system include cats?
MD does experience 'false rejects'. I failed due to 'oxides of nitrogen' one year and changed the oxygen sensor out of desperation (not a Corvette). When I returned for the retest, a technician was working on the equipment and fiddled with it a lot during my test. He was talkative and I discovered that they had rejected a lot of cars earlier in the day! I passed.

 

[tigmaned]

JM

the new exhaust was put on before i got it. it dose have a cat. O2 sensors now no idea? but i will change them or it asap, and i will change the EGR temp sensor since it seems like its broken. i am i right my 86 only has one O2 sensor? i think thats all i have seen. i was driving the car all morning and left it running in line for the test, they told me to shut it off when they did the gas cap test. closed loop means when the ECM takes over right, how do you know its in closed loop? i have a code scanner and i am not getting any codes, just the 12, which means the system is working, i think.

 

[Edmond]

Closed loop is achieved when the car reaches a certain temperature. I think it's roughly when the coolant reaches 150 or so but don't quote me on that.

The '86 should only have one O2 sensor. It will be located on the exhaust manifold. I want to say it's on the driver side manifold. I just did mine last fall, but I've forgotten already. It's very easy to do.

The unfortunate thing about OBDI is that it doesn't get very specific unlike OBDII. OBDII will tell you exactly what to look for while OBDI just gives you a general idea. From there, you have to go searching.

 

[tigmaned]

o.k. if closed loop happens at 150 i should be o.k. i am at 180 most of the time and 180 during the test. napa has a bosch O2 sensor for $21 so i'll try it and see. i also have a coolant temp sensor i haven't changed it yet. well found a AC-delco O2 sensor off ebay for $10.

 

[RedRagTop]

Emissions test? What the hell is that?
Kidding, we don't have them here YET but...

 

[tigmaned]

and were is that?? i think almost every where is going to be having them soon?