Failed emissions (High HC reading). Help?
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Joined: Aug 2009
Posts: 58
Likes: 2
From: Denver CO
Failed emissions (High HC reading). Help?
So my '85 'Vette failed emissions today, but barely. It passed everything except the HC gpm (which I am reading now is Grams Per Mile). Limit is 2.5000, my car blew 2.8550... Any ideas on how I can remedy this? I just did a spark plug change on the car a few weeks ago. It does idle very slightly roughly somewhere around 5-600 RPM, I don't know what is normal for these cars, though. It seems to rev ever-so-slightly when idling, but nothing severe.
I don't really have the extra cash to just drop it off at a mechanic and tell him to fix it, so I'd really like to be able to figure this out myself without having to replace everything in the engine to get my car to drop .3 grams of whatever it's measuring...
Thanks!
I don't really have the extra cash to just drop it off at a mechanic and tell him to fix it, so I'd really like to be able to figure this out myself without having to replace everything in the engine to get my car to drop .3 grams of whatever it's measuring...
Thanks!
Burning Brakes
Joined: Aug 2006
Posts: 1,061
Likes: 99
From: Seattle WA
The high HC reading is a result of having too much unburned fuel in your exhaust (incomplete combustion). There could be a number of causes - plugs not firing consistently (did you gap the plugs correctly? how are your cap/rotor/wires? etc.), too rich a mixture (faulty o2 sensor, temp sensors, etc.), lean miss (vacuum leaks, clogged fuel filter or injectors), burning oil, failing cat, etc. etc. Any trouble codes/check-engine light lit?
Was the car thoroughly warmed up for the test? The engine oil should be up to temp (180+) and the catalytic conv needs to be hot to work well. If you weren't warmed up, you should pass on a retest if you drive 15 min or so ahead of time.
However, the rough idle and hunting indicate you still have an underlying spark or mixture problem that's tough to diagnose over the web.
Was the car thoroughly warmed up for the test? The engine oil should be up to temp (180+) and the catalytic conv needs to be hot to work well. If you weren't warmed up, you should pass on a retest if you drive 15 min or so ahead of time.
However, the rough idle and hunting indicate you still have an underlying spark or mixture problem that's tough to diagnose over the web.
Melting Slicks
Joined: Aug 2008
Posts: 2,082
Likes: 50
From: Palmdale CA
89onlyZ51 is right on the money...but your close, I would do a few simple things and re-try.
New PCV...helps to reduce crank case gas's.
New air filter...max air flow.
oil change...no contaminents.
High octane fuel...I've had the best luck with high test fuel.
Drive it at freeway speed for awhile, and re-test.
New PCV...helps to reduce crank case gas's.
New air filter...max air flow.
oil change...no contaminents.
High octane fuel...I've had the best luck with high test fuel.
Drive it at freeway speed for awhile, and re-test.
Melting Slicks
Joined: Jan 2009
Posts: 3,482
Likes: 196
From: folsom california
Ask your smog man to flow some propane from a small hand held bottle into your engine; its counterintuitive, but a too lean condition (usually due to a vacumn leak) cause incomplete combustio resulting in a high HC reading. If the propane causes the HC's to go down your engine is too lean. If the HC's go up your engines too rich.
Let's assume your engine is, in fact running slightly rich. Do a basic tune up, rotor, rotor cap and especially plug wires; some plug wires only last a year or two at best even though they look fine from the outside; if you want you can check their total resistance with an ohm meter. Purchase some "mechanic in a can" i.e. a gas additive "guaranteed to pass smog" which is nothing more than an oxygen rich additive. Make sure the engine is fully warmed up, even if it means replacing your thermostat with a high temp (195 degree) stat; all research indicates that HC's go down significantly with increased temperature. One final thing to check, make sure your charcoal cannister is working properly and most importantly, that it hasn't become fuel soaked.
Good luck. You should pass.
Let's assume your engine is, in fact running slightly rich. Do a basic tune up, rotor, rotor cap and especially plug wires; some plug wires only last a year or two at best even though they look fine from the outside; if you want you can check their total resistance with an ohm meter. Purchase some "mechanic in a can" i.e. a gas additive "guaranteed to pass smog" which is nothing more than an oxygen rich additive. Make sure the engine is fully warmed up, even if it means replacing your thermostat with a high temp (195 degree) stat; all research indicates that HC's go down significantly with increased temperature. One final thing to check, make sure your charcoal cannister is working properly and most importantly, that it hasn't become fuel soaked.
Good luck. You should pass.
Pro
Joined: Apr 2008
Posts: 502
Likes: 37
From: Pine Barrens New Jersey
I don't know if its possible, but a reduction in base ignition timing for the test will also clean up the hydrocarbons. The car will run crappy but pass. Then put it back when you get home.
Drifting
Joined: May 2006
Posts: 1,428
Likes: 7
From: Chewelah Wa
Did it fail at cruise or idle? I failed miserably at idle this summer and did all of what was suggested above, but I think the big thing was that my car was smoking excessively at idle due to the fact that I had defective valve seals. I replaced them and passed. I also put a gallon of E85 in with a full tank of gas. This was the last year I had to go though emissions, yay!
Melting Slicks
Joined: Nov 2000
Posts: 2,469
Likes: 6
From: Winchester Ontario
My 383 superrammed stroker with a choppy cam (230/230 0.598" 110 LSA) passed e-test. Initially it failed because of HC readings at idle.
Here's what I did and it passed with flying colors. First, I disconnected the ESC wire by the distributor so it only ran off base timing without computer (6 degrees). This threw a Service Engine Soon light once I tried to start the car, and had to help it idle for the first 5 - 10 seconds, then it idled fine.
I then raised the idle portion of the test to 1400 RPM instead of 850 RPM. I am not sure how they do e-tests by you, so I don't know if they'll allow that. But, by doing these two things, I passed very easily and had the operator scratching his head wondering how I could be so clean.
Idle vid.
Here's what I did and it passed with flying colors. First, I disconnected the ESC wire by the distributor so it only ran off base timing without computer (6 degrees). This threw a Service Engine Soon light once I tried to start the car, and had to help it idle for the first 5 - 10 seconds, then it idled fine.
I then raised the idle portion of the test to 1400 RPM instead of 850 RPM. I am not sure how they do e-tests by you, so I don't know if they'll allow that. But, by doing these two things, I passed very easily and had the operator scratching his head wondering how I could be so clean.
Idle vid.
Last edited by black_89_vette; Oct 13, 2009 at 09:21 PM.
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Le Mans Master
Joined: Mar 2004
Posts: 5,107
Likes: 171
From: Dublin CA
Sent you a PM.
Check your fuel pressure regulator. Pull off the hose and see if there is fuel in the hose. If so, you have a broken diaphragm in the FPR that needs to be replaced.
Pull computer codes to see if there are any stored. If you don't know how to do this, send me a PM and I will send you directions.
John
Check your fuel pressure regulator. Pull off the hose and see if there is fuel in the hose. If so, you have a broken diaphragm in the FPR that needs to be replaced.
Pull computer codes to see if there are any stored. If you don't know how to do this, send me a PM and I will send you directions.
John
Safety Car
Joined: May 2002
Posts: 4,010
Likes: 26
From: Somewhere nowhere
my car also just failed with high HC's. it was double the allowed.
BLM's are way high, 145 at idle, but the exhaust definately smells rich.
this is with new ACCEL 21 lb injectors. Some reason new injectors don't work with a stock prom.
BLM's are way high, 145 at idle, but the exhaust definately smells rich.
this is with new ACCEL 21 lb injectors. Some reason new injectors don't work with a stock prom.
Pro
Joined: Jan 2004
Posts: 565
Likes: 0
From: Toronto ON
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
21 lbs injectors work fine with a stock motor. Make sure one of them isn't leaking down - check fuel pressure or pull plugs to see if one is particularly rich. Clamp off the Evaporative Emissions Hose to see if the BLM's swing back to normal.
Pro
Joined: Jan 2004
Posts: 565
Likes: 0
From: Toronto ON
A bad Multitec stock injector had me fail once but HCs were like 10X normal in that case. Some good tests suggested here- you've got to get to the bottom of it.
SunCr- if the stock injectors are indeed 19 psi, would you agree the 10% difference could be the cause?
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
'89 stock is 22. I've been running these same injectors for about 8 years and my BLM's are deadon. My first set did have a leaker which I sent back and another which leaked externally due to a piece of flashing that interfered with the upper O-ring. Others around here, at the time, had similar experiences and ditched them for another brand. Follow the Code 45 Diagnostic Aids in the Shop Manual to find out where the extra fuel is coming from.
