Shop used optional 2500 rpm test. Here are the numbers

HC - 557 / pass 220
CO 1.05 / pass 1.20

NOx no longer tested in NJ.

I hadn't rplaced the plugs in years so after the test, we replaced the plugs and tried again. Unfortunately the same result. The mechanic ohm'd the wires and he said they were ok. The car has passed inspection with the same exact configuration 4 times in the last 8 years.

I know that high HC is unburnt fuel. Do you think I should change the cap/rotor and wires?

Any ideas?

 

Look for vac leaks, especially on driver side PCV hose pipe connection to the intake manifold along valve cover. You might spray around connections with starting fluid, if the idle accelerates, you have a leak somewhere. Clean the MAF Sensor with MAF cleaner spray, replace O2 sensor, replace air filter, check timing. Places to start anyways.

 

I am so glad I moved out of that **** state. Why those idiots need to test a 23 year old classic car is just pure BS.

I have heard when I lived up there when they started that insanity that if you dump a bottle of methanol (dry gas) in tank, it will help it pass emissions. But I cannot say if that will help in your situation. If you do it, make sure your tank is just about empty (maximize concentration), and dump in only one bottle. Then fill it up after you are done to dilute it.

Good luck.

 

I assume you have an 1987; cap and rotor definitely. and be thankful you don't have an LT based engine.

also make sure your engine temperature is up. Higher temperatures reduce hydrocarbons. Make sure the thermostat is operating correctly (time for a new 195 degree t'stat ?). Give the car a good hard run immediately before the retest.

 

I added my sig for info on the card.

 

I failed HC last year, but only at idle. I replaced my valve seals, added a gallon of E85 to a full tank of gas, and retarded the timing 3 degrees. I passed and it was the last time it had to go through, as my car is now 25 years old. I have always taken a shotgun approach to passing emissions, which is to try everything that is known to work.

 

Nothing passes unless fuel delivery is deadon and your CO shows that it isn't - in fact it's rich, so it's failed the HC's while barely passing the CO. Electronic Fuel Injection can correct for worn plugs and wires, so more than likely something is tricking it into delivering more fuel than it needs. That's often an exhuast or vacuum leak, so you might want to look at the check valves in the headers and/or make sure the air is blowing to the CAT and not the Headers (air pump system) as well as examine all of your vacuum lines. It's all a great deal easier with a scanner, so spend some money on that and forget the magic elixirs. Assuming it shows that the O2 signal is lean, you can troubleshoot the causes with the diagnostic tree for a Code 44. And since you numbers show that it's rich, it's a good idea to fix it before it eats up your CAT - there's no magic potion for fixing that.

 

compare your reading to this chart..you didn't give the O2 and C02 reading so hard to say how efficient the burn is...could just be a worn out catalyst.

Click here- great gas analysis website

see "chart one"

 

Hope it goes well! Let us know what happens! I have to go in for an Inspection in March! Im dreading it because I know they will do something to my Vette, its just my luck! Have any trouble getting up the ramps with your front spoiler?

 

With a CO that high, doubt it's ONLY a CAT. Most begin to get a little rank at this level which kinda takes the coolness factor down a notch.

 

Indeed high HC is unburned raw fuel. You're either getting too much fuel, not burning it fully in the combustion process for a number of reasons, have a "lean misfire" due to unmetered air entering the motor throwing off the mixture, or any combination of the 3. When you fix the high HC, that CO reading will also go down.

Had similar numbers at idle with my other car. My max HC limit was 120.
I came in at a whopping 594 HC. Near five times the maximum allowable limit.
CO limit was 1%, came in at 1.5%.
Three things fixed it, it was a combination of problems.

New fuel injectors - Some where spitting solid drops of fuel and others simply leaking, making for an improper combustion in some cylinders and too much fuel in others. To find this out I pulled the injectors and had them tested with a bench fixture.
This alone dropped HC down to 200.

New catalytic converter- 285,000 miles on original one. Way past retirement time but wasn't blocked. Running pig rich for an extended period of time does not do them a whole lot of good either, and they don't have to be blocked to be inefficient.

Fixed vacuum leaks - Pinpointed hidden leaks by spraying carb cleaner with a skinny straw around gaskets, hoses, and seals with engine idling while looking at the O2 sensor voltage on a multi meter, with O2 lead disconnected from car to produce a steady reading for testing. If no meter, you will hear the idle raise if the car is sucking in the carb cleaner past a seal, hose, or gasket on command. When the O2 voltage would spike (indicating temporary rich from the carb cleaner it sucked in) on command and idle would raise at the same time, I knew I found the leak for sure. No more unmetered air entering the motor.

New cat and fixing vacuum leaks dropped HC down the rest of the way to under 30.

We can break this down into categories to check:

Ignition:

Weak spark won't sufficiently burn the fuel in the combustion process. Start by doing an ohm check of your ignition coil, particularly the Secondary winding as this is the business side of the coil. Too low a secondary ohm reading indicates a weak coil. If your coil is not within spec range in both primary and secondary tests, replace it. Obviously you want a good clean set of correct spark plugs all gapped to spec. You said the tech already ohmed the plug wires and where fine. Pop the hood open in the dark and look for any arcing from the plug boots (indicating cracked plug insulator), and cap with engine idling. Did he ohm the coil?

Timing:

Spark at the wrong time. I failed with the vette once because of this. Since you automatically fail if you show up with the timing is off unless you fork over $45 for them to reset it for you, I always double check it myself before going in. But unknown to me the balancer ring had slipped since the last time I set the timing. So I had unknowingly set timing to a now false mark and failed miserably. New balancer, re-timed, retested, and passed like nothing with that being the only change.

Vacuum leaks:

Unmetered air entering the engine can create a "lean misfire" which will cause high HC. Remember, you can have vacuum leaks and you won't always be able to feel or hear them and the car can run fine. This is where the carb cleaner or starting fluid helps tremendously. I take it a step further and look at the O2 sensor voltage output at the same time I'm spray around. You can also use propane gas (without flame obviously), but I like the carb cleaner with skinny straw better since you can get into tight spots.

Fuel:

Quick test is with a pressure Gage tapped into the fuel rail shrader valve. If your fuel pressure holds within spec, injectors aren't leaking in the closed position. Leaking fuel injectors can be isolated by pinching off the rubber fuel lines under the rubber filler neck matt while looking at the reading, starting first with the return line.

A bad spray pattern does not allow for proper fuel atomization needed for a more complete burn. Ohming injectors only tells you part of the story, but can identify a dead injector having a break in the coil. It can't tell you about leaks or bad spray patterns. Only a visual can tell you this. You can suspend the fuel rail with each injector inside a clear jar using some threaded fittings and sections of rubber fuel hose and clamps with plenum removed to keep it connected to the car's fuel lines. Distributor harness must be connected to pulse the injectors when cranking key. You'll also see if any are pissing fuel with key on and under pressure.

O2 Sensor:

You can use the car's built in "field mode" feature to verify closed loop operation easily.
Stick a paper clip into the ALDL A&B terminals just like reading codes, but start the car. When in open loop, the engine light flashes 2 times per second. If and when the car goes into closed loop, the flash slows to 1 time per second.

Better yet, unplug the O2 lead and connect it to the positive lead of a multi meter. The negative lead of the meter goes to an engine ground. You want the low voltage scale. You'll be measuring about 1 volt and less. Start the car. At first when cold there will be no reading. After a few minutes when O2 sensor reaches operating temp (about 600 degrees), you should begin to see a fluctuating reading above and below .45 volts if it's working.

Catalytic converter:

A cat does not necessarily have to be blocked to be bad. But if it is blocked you definitely want to change it. And a very easy and quick way to test your exhaust for a restriction is like this.

Take a vacuum guage and connect it to a source of manifold vacuum (vacuum all the time, not ported). At idle you should see about 17-19 inches for most cars . Now raise the RPM to 2500 and hold it.
If it drops by more than 3 inches of vacuum, there is a restriction in the exhaust. The cat then needs a closer look by doing a pressure test in front and then behind it and compare the readings.

 

use seafoam or top end cleaner and try again. you may pass and by you some time to find the real issue

 

high co is a fuel problem high hc is a mechanical problem causing unburned fuel

 

HC is raw unburned fuel. CO is a byproduct of incomplete combustion.

 

I scanned it yesterday and all of the sensor readings were within normal parameters for this car.
One issue I have had from the start since the motor was built and the custom tune was done is that my BLM's are very high the closer I am to idle RPM. Keep in mind I have passed smog at least four times in the last eight years as the car is now.

My mechanic has asked me to work with him during this process (appt. for Monday) so, given my current unemployed state (and limited funds) I will be spending most of the day at his shop going over everything with him. I'm still leaning towards something in the ignition system. As 86pacer asked, he did not ohm out the coil. My cap, rotor etc.. is at least 7 years old and has over 50k miles on it.

 

How does the car run and idle? How's the gas mileage? Take a look at the arc terminals under the cap, as well as the rotor tip.

 

Idle is a little choppy but no different from when the motor was first put in .It idles like crap at first in the winter cold but once it warms up it settles in with a nice lope. It was a little hard starting before the plugs were changed. Mileage also doesn't look materially different than before.

On the passenger side valve cover the hose that connects back to the throttle body has been removed but it has been that way since the beginning. I wanted to pit a breather on there but I couldn't find one that fit properly. I know this is letting in umetered air but like I said previously, it hasn't posed a problem in the past.

I have considered in the past a CD ignition box but I am concerned about there seemingly high failure rate at the worst possible time. In addition, I have seen in many posts by folks here that say they are overkill on a NA motor. I don't really have the funds for one now anyway.

 

Did you cap the TB side?

A bad idle is common on cars with very high HC.

 

Yes, the TB side has been capped. I'm going outside right now (in the 17 degree temp ) to test and see if my fuel pressure is holding after shutoff. I want to eliminate leaky injectors.

 

Keep us posted. Lost of archived threads are left unanswered by the thread starter after fixing it. This can be frustrating for somebody doing a search about the same problem.