Hi there. I took my car today and it did fine with the high idle test. It failed HCppm on the regular idle test. Everything else passed. But the 1324 HCppm seems ridiculously high and I need to get to 220 HCppm. (The reading was only 90HC when I got it inspected 2 years ago.)
IDLE
HCppm 1324 (220 STANDARD)
CO .09
CO2 9.8
O2 7.0
HIGH IDLE
HCppm 78
CO .12
CO2 13.4
O2 2.8
Why the difference in reading for HCppm in the two tests and what can I do to fix the problem (for hopefully not too much money). I already read some comments that I should drive around on the highway and come in with my engine ‘hot’. How much would this help? And what does it actually do? Thanks!
The car must be fully warmed up before the test. A freeway run might help. You might start with the thermostat, is the car temp getting all the way up? If this car is carbureted, the choke might not be pulling off completely. If its injected, then you might have a leaking or gummed up injector, a can of “Techron” might help here.
There will be suggestions about changing your plugs, you could do this but fouled plugs usually cause high HC readings all across the spectrum. Same for dirty air filter.
EDIT: an oil change right before going in could help also, if you are about due.
My 93 Caprice was 100x over the limit for HC when I took it in for NJ Inspection last summer. Two years before it passed with flying colors.
A sticking PCV valve causing a noticeable drop in oil level was the only obvious problem. I decided to replace the air filter and do an oil change. I put a bottle of Chevron Techron into the gas tank and added 1/2 pint of Seafoam to the PCV hose with the engine running (see the Seafoam can or the website for directions). Before I took it back for reinspection, the PCV valve and O2 sensor were also replaced ($23 total).
Evidently if an OBD-I car sits too long in the inspection line the Cat will not be hot enough to work properly. I drove about 40 miles the day of the reinspection. This time there was no line and the Caprice passed emissions.
Ed B.
Thank you for the quick replies keith and ed b. I’m looking into it…
There’s not near enough info known about the car for me to even start to make a guess.
(mileage, engine condition as in compression, oil consumption, codes, maintenance, etc)
Throwing a wild guess out there what about the possibility of a vaccum leak? At idle with an overly lean fuel/air mix the ECM may be trying to go full rich to compensate for this.
Off idle of course, any small or comparatively mild vacuum leak would not be near as noticeable.
What would I do? Connect a vacuum gauge to the intake manifold and kill that issue real quick. This is bone simple to do and will reveal in seconds if a vacuum leak exists or not.
Note that a vacuum leak can also be present inside the dash of the car and may vary depending on what position the mode control for the heater/A/C is in.
Is this a RWD or FWD car? Carburetor or F.I.? These were dark years for automotive technology. My guess would be a vacuum leak or an EGR valve that sticks open a little…
Too much fuel at idle is the most likely problem. If you get the top off the carburetor, you can check for a float that is leaking, which will make it sink and overflow the bowl.
You would probably smell fuel if this were happening.
The choke may not be opening all the way. Try a rebuilt carburetor.
No matter how warm the engine, you will not change 1234 PPM into 195.
I think you have a carburetor.
From the numbers you presented your CO2 is down, your O2 is up, and your HC is up. It looks like there is incomplete or no combustion somewhere. I would do a full tune up/diagnosis. This would include a compression test, manifold vacuum test, and leak down test. Change the spark plugs while they are out.
Is there any roughness or miss at idle.
I would question the status of the catalytic converter as it should be conbusting the HC and O2.
To update everyone: It’s RWD and fuel injected, no carburetor. The engine doesn’t burn oil, but it runs very rough at idle. Have been thinking about the spark plugs for that… It’s got 198,000 miles on it. And it does has a sort of gasoline-ey smell on occasion when driving with the windows up and vent/air on. Though I don’t know if that is related or not…
A vacuum leak can cause a rough idle and a leaking fuel pressure regulator diaphragm can do the same thing.
At that mileage I’d run a compression test on it. One cylinder down a bit can also causea problem like this.
Compression reading should be up in the 190 PSI range in a perfect world. At 200k miles you can expect it to be less and hopefully not less than 175. When you start getting into the 160 and under range there’s problems brewing.
Does your Buick look like this one?
If yes, then its Front Wheel Drive, not Rear Wheel Drive.
And it has a V-6 engine, which is helpful for us to know.
Series I 3800, most likely.
BC.
If it looks like this one, then its a Rear Wheel Drive version, and can either be a V-6, or a V-8, but I’m not sure if either was fuel injected in this body style.
BC.
um sorry it IS a FWD. (looks like the bottom picture but tan) it’s a V6 3.8 engine. I am really passing this info on to my brother, I am not the best at cars, I only know some. 
He’s pretty good with them. But I know you all really know what you’re talking about, and I think this all helps me.