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Hc (ppm)levels to high in 95' Chevrolet Tahoe. How to fix?

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Posted on Jan 02, 2017

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SOURCE: volvo 850 wagon failed NOx emissions test - badly!

Hey Pitloops!
It seems likely that one or both of your o2 sensors are acting up, or that your engine is sucking in unaccounted air from a leaking vacuum tube. Spray the tubes with "start gas" while the engine is idleing. If you hear it revving up when you spray the gas on the tubes you'll know there's a leak.
I'll sacrifice a squirrel for you and hope that the problem isn't your o2 sensors since they can be expensive to replace. is probably the cheapest part supplier online if you'll need new sensors.
You might also want to clean your throttle body, as it usually gunks up with carbon deposits and sludge over the years. It only costs you the price of the carb cleaner to do it and the car will probably run better afterwards even if it doesn't solve the problem.
Good luck!

Posted on Jun 27, 2009

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SOURCE: how to remove the headrest from a 95 chevrolet

When you lift the headrest to the up position on the plastic sleves at the bottom of the metal rods for the headrest you should find a small hole on one side.Take a small pin or nail and push in the hole and lift up that will release the headrest

Posted on Jul 12, 2009

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SOURCE: Toyota Camry - 1998 3.0 L V6 = Failed emissions -

Burning oil...Engine miss. lazy o2 sensor.. dirty maf sensor. check the data on a scanner and this will tell what is amiss.

Posted on Jul 13, 2009

  • 1111 Answers


possible but could be head gasket or valves , or worn rings and is by passing the pistons going straight out the end ...or maby settings are wrong ? try carb cleaner and inspect visually air-filter etc.

Posted on Aug 26, 2009

  • 1 Answer


I have a 94 Tbird with a reading of 790 NO ppm at 1871 RPM, I put about a liter of water into the intake at about 2000 RPM and changed vacum lines to EGR valve,(may have been cracked), now the reading is only 214 NOppm at 1348 RPM. This much change I don't understand. Maybe this info may help someone.

Posted on Sep 17, 2009

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I have 1994 chevy 1500 it failed smog at idle . the hc ppm was100 max and i was putting out 848 what should i do. the high idle test at passed fine max is1.0 and i was.95

May not be much you can do yourself without a scanner and an exhaust gas analyzer.
High HC is too much fuel. So it could be a leaking injector, O2 sensor, air flow problem, or something else.
It could also be not up to normal operating temp due to an open thermostat.
Without the proper equipment you really have no way of knowing whats coming out the tailpipe.

Apr 08, 2016 | Cars & Trucks

1 Answer

Reason for failing emmision hc ppm idle on a 1996 chevy suburban 454 truck


First of all, HC (Hydrocarbon) are the residue of petroleum based product combustion. If your HC reading are higher than the OBD2 legal limit (220 ppm), the most common causes could be a leaking fuel injector, abnormal oil consumption, a faulty Oxygen sensor or worn out spark plug / distributor cap / spark plug wire. To be honest, I would need more accurate details such as NOx ppm, CO ppm, CO2 ppm and Oxygen ppm and if there is any repair that have been made on the car recently to give a proper diagnostic.

Warm regards

Mar 16, 2015 | 1999 Chevrolet Suburban

1 Answer

What dose HC (PPM) stand for how do you get the numble down

HC is hydrocarbons. This is unburnt fuel. PPM is the amount of fuel in the mixture and it is in PARTS PER MILLION.
There are a lot of possible causes:
1. Dirty air filter. Not letting enough air into the engine.
2. The ignition timing is bad. It is too advanced.
3. The ignition system has many parts that could be worn. Plugs etc
4. There is a vacuum leak.
5. The Catalytic converter is worn out.
6. Low compression due to valves or piston rings
7. Too much fuel being put into the intake manifold. Bad injectors or carburetor.

Jul 22, 2014 | 1995 Chevrolet Tahoe

1 Answer

Failed hc ppm

Use Google & study Vehicle Exhaust Emission
You'll be there for weeks,if you even understand it all
Could type in: High HC Exhaust Emissions or vehicle
hydro carbon problems
When a vehicle gets that old your close to mechanical
issues that aren't worth fixing

Jul 18, 2013 | 1993 Nissan NX

1 Answer

Fail smog test

fist i would like you to post the year make and model of the truck along with the HC ppms and NOX ppm it would be very helpful but high hc and nox can be attributed to a faulty EGR system nox is produced when the combustion chamber temperature gets too high so a small amount of exhaust is cycled back into the air stream to help cool them there are other causes but without looking at the levels its much harder to say

Dec 06, 2012 | Cars & Trucks

2 Answers

Need 92 toyota paseo to pass CA smog test ! What causes too high HC in smog test????

High HC means moisture in the system. Try driving it longer then take it to the smog shop. Otherwise it could be hard like a head gasket or easy such as a PCV not functioning. Any ways you should always drive it about 20 miles before smog check, longer when the weather is cold.

Nov 30, 2010 | Toyota Paseo Cars & Trucks

1 Answer


An old worn out engine will have high emmisions due to burning oil. Also, with age, a catalitic converter won't burn up any fuel vapors causing high emmisions.

Sep 11, 2010 | Isuzu Rodeo Cars & Trucks

1 Answer

Failed Emission Test with high NO(PPM)

Sort out the fuel/air mix and check for oil burning or replace the van.

Sep 17, 2017 | 2000 Saturn Ls 4dr Sedan

1 Answer

Wont pass emission ''hc to high" !


Jan 21, 2009 | 2000 Saturn Ls 4dr Sedan

1 Answer

Emissions level HC (PPM) too high in truck. How to fix?

Do an oil change with 20W50 oil (or one grade higher) to prevent blow by during the test.

You current oil has HC from blow by though the rings.

Do a fresh oil change will lower the HC.

Change spark plugs,wires,cap and rotor if they are over 24,000 miles

Make the smog check appointment for the EARLY MORNING. Colder air will help the fuel burn better.


Clean or change the air filter and pcv valve.

Clean Mass Air Flow sensor with CRC Mass Air flow cleaner or electronic part cleaner.


Do a quick wipe down on the wires and cap to take the moisture off.


Check spark plug wire contacts for corrosion.


Fill the tank to around 3/4.......just in case your fuel pump is weak.


Ran the truck for 20+ minutes on highway before the test.


Do not carry excessive cargo on the truck bed.

These are the little things I would do to get the HC and CO down.

Please post more information on the comment window.

Jul 16, 2008 | 1990 Ford F250

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