HC fail-reading 907, allowed 151
 

ya so i have been searching, but no one has seemed to fail as bad on the hydro coarbons as i am. nox and co pass with no problem. i have done everything i can think of, assume that all obvious fixes have been done. need ideas...please help! TIA

come on someones gotta know something.

bump...come on. this is a caleneder truck, dont let it get impounded due to emmissions!

Did you fail at idle or on the dyno? Post up all the emission readings CO,HC,O2,NOX etc.

HC failures are almost always due to some sort of misfire. To get 907ppm it should noticably run poorly/rough.

Or have a bad catalist... :-)
The whole point of the cat is to prevent HC readings like that.

900 HC's go well beyond a bad cat. List EVERYTHING you have done so far to correct the problem so we can give you accurate info in return that is pertinent to your problem.

ok first off readings:HC/ppm- 907, 151 allowed, no good
CO%- .37, 1.68 allowed, good
NOx ppm- 449, 956 allowed, good
RPM- 2035, 3000 allowed, good

ok as far as all that i have done to it, fresh oil and filter two days ago, new plugs, wires, rotor, cap, button, 1,3,5 (passenger) side head replaced with overhauled head due to overworn valve seats in no. 5, was making no compression. motor runs great now, huge difference on six cylinders than on five. i tried to advance the timing, i tried retarding the timing, nothings seems to work. a buddy of mine is telling me incomplete burn. raw fuel cause the hc to sky rocket. i think i am gonna test all the cylinders for compression. it doesnt smoke so i am assuming the bottom end is ok(cylinders walls, rings, ect.). also brand spanking new magna flow cat to a stock type muffler. anybody? tia

running 37s have you recaled the speedo you may have a prblem there if the car thinks it doin on speed and its realy doin another

are you saying that the speedo has something to do with how much fuel is being injected into the motor

The only way a speedo has something to do with this is if they're testing for hydrocarbons on a dyno setup... I've seen a few odd cities that do a roller dyno run when testing emissions. Even then - they use the speedo on the dyno, but big tires and lack of gears can impact emissions.


A factor of 9x failure can easily be the catalist and just the catalist... Guys that remove cats typically don't realize that they just increased the amount of hydrocarbon pollution that their vehicle puts out between 500%-1000%.

Does the vehicle run well? If so, it's probably not ridiculously rich. Gasoline engines only run well within a specific range of air fuel ratios and it's actually fairly narrow.... You should recognize it via MPG, black smoke, and sputtering if it's running really rich.
(again, I'm thinking it's the cat)

sorry, but your wrong on the cat., thanks for the input though. the truck runs great, no smoke, not rough, or sputtering. like i said there IS a brand new magnaflow cat on it! but i did just get done doing a compression check, the no. 6 cylinder isnt making any compression! so theres my problem, raw fuel is what is causeing the hc levels to be so high. i am thinking about disconecting the no. 6 injector and run it like that for the emissions. btw the test is done on a dyno.

I think you need to ratbag the living piss out of it the next time you go for your re-test. GEt that cat NICE and HOT.

yeah i already do that, i hate this motor, all i need is a good excuse to do a motor swap, so yeah i wear on it daily!

You have an injector problem most likely. Pull all the plugs and see which one is wet or really black or cylinder compression. You could do an injector balance test and a compression test again.

Hydrocarbons are readings for unburnt fuel for those who did not know that. Also what would help me more is what was the oxygen reading? A 5 gas analyzer is HC hydrocarbons, CO carbon monoxide, CO2 carbon dioxide, NOx Nitrogen Oxides and O Oxygen. Post up more info if you can.

James

yeah i aready pulled the plugs, 6 was black, then proceeded to check compression, 6 was dead. thanks for the input but i figured it out already

getbenttonighy
What was the verdict after pulling the the injector for that cylindar? Did it pass?