High Hydrocarbon!! readings...(edited!)

[treeZ24]

about 2x the limit lol....

any ideas... 2.8L 350000km's on it.. motor is fine, i 'm thinking either egr valve , pvc valve etc..

the cat looked fine when i put it on the car.. although its getting a few years old now........ and there's no codes

edit.. i just checked the vacume on the egr.. isnt it supposed to stay open when running at higher rpms?

[ProjectMM]

not always, what is the year?

as long as you have a signal the EGR should work, it could be pluged up but most likely it's working. put the reading on here and the year make and modle.

[treeZ24]

89z24... its vacume controlled....

[geoffinbc]

Only 1 thing causes NOx. Very high combustion temperatures. So make sure the EGR functions. With the car idling use your hand to open the valve by pressing on the diaphragm. If idle changes then the gasses are getting to the engine. Next you need to make sure it gets a vacuum signal and that the soleniod is working. Also what operating temperature did you go through the test at? If you car was over heaing or very hot then it would cause high NOx

The Cat converter will have no effect on NOx emissions

[treeZ24]

ahahaha.. damm i can't win..

i replaced the o2 sensor.. the egr valve and went for aircare again.. wouldnt you know i told the guy to put it in 3rd gear instead of 2nd..(1800 rpm instead of 2800) and my Hydrocarbons are high now instead of the N0x

[geoffinbc]

LOL well thats no good is it. Now what operating temp was the car at? Also did you ever shut it off. You cannot do that you need to leave it running.

[treeZ24]

nope i left it running in the lanes... it was at normal operating temp.. around 80*c... this is driving me insane..

[TheProfessor]

how many miles is 350000 kms

[sharkey]

its over 240 000 if i rmember right

[geoffinbc]

80*C is this for sure? Or from the stock guage? Needs to be higher than that. Should be around 93 for optimum burn.

With a high miler try running it through with an ethanol blended gas. Also do not rule out the ignition system. My friends 90 Cavalier failed. We took it back and put in new plugs and wires and it passed.

[treeZ24]

i dont remember what it was exactly.. but i took it for a burn on the highway before and ran it pretty hard on the road before i took it to aircare.... it sat above the 70*c mark so i just assumed it would be btw 80*c and about 90*c.. whatever the thermostat is .....


ACTUALLY.. the engine has been heated quite badly in the last month..up to 125*c atleast... O.o the gasket on it went and it was cold when i was running it on the highway.. didnt notice and it heated up really freakin fast after i sat at a few lights...!!!!! shut it off.. got some water and replaced the gasket.. but maybe i should replace the thermostat ??

[sharkey]

talked to my dad today brad, he said its the cat. if you have an infered temp gun, check the temp at the front and back of the cat. the back should be way hotter (400-500*f at the back). if its close to the same, the cat is toast for sure. he said it sounds like a section went dead in the cat, and that will cause high hydrocarbons.

[geoffinbc]

Yes a bad cat will cause high hydrocarbons.

[treeZ24]

yeah it will.. but i dont think that a back to back reading like that would suddenly show that the cat just died.. its possible for sure but i think thats too much a coincidence for that to happen.. another memeber suggested getting the coil packs tested.. i'm giong to do this asap as well because it may be an intermittant electrical problem.. ... gotta check those plugs too!!!!

coil pack relocation asap , new wires.. plugs, pvc valve, thermostat.. and replacing the upper gaskets to make sure i dont have a vacume leak..we'll see after that

[sharkey]

the reason your hidrocarbons are were low before was because the egr wasnt working. its common when the nox is way up for hydrocarbons to be low. when you fix the nox problem, the hydrocarbons go up. and hydrocarbons are caused by the unburnt fuel in the exaust gasses not being burned up in the cat. timing can have a play in this to, but yours is fixed, so no worries there.