grrr... emissions failure. advice?

[sinistral]

first emissions test required since buying the wagon 2 years ago this week...

both HC and CO were high.

this indicates running rich, right? thoughts on how to proceed?

'85 TBI (i thought the ECM was supposed to take care of all this smog-laden junk?)

thanks in advance.

[sly]

check for codes... the ECC-IV CFI should give you something... if there's nothing... cats are probably dead.

[gadget73]

They almost never give codes for bad oxygen sensors, and the failure mode is usually to run rich. I'd also be replacing all of the vacuum lines if you haven't. Vac leaks will tend to make it run rich. Check the timing too.

[sinistral]

check for codes... the ECC-IV CFI should give you something... if there's nothing... cats are probably dead.

will there only be codes w/ CEL/MIL?
no light triggered -- plus the one time the light was on, nobody had a reader for OBD1.
(luckily turned out to be low coolant heat related)

[sinistral]

They almost never give codes for bad oxygen sensors, and the failure mode is usually to run rich. I'd also be replacing all of the vacuum lines if you haven't. Vac leaks will tend to make it run rich. Check the timing too.

thanks... guess i'll be poking around under the hood this (frigid) weekend.

[gadget73]

There is no check engine light on an 85. The red Engine light means you have no oil pressure or its badly overheated. I refer to that one as the Replace Engine lamp, because if it came on, you probably need a new motor. The computer one (if it had one) is amber. Almost nothing actually sets it anyway. In my experience, basically unless the EGR valve is being stupid, that light won't come on. It can still set a bunch of codes though, so its worth checking.

[merc91]

put a drain plug in the tank, drain the gas, pour in alcohol, pass the etest (even without cats in my case), drian the alcohol, gasser up and keep burning them peoples eyes driving behind ya.

But ill second with the others with a vac leak being able to cause quite a rich condition, also since its never that easy, I would pull all the spark plugs to check for a black 1 indicating a stuck open injector for sefi cars, or in your case possibly a bent/burned valve or head gasket blowout (2 black plugs next to eachother if your oil and coolent are staying seperate) causing low compression or having a dead plug will huff out quite the co and hc... with 8 cylinders and a low compression ratio, it can be quite possible to be running on 7 cylinders and not notice... if your failing by a substancial amout, the plugs will tell the story.

Ofcourse if you jussst barely failed, bring the car to the test as hot as you can and tell them you have to be somewhere or whatever so they dont dick around until your parked car has cool cats again, go with regular gas and a small amount of acetone (theres formulas but around 75ml for a whole tank of gas) The acetone breakes some of the gasolines surface tension and does allow for a more complete hotter burn.

[sinistral]

thanks, merc91 (wow, nice ride ya got there -- probably not too many NOS GMs around, eh?)

i wonder -- it was frigid cold yesterday and i live only a few blocks from the testing station. if i would've been thinking i would've hit the highway for a bit to warm up first.

i'll pull the plugs tomorrow and check for any obvious vacuum issues.

i did find out that AAMCO will still check OBD1, so i'll give that a shot on monday just to be sure.

[merc91]

haha thanks, yeh shes 1 of a kind around here. Despite being a normally healthy 20yr old ive been really sick for the last 8 months with something causing scarring in my brain but on my good days ive got the whole rear end and suspension out of er and building an all new custon setup to polish off the 1000hp built drivetrain

With a bunch of snow flying around here I know the cold is a beeeyawch to be screwing around trying to get at spark plugs but I think they will be a great indicator as to what your problem is. If you have a problem cylinder, a plug will show it by being black, and if you have an issue with the various electronics managing the air/fuel ratio... all your plugs will show you that by all 8 being a dark goldish brown. Having low compression or an arcing plug wire on 1 cylinder will cause it to exhaust a rich condition, and the ecu will get a rich reading on that side of the motors o2 sensor and lean out that whole side since it cant differentiate the 4 cylinders, this will cause a slightly lean condition in the other 3 which raise co and nox readings aswell.

Around here we have a test at idle, and a test at i think 2500rpms and have to pass hc and co emissions at both speeds. Do you know by how much each was over the limit and at what rpms the test was done?

in ontario if we fail twice and have a repair quote over $400 we can opt not to repair the car and pay to fail another etest and pay a $100 fee to get a conditional pass, which is as good in every way as a pass... guess who trippled the hc limits this past summers etest haha. If this isnt a hopped up motor though it would be good to get it running better to pass i guess.

[GM_Guy]

thanks, merc91
i wonder -- it was frigid cold yesterday and i live only a few blocks from the testing station. if i would've been thinking i would've hit the highway for a bit to warm up first.

Absolutely. On an older car where things are no longer 100% efficient, heat makes a big difference, especially for catalytic converters that may be getting close to end of life, or an engine that is slow to get to operating temperature (and with that the computer going into closed loop)

Alex.

[sinistral]

well i pulled the plugs yesterday and if anything it looked like the motor is running a bit lean. at least they were all consistent, and dry.

i went ahead and replaced the O2 sensor (which was a PITA). it might be my imagination, but it seemed like the car was running better afterward. i'll run by AAMCO today and see if anything comes up via OBD. while i was underneath the car i did notice that one of the cats is rusting through in pretty bad shape -- hoping that is not the culprit. all vacuum hoses appeared to be connected.

btw, my chilton manual says to check the underhood sticker for timing info, but that sticker is long worn and illegible. what do you recommend?

the high temp today is supposed to be high teens, so i probably won't bother taking it back for another test yet until the ambient temp bumps up a bit (i've got until next monday). i'll definitely drive it around and get it nice and hot before.

results
HC : 9.79 (limit is 2.5)
CO : 169 (limit is 20)
NOx passed

from the test documentation it looks like they run it up to 35mph, back it down, then up again to 55mph over a 4min period.

merc91, hope you get to feeling better. chicks dig scars, just tell 'em yours are all inside your head.

[merc91]

hmm well thats good the plugs are all the same and looking a bit lean is perfect for these cars (not actually running lean). Hopefully the new o2 helps out, and as for timing, stock is 10* I believe, and the cars quite like 12-14* which will help start the burn that bit earlier and infact does lower hc a tad. Especially with it being cold you would notice surging and runnin like crap if you had any sizable vac leak which sounds like your good to go there.

If you dont have an idle portion on the etest to pass than this doesnt apply, but bumping up the idle screw a little bit to raise the idle substancially improves the emissions since emissions at idle are usually 4x that of cruising speeds.

Here the limit for my 91 was 52ppm hc, and 2ppm CO. I guess you guys must have a different measurement system over there for them emissions. Regardless, your wayyy over ehh, if your plugs look nice than I would say them cats are as done as cats can be.

Thanks man, ive always been more into mechanical stuff and go fast toy building than girls... or anything else, and let the hotties come to me (which the laws of reason deem impossible) but no joke, they are poppin up left and right the last 8 months hahaha.

Good luck passing, I facken hate etesting time of year lol...

[sinistral]

units = GPM (grams per mile)

[sinistral]

well i had to go to three different AAMCOs before i was able to get a reading...

the following codes were pulled:

31
18
41

what does this tell me?

i'm looking to go back for the re-test on friday -- O2 sensor replaced and verified timing is right about 12˚ or so.

also, my tank is about empty -- should i fill w/ some premium before going back for the re-test, or would that not make any difference?

thanks.

[gadget73]

18 is the problematic one. It means the SPOUT circuit is open, so either the connector is missing, or there is a problem with the ignition module or pickup. Or theres a wire broken somewhere in the harness. Either way, if the timing is not advancing properly its unlikely to pass smog or run worth a damn. This is a stored code though, so I'd try clearing it first and see if it comes back. it may be old crap.

31 is an EGR problem. It means the sensor shows the valve has closed too far. Basically that cant happen, so either the sensor is bad, or its loose and not positioned correctly.

41 is system lean, so either its actually running lean or the O2 sensor is being retarded. Since your emissions results point to the engine running rich, I'm going with sensor being retarded.

Something to be aware of, there are 3 sets of codes in these cars, so depending what test was run, it means slightly different things. There is a key on engine off code, immediately following that you get stored codes. Then there is a key on, engine running test which is probably more useful. Ideally you want all of the codes to see whats going on. If the codes you got were engine not running, they're quite probably old stored codes that can be erased since they don't mean anything now. The O2 sensor code could very well be from before you replaced it. It won't go away unless the code scan is interrupted or the battery is unhooked.

http://oldfuelinjection.com/?p=13 explains how to scan it for codes, and there is also a link there for what the codes mean.