my 300e-2.8 flunked emissions
 

previous owner thought she would do me a favor and tried to get the car inspected (don't ask) before i picked it up. well - it flunked emissions. when i did pick it up tonight i smelled the hydocarbon rich aroma of the exhaust but otherwise it was ok. i had road tested it and it had good power and was smooth. so i took a calculated risk and told her not to worry about it. the car had not been tuned up in a while and the owners were not particularly car savvy.

funny that my checklist thread had gotten around to spark plugs. i figured i was gonna change those right away and also check the air filter so it suddenly became first on my agenda. this had happened to me once when i didn't change the plugs and have never failed when i did change the plugs. was i being foolhardy? i'm gonna throw a bottle of chevron injector cleaner in there for good measure although i doubt that's it because it had plenty of power on the drive home. what else am i missing?:rolleyes:

This last inspection, my truck was visibly smoking. The guy would not check it while I had visible smoke. I fixed that problem by using Mobil 1. I then got a test and registered 277 out of acceptable 220 HC. I then put in a bottle of Berryman 12 fuil additive (from Walmart, I believe). The truck passed with 62 ppm. You may need to go to the shop and have your A/F ratio adjusted, also, on the benz.

just checked the readout - it failed hc at 167 (standard is 100). nothing else, no visible smoke, no nothing. the one time this happened to me it was the same problem and i changed plugs and came right back - the guy thought i was kidding because it hadn't been 30 minutes yet. passed with room to spare. hope it's the same deal...

I think I've seen stuff they actually sell that you put in before a smog check, and they advertise it as such.

Not sure..

I would use a good fuel cleaner, change plugs, maybe air filter, and go again....

Alon

i've seen those at pep boys - "guranteed to pass or double your money back". you throw it in your tank, use up the entire load of gas then fill up and take the test. i'm sure it will work but am not quite that desperate yet. i would like to pass legit if i can and i need the tune up anyway. thanks for the input...

As you try to dance around the test spec, let me warn you that your model should not even get close to failing that type of test.

You didn't mention which state or which type of test but no way will that car with its feedback control lambda system and three way cats ever fail that test; if even close to running properly. (and with a fully warm catalyst)

A car that passes that test with only a set of spark plugs added, has serious problems.

don't scare me now. it's in new nj with the new strict controls. it's registration is current and i think the last tune-up might have been 2 yrs ago. can you qualify what you mean when you say "A car that passes that test with only a set of spark plugs added, has serious problems"? if the plugs are bad, will the lambda feedback control and three way cats clean up the excess HC?
i know that copper plugs go south within a year, because it happened to me. i mean i didn't have all the fancy emission controls on the other car but it was the exact same sort of readout and the new plugs fixed it. everything else passed - smoke and CO. it's only the HC that flunked which is kinda indicative yes?

Steve, does not JS's car have an A/F adjustment? It is possible to get a vehicle completely out of whack with one maladjusted! A simple turn of the screw will get everything back under control.

In addition, if a vehicle passes with a couple of plugs replaced, I would say that the vehicle does not have serious problems but the plugs sure did.:)

Of course you must understand, I look at this from a different point of view.

The 2.8 car will be EFI, I don't remember if it is LH (separate ignition with dist cap) or HFM (integral ignition, with multiple coils waste spark ignition). Neither system has any external adjustments. They are totally self-learning, self correcting both in mixture and timing and engine idle speed. NO ADJUSTMENTS.

If spark plugs matter to the emissions of these systems, the cars most serious problem is a lack of attention from its maintenance manager. Plugs are still recommended (except in Ca.) at 15k intervals. They easily go the Ca. recommended 30k and probably much longer. I don't happen to be on the group that thinks you can improve this motor with plugs. At least not until they are just screwed.

If plugs really make a difference, it will be because they are being hurt by a condition in the cylinder - the other type of serious problem. Problems such as leaking injector, leaking valve guide seal, too much carbon from long term valve guide seal leak, and in the end compression problems could occur that plugs could help.

A proper maintained car will not have any chance of failing these tests without a problem. Plugs can only mask the problem. If there is no problem and plugs help the problem then there is a problem.....with maintenance!

Just my opinion , of course.

Run down to your local GM dealer and grab a can of "Top End Cleaner" and use it, along with any other advice Steve gives you. Cleaning out the carbon around the valves and in the cylinders will improve your emissions and your inline 6 will love you for it.

p.s. and please don't listen to Running Too Hot's doomsday prophecies of using this product.

It does work.

Good luck,

-Paul-

ahh operative word "properly maintained". last MB service was '99. then the local gas station mech just changed the oil as far as i can tell which is all i wanted to make sure off.

i misunderstood steve's reply and see that there is no adjustment for A/F ration which is usual on many cars these days. the car i had this same situation on was a little mitsu turbo that had a fairly sophisticated head (for its time) that had three valves per cylinder. the third valve was there to ensure a clean burn. it also didn't have an a/f adjustment. i remember the reading after i changed the plugs after it failed was way under the limit. i just draw similarities because that car also had limited use throughout the year with trips typically < 5 miles. i religiously changed the plugs every time i brought it in for inspection in the 9 yrs i had it and it never failed except for that one time.

bottom line, i guess my options are limited. i'll change the plugs and take it in for inspection. then i'll just have to go from there.

thanks for all the input.

just an update on this. after two tanks of gas with techron and a new set of bosch supers i finally brought it into the inspection station. end result - passed! :D the failed HC reading was 160, the new reading was 8 (yes 8!)...

ps. the plugs were relatively clean, no oil or carbon when i pulled them but the gap was way off.