My '86 240 failed smog 24ppm HC over

coastbouy · Post by **coastbouy** » 11 Feb 2011, 01:48

My trusty '86 240 wagon failed smog for the first time. She was about 24ppm HC (hydor-carbon) over the limit ( the limit is 120ppm). I pretty sure the "cat" is pretty much gone. Any tips to get this baby to pass? Does using premium gas, rubbing alcohol in the fuel, changing the oil, really help? Obviously putting in fresh spark plugs is a good idea. Is any or all of these ideas enough to make the difference when the cat is not functioning?
Thanks for your ideas!!

Post by **precopster** » 11 Feb 2011, 03:57

The unburned fuel is measured as hydrocarbons in the tailpipe.

A number of reasons exist for a high hydrocarbon count. Interestingly what was your nitrogen oxides and carbon-monoxide counts? Are these measured? Were these also high?

Yes a bad cat will contribute to high readings, however fouled plugs, clogged injectors, leaking valves/valve seats and low compression can also greatly affect the outcome. All of these factors will contribute to a partially burned fuel/air mixture.

Can you highlight the general condition of the engine, ie. oil use, smooth idle/performance, if you have run an injector cleaner, age of plugs. Is your car used for high mileage trips regularly or mostly short trips?

If you can give a better picture of your car's overall condition that would be great.

coastbouy · Post by **coastbouy** » 12 Feb 2011, 08:21

Hey thanks for getting back to me!
the car is used mostly for ten miles per trip (to and from work) the car does not use a lot of oil and idles well. I have not cleaned or replace the spark plugs for two years or used injector cleaner. Here is the #s from the smog test:
RPM: 761 %CO2 (13.2), %O2 (2.0), CO(%) (.50)
RPM: 2498 %CO2 (14.4), %O2 (0.3), CO(%) 0.34
With the HCs: the at 2498 RPM the car measured 14 PPM
I would say the car is getting close to end....I am currently looking for a used 850/earlier V70
Thanks for your help!
Joel

Post by **billofdurham** » 12 Feb 2011, 12:21

Too many short journeys will gum up the works. Take the car on to a good road and open it up. Don't be surprised if you see a cloud of 'smoke' behind you. You should never take a car for a smog test unless you have given it a good, hard run to clean out all the rubbish.

Bill.

Retired MVS Contributor · Post by **Retired MVS Contributor** » 12 Feb 2011, 14:03

coastbouy wrote:Hey thanks for getting back to me!
the car is used mostly for ten miles per trip (to and from work) the car does not use a lot of oil and idles well. I have not cleaned or replace the spark plugs for two years or used injector cleaner. Here is the #s from the smog test:
RPM: 761 %CO2 (13.2), %O2 (2.0), CO(%) (.50)
RPM: 2498 %CO2 (14.4), %O2 (0.3), CO(%) 0.34
With the HCs: the at 2498 RPM the car measured 14 PPM
I would say the car is getting close to end....I am currently looking for a used 850/earlier V70
Thanks for your help!
Joel

I don't see anything about the air filter...Much to my amazement, I have seen this overlooked a bunch...

coastbouy · Post by **coastbouy** » 23 Feb 2011, 07:35

My car almost passed smog yesterday. I missed passing by 4PPM HC. The limit is 120PPM HC. This was after changing spark plugs, cap and rotor, removing the air filter, running injector cleaner through the fuel system, filling the gas tank up with premium (I'm not sure that did anything) and driving the car fast for 25 miles. Again I'm pretty sure the "cat" is dead, and I'm hesitant to invest in a new one. Any other tips to squeezing out a few more PPM HC.
Thanks for your help!
Joel

Retired MVS Contributor · Post by **Retired MVS Contributor** » 23 Feb 2011, 08:58

coastbouy wrote:My car almost passed smog yesterday. I missed passing by 4PPM HC. The limit is 120PPM HC. This was after changing spark plugs, cap and rotor, removing the air filter, running injector cleaner through the fuel system, filling the gas tank up with premium (I'm not sure that did anything) and driving the car fast for 25 miles. Again I'm pretty sure the "cat" is dead, and I'm hesitant to invest in a new one. Any other tips to squeezing out a few more PPM HC.
Thanks for your help!
Joel

Has the oxygen sensor been checked?...240's are extremely reliable, running well over 200k...

Post by **precopster** » 23 Feb 2011, 14:22

Run the injector cleaner again. This time take the car for a spirited drive just prior to the re-test; just don't show them your blue coloured discs

As insurance the O2 sensor will probably get you there. Try cleaning it with carby cleaner if funds are low, but this may not work if it has done high mileage. Don't leave that filter off for long eh?