So my attention has been away from the ST for awhile, it happens when you have several projects
Thought I'd share my recent CA Smog experience with my 1985 e28, which has increased my knowledge around this cloud of emissions mystery.
For those that want to read about the FiST having to go into visit the California (BAR) Bureau Of Automotive Repair State Ref.
http://www.fiestastforum.com/forum/threads/3074-koozy-s-ST?p=177708&viewfull=1#post177708
Now back to the e28... trying to get simple common sense info from smog techs was frustrating. My experience has been that many don't know, want to share or take the time to diagnose even for a fee and instead are quick to guess, which exacerbates confusion. I'm not surprised why people give up on their older cars and send them to the crusher, many mechanics fail to properly diagnose and owners just throw in the towel. I inquired shops and mechanics that specialize in classic BMW's and was disappointed with their lack of emissions knowledge. I found this surprising because if they're in the business of restoring or maintaining classic cars you'd think having knowledge and being well versed with emissions is paramount for post 1975+ vehicles.
It was time for the bi-annual CA Smog test, which it has passed the last 3 times over the last 6 yrs. This year it failed and pretty bad. Here's the test result that deemed it a "gross polluter" with excessive high NOX values, which usually indicate high combustion chamber temperatures. Personally I don't care for the moniker as I don't ever plan on selling the car and the status only means that it failed at that time. It doesn't mean that the car can't be brought up to spec to pass with flying colors, which is what matters in the end, at least to me.
After doing some research it seems that an e85 blend is what may have caused the NOX to go way out of spec. I hadn't done this in the past, but I put in 2 gallons of e85 and the rest was 87 octane in the tank to help, but it appears to have done the opposite. The car is pre-OBD2 with only one O2 sensor before the catalytic converter and can't compensate for the higher than e10-15 blend. The CO and HC were great, but the excessive e85 blend significantly increased the NOX emissions.
Test #1
I replaced some of the rubber intake plumbing that showed signs of wear and possible leak issues which would also drive up the NOX values, checked the spark plug gaps (Bosch WR9LS (.028) which had 20k miles on them but still looked good. I cleaned out the Idle Air Control Valve, used half a can of the Seafoam spray into the intake to help clean out intake/valve carbon deposits and added a can of Techron into the tank. After the tank was depleted of the Techron I filled it up with Shell 91 octane, which has Nitrogen in it for cleaning but apparently does not contribute to elevated high NOX emissions. Here are the results from the 2nd test. So, the 15mph NOX results significantly improved. I attribute this to not having any e85 in the tank. However the 25mph NOX value was still high and out of allowable specs. I suspected the O2 sensor being the issue, which was 5 yrs. old and had 40k miles on it.
Test #2
After changing out the O2 sensor and filling up with 91 octane I head back for test #3 and it failed both 15 and 25 mph tests. The 25mph test significantly improved which showed that the new O2 sensor helped. Here are the results, but still indicated that there's still a problem. The car still has the OE catalytic converter with ~200k miles, but I did not suspect the converter being the issue because for test #2 the 15mph test results were great. Thinking back I suspect the car was hot after idling too long as the smog tech was prepping, he probably thought it was helping to get the catalytic converter warm but I don't think idling would do that. This smog test center was different from the first place and had the front of the car into the shop with no circulation and no fans placed in front of the car during the rolling dyno emissions test. After the results the techs were telling me that the catalytic converter was too old and was probably the issue. They even went so far to do a back pressure test and confirmed that the converter was plugged.
Test #3
I didn't believe that the catalytic converter was dead just yet because the HC and CO results were great. Sure I could throw on a new catalytic converter which would probably make the car pass, but I wanted to get to the root of the cause and not a bandaid. The OE cat is known for being very stout and better than any aftermarket unit if it's working right. Before I was willing to get a new DEC 50 State Approved Converter I was going to at least give the car it's best shot before doing that. I decided to drain the fuel tank to clean it and the transfer pump out making sure no gunk was in there. New parts include a new fuel filter, new WR9LS spark plugs, all were perfectly pre-gapped at .028, new Bosch distributor cap and rotor, flush out the cooling system and install a new thermostat with Prestone LongLife and Hyper-Lube Supercoolant additive to help bring down the coolant temp. The Castrol High Mileage 20w/50 With Mann filter were recently installed so I left that alone. These were the things I was willing to try before getting a new catalytic converter. Having good results with 91 octane with the previous test I decided to continue to use it for the next test. I also didn't want to have too many variables if things went awry. I normally fill up with 87 octane and have historically passed smog checks in the past with it, but with the high NOX values I wanted something to help keep the combustion chamber a bit cooler. Here are the results, note the slightly higher but well within specs HC value probably due to the 91 octane. The car went back to the first smog place in which the car has to be backed into to shop to get on the dyno roller, leaving the front of the car out of the shop with fresh ambient air. This time I chose to bring the car in early in the morning when the ambient temp would be cooler. My focus was to bring down the NOX values, as the other two perfect values for HC and CO had some room to give for better NOX numbers. The tech also put a fan in front of the car this time to help with cooling and simulate being on the road.
Test #4 Passed
Final Notes to self: Don't have more than e10 in the fuel tank for the emissions test. Go early in the morning, make sure the car is in perfect tune before considering a new catalytic converter. Don't patronize a smog test center that doesn't give you car a fighting chance like having the car point into the shop with poor air circulation or not using fans during the rolling dyno tests.
Somethings I should consider having done before the next test: R&R the fuel injectors and get a new airflow meter.