California Smog Check Fail

[jmwvtlax]

I am the proud owner of a manual 525i 1993 with 222000 miles. Recently I moved to California. I took my car for a smog inspection and it failed. There are 3 tests that take place at 15 and 25 mph: Hydrocarbon ppm, NOx, and CO. I passed NOx and CO no problem, but I failed the Hydrocarbon (HC) ppm at 15 mph severely and barely failed at 25 mph. At 15 mph (2nd gear) the limit is 83 HC ppm; I got about 220 HC ppm. At 25 mph (3rd gear) the limit is 50; I got about 54 HC ppm.

About a year ago, I replaced the O2 sensor after receiving that fault code,rebuilt the VANOS, and replace the spark plugs. The car has the stock computer chip and only sees mobil 1, everything that has been replaced is a Pelican part product or OEM and still has great performance overall (30 mpg highway!). To me it sounds like an issue in the fuel injection system (running too rich). I believe the cat, though it may be old is still doing it's job.

Can anyone please confirm or advise on my current situation?

[JhwShark]

Please post all results for both speeds:
HC
CO
NO

Good NO and CO means that you most likely have an OK cat and O2 sensor with A/F also probably OK.
Also, and more to your issue...high mileage cars can have issues getting a full burn. Using lowest octane in CA is best for smog tests. Since you have modest HC fail you are most likely not burning all the fuel. Low Octane has a flash point that will burn off more/most of your fuel during the engine cycle while higher octane may not burn completely in time...leaving some residual HC for the tester.

Drive the car for a good bit of time before the test as well.

[one4all333]

I have a 1994 740il with 208k miles that just failed CA smog. Passed all tests except HC (PPM) at 15 MPH. My reading was a 72 and Max allowed is 56. I am thinking new plugs, oil change and getting engine nice and warm prior to test will help...any ideas? (

My Test Numbers
15MPH %CO2 - 15.2, %O2 - 0.0, HC (PPM) - 72 (MAX 56), CO% -.12, NO (PPM) - 117
25MPH %CO2 - 15.1, %O2 - 0.0, HC (PPM) - 25 (MAX 45), [/B]CO% -.08, NO (PPM) - 45

[JhwShark]

Since all Pass except for the HC at low rpm's...
Yes, change oil, plugs may be OK but change can't hurt, and always get car to operating temp for some time before pulling into the SMOG check.

Also, on old cars, rings are worn a bit...so use low octane. It has a low flash point in comparison to higher grades. This means that you will burn more if not all the fuel in the combustion chamber, higher octane burns hotter but takes longer to burn all the fuel...so the logic is you burn it instead of un-burnt going down/out the exhaust. This is what I did when I missed the last test.

[one4all333]

Just wanted to say thanks for the advice....I changes the plugs and Oil, then ran all the gas out (had fuel injector cleaner in it), then put lower octane gas in, and made sure the CAT was nice and hot before testing....passed with flying colors.

Thanks Again

[ppjonydi]

what do you mean by a lower OCTANE? I know it is 87, 89, 91. Can you use an 87Octane on a bimmer?

[JhwShark]

Originally Posted by ppjonydi

what do you mean by a lower OCTANE? I know it is 87, 89, 91. Can you use an 87Octane on a bimmer?

Sure. It cost less and most important for a SMOG test...it helps you pass in certain cases! It may cause you to ping if you have a higher compression engine, but for passing a SMOG test why not. Then you can use what ever suits your car and drive style...

[Jared at Pelican Parts]

Higher octane gas actually burns SLOWER.

1990's BMWs will run fine on 87 octane. They have knock sensors.

And yes, probably a good idea to use it to try and pass smog.

[ppjonydi]

Thanks much for the info, Another thing, how about the type of oil needed for 1993 525i, which have a higher mileage( 297xxx) miles?

[Jared at Pelican Parts]

I would just run whatever oil you have always run. Don't use any of that high mileage crap.

[ppjonydi]

Hi, I know there are different types of spark plug for 1993 525i BMW. Does anybody know what is the measured resistance for BOSCH 4417 tip to tip? I normally measured them before installation to eliminate headaches. I'm used with NGK plugs, but this 4417 I obtained, when measured give different readings. 3 of them have 4K, 1 with 10K, and the other 2 have no resistance at all. I will appreciate your help. Thanks.

[Jared at Pelican Parts]

Originally Posted by ppjonydi

Hi, I know there are different types of spark plug for 1993 525i BMW. Does anybody know what is the measured resistance for BOSCH 4417 tip to tip? I normally measured them before installation to eliminate headaches. I'm used with NGK plugs, but this 4417 I obtained, when measured give different readings. 3 of them have 4K, 1 with 10K, and the other 2 have no resistance at all. I will appreciate your help. Thanks.

4417 are Platinum plugs. You don't want to use those in your engine. Use Bosch FR-7-LDC+

[JhwShark]

Originally Posted by jared at pelican parts

4417 are platinum plugs. You don't want to use those in your engine. Use bosch fr-7-ldc+

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