Another failed Cali Smog - 88 325is

[Enticive_e30]

Failed Cali smog.

1988 BMW 325is

I have changed the following:
-oil
-spark plugs
-air filter
-battery
-coolant flush
-new coolant hoses
-fixed exhaust leaks(poor welds on cat)
-swapped intake manifold gaskets (cracked)
-new intake boot and hoses


Previous owner claims:
All items replaced less than a year:
-o2 sensor
-temp sensor
-cat
-muffler

Odometer: unknown, should be around 200k

Test Results:
________________%CO2____%O2__HC(PPM)
Test_______RPM__MEAS____MEAS__MAX___AVE___MEAS
15mph_____1794__12.8_____2.6____114____43____209
25mph_____1937__14.3_____1.3____89_____32_____78

_________________CO(%)
Test_______RPM___MAX___AVE___MEAS
15mph_____1794___0.73___0.13___0.45
25mph_____1937___0.61___0.10___0.35

_________________NO(PPM)
Test_______RPM___MAX___AVE___MEAS
15mph_____1794___785___342___1930 FAIL
25mph_____1937___724___272___724 PASS


Smog tech recommended:
1. SeaFoam
2. Injector cleaner
3. o2 sensor
4. Test
5. New cat, if second test fails

Any other recommendations before I start swapping things out?

[MR 325]

How's the cap and rotor? Valves adjusted?

[jlevie]

High HC & NOX at low speed that isn't present at higher engine speed is most commonly from lean misfires, which is caused by intake leaks. A smoke test will find them and that needs to be the first priority. Other causes as possible, but until intake leaks can be ruled out it makes no sense to look further.

[Enticive_e30]

How's the cap and rotor? Valves adjusted?

Cap and rotor - how do we check if they are good?
Valves - no but it's on my to do list

High HC & NOX at low speed that isn't present at higher engine speed is most commonly from lean misfires, which is caused by intake leaks. A smoke test will find them and that needs to be the first priority. Other causes as possible, but until intake leaks can be ruled out it makes no sense to look further.

It doesn't feel like it's misfiring...

No smoke test done but I did replace all my lines and boot and gaskets. I'll tighten them up and see if I can source a smoke test


Would an exhaust leak cause my symptoms as well?

[jlevie]

It doesn't feel like it's misfiring...

No smoke test done but I did replace all my lines and boot and gaskets. I'll tighten them up and see if I can source a smoke test


Would an exhaust leak cause my symptoms as well?

You would be surprised at how bad a misfire has to be before you can feel it. So not noticing any doesn't mean much.

There 13 areas when one can have intake leaks and only a smoke test can check for leaks at any of the possible locations.

An exhaust leak won't cause these problems.

[bmwman91]

How long ago was the cat replaced? If it has been more than 2 years, then I am 99% sure that a new one will have you passing with flying colors.

I replace mine every 2 years and pass with numbers that are almost as low as a new car's. It's worth the $225 every 2 years to not have to dick with things too much to try to pass SMOG. The couple of times that I have gone in to the test with a cat that is more than 2 years old, I usually fail HC or NOx by a little bit. Every exhaust shop I have been in to have the replacement cat welded in has said the same thing, "every BMW older than 1996 runs pretty rich and burns through cats like crazy." And no, it isn't like the car is poorly maintained. No vacuum leaks, the entire fuel system is less than 6 years old at this point, the chip I run has efficient maps, etc.

E30s just run sort of rich and will burn up cheap aftermarket cats in a few years. You can't even legally put an OEM cat on in CA anymore since they are not CARB certified. Just go for a Magnaflow weld-in replacement and call it a day. Just make sure to be there when the shop welds it in to make sure that they don't cock the exhaust system and cause the muffler tips to hit the rear valence.

Good luck. Again, just replace the cat, pass with flying colors and call it a day.

[Enticive_e30]

How long ago was the cat replaced? If it has been more than 2 years, then I am 99% sure that a new one will have you passing with flying colors.

Appreciate your response!

Yea that's what I'm leaning towards. Previous owner claims cat was replaced less than 2 years ago but no records. When I picked her she was running rich and had a bad idle due to bad intake gaskets which I fixed. Who knows how long she was ran like that. She still runs a bit rich on idle(smelling unburnt gas). So I'm going to do a few more checks.

I noticed you are in the south Bay Area. Any exhaust shop recommendations?

[bmwman91]

Running rich will kill the cat super fast. I know from experience lol...years of messing with my wide-band setup and injectors have been the death of many cats!

As for shop recommendations, I am not sure if there are any here that are worth driving all the way down for. There should be plenty up in SF or South SF. If you are down here for work or something though, I usually go to World Mufflers at 966 East El Camino Real in Sunnyvale. They aren't too expensive, and they seem to do a decent welding job. Granted, I am standing right there talking to them about cars and making sure that they keep the muffler tip centered in the valence, so they probably figure I will bitch if they do a lousy weld job.

[jlevie]

An M20 engine that is running like it should be can darn near pass smog with no catalytic converter. But one that isn't running right will kill catalytic converters rather quickly. So the first task should be to put the engine into good operating condition.

[Enticive_e30]

An M20 engine that is running like it should be can darn near pass smog with no catalytic converter. But one that isn't running right will kill catalytic converters rather quickly. So the first task should be to put the engine into good operating condition.

So if no intake leaks are found what would you recommend for next steps?

[Iamalexnotyou]

O2 Sensor:
The oxygen sensor adapts the air/fuel mixture by sending a varying voltage signal to the fuel injection control unit. The sensor is positioned in the exhaust stream and actually measures the amount of oxygen in the exhaust gas so that the fuel injection system can correctly adjust the air/fuel mixture. A high concentration of oxygen in the exhaust gas indicates a lean mixture and a low content indicates a rich mixture. Thus, the signal from the oxygen sensor plays a major role in engine performance and drive-ability.
As the sensor grows old, fluctuations in idle speed and increased fuel consumption may be noticed.

Point: The rich idle may be due to the O2 sensor having gone bad.

That being said I would replace the cat at the same time due to the fact that a rich mixture can kill a cat and so it's likely they are both dead.

[jperris]

NOx is produced by high combustion temps. A properly functioning three-way cat should clean that up. O2 and HC numbers aren't high enough to suggest misfiring . CO reading is high enough that it doesn't indicate an overly lean condition. Your cat is likely junk.

@jlevie - I would agree that your statements are absolutely correct and valid in most cases. However I must say that California emissions requirements are much stricter than other states and that even a good-running engine produces excessive NOx by California standards.