1988 325i Failed Smog Help

[sarwaria23]

Hi I have a 1988 325i with stock motor and everything. I changed the oil and spark plugs took it to smog. I passed emissions but failed visual because the check engine light didn't illuminate when the key was in the on position (didn't even notice). Luckily, that was just a ground issue and I got it fixed in a few weeks. Went back for smog and now I failed emissions!!! HC and NO are high at 15MPH, I don't know what could have caused that, the results attached. Any help on what it could be? Only thing I've noticed is the temp gauge generally runs on the cooler side not sure if that's related.

[Sonny]

Wait the check engine light has to be on for smog?

Try driving her for an hour and do the smog again. Different location that’s busier should be better as the measuring stick should be warmed up with gunk from previous car making it easier for you to pass

[sarwaria23]

Wait the check engine light has to be on for smog?

Try driving her for an hour and do the smog again. Different location that’s busier should be better as the measuring stick should be warmed up with gunk from previous car making it easier for you to pass

No, the CEL doesn't have to be on, it has to work tho. When the key is in on position all dash light should light up but when you actually start the engine they turn off if there are no issue.

[Jaxx_]

I've often referenced the megasquirt manual that has some great suggestions:
Run the car at 200-215f - I would drive it for half an hour at least to make sure the oil and cat are up to temperature, maybe even pretty hard for a few minutes before taking it to smog
Use a plain paper air filter
Use E10 gas(or consider higher, but it'll be lean)

[sarwaria23]

I've often referenced the megasquirt manual that has some great suggestions:
Run the car at 200-215f - I would drive it for half an hour at least to make sure the oil and cat are up to temperature, maybe even pretty hard for a few minutes before taking it to smog
Use a plain paper air filter
Use E10 gas(or consider higher, but it'll be lean)

Thanks will look into that, not sure where to find e10 gas tho.

[Sonny]

1988 325i Failed Smog Help

Thanks will look into that, not sure where to find e10 gas tho.

Use the cheapest gas brand around. It usually has 10% ethanol.

The offbrand non franchise owned gas stations usually have higher ethanol I heard.

Basically pump at a unbranded gas station or if you want branded than the cheapest which should be Fastrip/Arco/Ampm

[sarwaria23]

Can it be anything technical? Like looking at the other smog posts they suggest things like o2 sensor and stuff based on the results? Like the car is running lean or rich or whatever?

[Sonny]

1988 325i Failed Smog Help

Can it be anything technical? Like looking at the other smog posts they suggest things like o2 sensor and stuff based on the results? Like the car is running lean or rich or whatever?

Well smog is free if you don’t pass so why not try pumping cheap gas and driving for a hour first and if you don’t pass then start replacing parts.
What’s the history of the cat converter is it the original one from 1988?
, does your car loose power when warmed up compared to cold ?
Because a dirty cat will let air thru when cold but when it’s hot and expanded, chokes the exhaust.

[dnguyen1963]

Well smog is free if you don’t pass so why not try pumping cheap gas and driving for a hour first and if you don’t pass then start replacing parts.
What’s the history of the cat converter is it the original one from 1988?
, does your car loose power when warmed up compared to cold ?
Because a dirty cat will let air thru when cold but when it’s hot and expanded, chokes the exhaust.

hmm...the cat is made of ceramic and coated with precious rare earth metal. I doubt that it can expand that much when warmed up to choke the exhaust.

[bradmer]

Hi I have a 1988 325i with stock motor and everything. I changed the oil and spark plugs took it to smog. I passed emissions but failed visual because the check engine light didn't illuminate when the key was in the on position (didn't even notice). Luckily, that was just a ground issue and I got it fixed in a few weeks. Went back for smog and now I failed emissions!!! HC and NO are high at 15MPH, I don't know what could have caused that, the results attached. Any help on what it could be? Only thing I've noticed is the temp gauge generally runs on the cooler side not sure if that's related.

You have a leak in a vacuum line that is causing the high HC count. Just went through that on my car, it only takes a tiny crack in the line to affect HC.
I will let someone more knowledgeable chime in on your high PPM count. Definitely do as was suggested by Jaxx and run the car for at least 30 minutes of highway driving to heat up the cats, keep the car running until you test. Change or clean your air filter thoroughly if after market.
Good luck!

[sarwaria23]

You have a leak in a vacuum line that is causing the high HC count. Just went through that on my car, it only takes a tiny crack in the line to affect HC.
I will let someone more knowledgeable chime in on your high PPM count. Definitely do as was suggested by Jaxx and run the car for at least 30 minutes of highway driving to heat up the cats, keep the car running until you test. Change or clean your air filter thoroughly if after market.
Good luck!

I would have to smoke the system to find the leak right? Could that be causing the car to run cold as well? Cheers fellow san diegan

[bradmer]

I would have to smoke the system to find the leak right? Could that be causing the car to run cold as well? Cheers fellow san diegan

Smoke is how I found the tiny leaks in the car I have been working on. Leaky O ring on the injector... I would think your thermostat would have more to do with the running cold issue.
Good luck!