smog help

[efficient]

just took my e30 to smog and it failed the 15mph. any suggestions why?

[RainRider]

Don't know why your car runs like it does but I used to run 87 octane in for emissions test to get HC and CO down. Normally run 91.

[efficient]

really?
i changed the oil.
usually i put in 87 but since the car has been sitting i put some 89 this time and drove it around for 40 miles beating on it, then took it in. didnt think that would be a factor

[RainRider]

Yes. I've been doing it since the 80's when Washington State started doing emissions testing. We stopped testing last year tho. On the 1987 325e I would toss in a bottle of gas dryer also I remember. Chev S 10 had to have clean oil too so your oil change is good.

[e30m3s54turbo]

really?
i changed the oil.
usually i put in 87 but since the car has been sitting i put some 89 this time and drove it around for 40 miles beating on it, then took it in. didnt think that would be a factor

I texted my buddy Frank. He is a mechanic for 47 years. He has 16 BMW’s from 70’s and 80’s.
This what he texted me today.

[efficient]

i think it might be the cat. i bought it used a few years back and always kind of smells gas all the time. ill change the plugs and test the wires. ill clean the cap/rotor, bought those like a year ago. the blaster coil thing is new too. i might need a new boot since the little nipple is kind of cracking. i really appreciate the replies. thank you guys!

[TobyB]

It's running rich at the lower speed...

when was the last time you did an oxygen sensor?

t
outside the RTA infection zone

[efficient]

It's running rich at the lower speed...

when was the last time you did an oxygen sensor?

t
outside the RTA infection zone

few years back.

[MrBurgundy]

make sure that FPR isn't leaking into the intake.

[e30strokr]

i got a 2 yr old cat if you need one...

[efficient]

i got a 2 yr old cat if you need one...

thanks but id like not to modify my exhaust

[e30austin]

my secret potion to getting an old BMW to pass smog (if it won't pass and/or has been sitting a while);

new CTS
new 02 sensor
new plugs (i like Bosch WR8DC)
OE catalyst (usually works best, the aftermarket ones don't last more than a couple years)
a full, fresh tank of 92 octane, preferably non-ethanol
fresh oil change
good cap and rotor
ensure no vacuum leaks

be sure that nobody has dicked over the adjustment screw on the AFM (supposed to have a blue or red cap over the 5mm allen head, they are laser calibrated and not to be adjusted, lazy mechanics will "tune" them to repair a vacuum leak they can't be bothered to fix)

do all the aforementioned and go drive the shit out of it for a good half an hour, HARD, i cannot emphasize this enough. then, while you're waiting in line, rev the engine to a steady 3-3500 the entire time you're in line. if you have a questionable catalyst, this will help to prevent it loading up on fuel while sitting in line

i've done this with multiple "problem children", cars that did not want to pass smog, and had great luck with it. i hope you do too.

good luck,

A