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Discussion Starter · #1 ·
I am trying to pass smog in my 2000 Z3m coupe (s52 All stock with 67k miles shouldn’t have many worn down parts. Also cold start is rough and a bit low in rpm’s (900 down to 700) my only thought to what might be causing it not to pass

Things I’ve done to ensure nothing is wrong:
-cleaned and checked operation of ICV
-cleaned and checked secondary air check valve
-ensured pump comes on and is pumping air properly
-replaced both upstream 02 sensors (figured they might be “slow”)
-checked that vacuum line running to check valve is intact and holding vacuum
-replaced intake boot and icv hose
-sprayed carb cleaner everywhere around any areas that might have vacuum leaks to no avail

the only lead I might have as to why the monitor won’t pass is that on cold start (when the test is occurring) the car only rides up to around 900rpm and drops slowly to around 700rpm, also shakes and almost sounds like it misfires for the 33 seconds that the 2AP runs. I’ve read it should be up around 1300rpm but my ICV is clean and free notlocked up in there.

any ideas? I’ve gone through about 5 or so full drive Cycles and cold started the car 20+ times.

could it be the maf? (I believe it’s original)
Could a new ICV fix it (do they go bad even with the flap being free inside?)



TLDR: No CEL, no vacuum leaks, bone stock, secondary air smog monitor won’t pass but won’t fail, constantly on not ready.
 

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2004 330Ci 115k miles
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16,314 Posts
Read the trouble codes, short term fuel trims, long term fuel trims, and MAF value (in grams/second) at hot idle and report back. If you don’t have a tool for that, get OBD Fusion.

Do a smoke test to find vacuum leaks. Carb cleaner doesn’t cut it.
 

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Discussion Starter · #6 ·
Instead of posting a bunch of screen shots, how about just posting the relevant data?
My bad, not used to the forums, basically the 02 values jump around a lot from negative to positive, short term at least. Not sure what to be looking for in terms of the values but I didn’t know if typing them out would defeat the purpose of seeing exact with their connotation
 

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2004 330Ci 115k miles
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16,314 Posts
Here is what I extracted from all those screen shots.
  • trouble codes: not shown
  • short term fuel trims: bank 1 is -3.9%, bank 2 is +2.3%
  • long term fuel trims: bank 1 is +8.6%, bank 2 is +7.8%
  • MAF value: 3.33 g/s (0.44 lb/min)
All fuel trims should be close to 0%, your long terms are too high indicating vacuum leaks.
A MAF value of 3.33 g/s is about right for your engine.

Looks like this is your SAP system?
Pretty simple, just the pump and valve.

SAP system injects extra air (O2) into the exhaust at cold start for less than 2 minutes. DME expects this extra O2 to drive the pre-cat O2 sensor voltages low and will not set SAP emissions monitor to pass unless this happens.

A cold start log with OBD Fusion will show exactly what is happening.
 

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Discussion Starter · #9 ·
Okay I inspected the system and everything seems to be working I’ll have to take another look, thank you for the help. I will get obdfusion as well seems helpful towards diagnosing these sorts of things.
 

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Discussion Starter · #10 ·
I removed all the duplicate pics and the ones with no useful data.
Moved to E36 forum.
I smoke tested the car, no luck. Sap pump is working and check valve has vacuum and opens properly, which leads me to believe problem is 02 driven? Maybe icv isn’t working properly? The cold start only jumps to about 900rpm and shakes a lot then dips to 700ish after 30 seconds and stops shaking. I cleaned ICV and it moves freely but maybe it’s electrical?
 
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