Hello All,
Here's a chronological summary of my smog fail problem:
- Failed smog test with following results:
RPM 1723
CO2 14.5%
O2 0.4%
HC 10 ppm (max 95)
CO 0.01% (max 0.58)
NO 1620 ppm (max 795)
RPM 2902
CO2 14.7%
O2 0.0%
HC 3 ppm (max 77)
CO 0.01% (max 0.44)
NO 1096 ppm (max 676)
- Read a lot of forum posts: high NO, low CO usually means running lean
- Checked for vacuum leaks (pressurize the intake to 10psi and soap water method)
- Intake J-boot had a tear -> new J-boot
- AOS seals were leaking -> New AOS o-rings
- Consequently -> new intake manifold gaskets
- replaced almost all small vacuum lines with silicone lines
- put in new hose clamps for a few bigger hoses
- Checked the spark plugs - tan/white'ish indicating lean mixture, replaced spark plugs
- Replaced air filter
- Noted that AFM bolt cover was drilled, indicating previous adjustment -> I didn't make any changes
- Got another smog check, failed similarly:
RPM 1760
CO2 14.5%
O2 0.3%
HC 10 ppm (max 95)
CO 0.01% (max 0.58)
NO 1449 ppm (max 795)
RPM 2866
CO2 14.7%
O2 0.0%
HC 2 ppm (max 77)
CO 0.00% (max 0.44)
NO 1076 ppm (max 676)
- Checked for more vacuum leaks
- Bottom of oil dipstick tube -> put in new o-ring
- One of the fuel injectors (turns out I damaged some of the old o-rings when putting the rail back together last time) -> replaced injector o-rings, spacers, caps.
- Can't find any more leaks.
- While resealing injectors, broke a pintle, ordered a GB rebuilt one.
- Cleaned, backflushed, replaced basket filter, and flow tested old injectors. Compared flow rate to the rebuilt one. Close enough.
- Tested O2 sensor - Didn't get very conclusive results. Probably have to replace it. Didn't replace it yet because if I'm still running lean, I don't want to damage the new O2 sensor. Have a new one (Bosch universal 15735)
- Replaced fuel filter since I had the system depressurized anyway.
- Tested DME temp sensor -> Results look good
- Verified FQS setting was at stock
Things still to do:[LIST][*]Test O2 sensor again[*]Install new O2 sensor and see if I need to adjust the AFM air bypass bolt based on the O2 sensor voltage[*]Maybe check the fuel pressure, but I don't have the right adapter, and I doubt there is an issue with fuel pressure, because the car starts, idles, and runs fine.
I would really appreciate any suggestions. I already had quite a bit of help in a previous thread here:
http://forums.pelicanparts.com/porsche-924-944-968-technical-forum/656740-vacuum-leak-question.html
I just wanted to start a new thread because that one started as a very specific question, which now expanded.
Thanks,
oreke