Author Topic: E30 318is failed smog!!! (Read 3907 times)

Bimmer805 · « **on:** January 03, 2011, 08:08:44 PM »

Ok so i finally took in my car to go get my car smogged and it failed which ruined my whole day. the guy said he can check to see whats the problem for 90 bucks seems quite expensive for me. and he said if i get it repaired there he will do a free re-test on my car well here are the numbers PLZ!! let me know what could be the problem?

15mph: HC measures 170 and the max allowable is 124 FAIL
CO measures .79 and the max allowable is .78 FAIL
NO measures 2002 and max allowable is 815 FAIL

25mph: HC measures 90 and max allowable is 98 PASS
CO measures .45 and max allowable is .66 PASS
NO measures 731 and max allowable is 754 PASS

they did the same test at 25 mph and it passed but it didn't pass the 15mph test I just want to here your guys opinion on what could be the problem. i look forward from here you fellas or gals thanks...

DesktopDave · « **Reply #1 on:** January 03, 2011, 08:30:58 PM »

When was the O2 sensor last changed? Does the car run cold, warm or just right? High NOx is usually due to a lean mixture.

Do a stomp test, see if you get any codes.

Bimmer805 · « **Reply #2 on:** January 04, 2011, 12:09:19 AM »

i dont know when it was last changed. the car usually run in between the quarter and half way mark of the temp guage.

DesktopDave · « **Reply #3 on:** January 04, 2011, 07:28:06 AM »

That O2 might be your whole problem. They do wear out over time. You can get a cheap 4-wire Bosch from any early 90's Ford V8 IIRC, same part with a different connector. Splice that in with solder if possible...those heater wires pull a lot of current on startup.

You might have a lazy thermostat too. Your car should be pretty close to the halfway point most of the time.

Another cause of high NOx is leaks in the intake hoses. Spray them down with throttle body cleaner while the car is idling. If the engine changes it's idle speed when you spray a particular hose, you know you have a leak. Definitely check that fat hose under the throttle body. I've seen them crack clean in half.

colin86325 · « **Reply #4 on:** January 04, 2011, 08:18:34 PM »

I had a nice big leak in the vacuum hose to my fuel pressure regulator. It's in a hidden postion and somewhat easy to overlook.

Bimmer805 · « **Reply #5 on:** January 04, 2011, 11:35:53 PM »

Quote from: colin86325;100103

I had a nice big leak in the vacuum hose to my fuel pressure regulator. It's in a hidden postion and somewhat easy to overlook.

thanks ill soon replace my hoses with silicone. its quite expensive but worth it

Bimmer805 · « **Reply #6 on:** January 04, 2011, 11:37:56 PM »

Quote from: DesktopDave;100073

That O2 might be your whole problem. They do wear out over time. You can get a cheap 4-wire Bosch from any early 90's Ford V8 IIRC, same part with a different connector. Splice that in with solder if possible...those heater wires pull a lot of current on startup.

You might have a lazy thermostat too. Your car should be pretty close to the halfway point most of the time.

Another cause of high NOx is leaks in the intake hoses. Spray them down with throttle body cleaner while the car is idling. If the engine changes it's idle speed when you spray a particular hose, you know you have a leak. Definitely check that fat hose under the throttle body. I've seen them crack clean in half.

oh ok thanks dave ill sure replace my hoses with silicone and o2 sensor but ill test it maybe this weekend ill keep u posted. thanks for your help again

DesktopDave · « **Reply #7 on:** January 05, 2011, 07:57:14 AM »

Iit's your dime, but I'm not sure I'd go for the silicon...wait until you have the problem figured out (before starting new ones). Rubber hose will work just fine as a temporary fix.

Bimmer805 · « **Reply #8 on:** January 05, 2011, 08:15:52 PM »

oh ok were can i get some good rubber hoses dave i want to replace all vacuum hoses

DesktopDave · « **Reply #9 on:** January 05, 2011, 08:31:13 PM »

Pelican Parts has metric vac line in many sizes. No doubt a BMW dealer could help too... You could also replace much of these lines with SAE vac line from any local auto parts store.