[kreine]

All I have a car as stated in the subject that won't pass emissions. Here are the test results:

HC GPM Reading: 2.8121 limit is 1.500 (fail) CO GPM Reading: 57.8164 limit is 15.000 (fail)
CO2 GPM Reading: 347.2868
NOx GPM Reading: 0.0567

Catalytic converter--Pass
Fuel Filter Restrictor--N/A
Air Injection System: N/A
Oxygen Sensor: Pass
Check Engine Light--Fail

High HC reading:
High HC Readings are a result of unburned or partially burned fuel

High CO readings occur when the air/fuel mixture is too rich

With that said ... it seems to me that the thing is getting too much fuel. When I changed the plugs, all of them appeared to have been running rich. There as also a slight burble in the idle once the car was warm. So I replaced all of the Vacume lines and changed the fuel pressure regulator as the car has 165K miles. Took it in and had it re-tested and the HC and CO readings actually got worse and read what you see posted above.

Now I'm just a shade tree mechanic but I have owned several older BMWs int he past and here are my general assumptions:
1. If it were an injector ... only one cylinder would have apeared to be rich when I swapped out the plugs. All 6 had dark, shiney black deposits as if all 6 cylinders were running too rich.
2. The fuel pressure and vacume hose replacement cleared the erattic idle but made the emissions worse.
3. Since this is the M50 motor the coil packs are on each cylinder and there must be some sensor bad that is causing the ECU to deliver too much gas. Guess I'm trying to say ... it ain't the distributor cause there isn't one.
4. If it was the TPS the idle would hunt ... the idle is steady so TPS is probably set right.
5. If it was the O2 or cat, the numbers might be slightly over by not by the percentages shown in the test.

Can anyone give me an idea of what to test first and maybe provide a diagnostic decision tree based on experience? I have a bently and when I get back to Denver this weekend I'll start going through that if no one has a better idea. Guess I was just wondering if there was a thermo time swicth or something like the older BMWs had that might be an immediate suspect?

 

[ThoreauHD]

Well, start small. Your car apparently knows somethings wrong if 'check engine light' fail is accurate.

http://www.bmw4life.com/stompTest.htm

Do a stomp test and get the codes before eye balling it. Could be anything from a dying O2 sensor, to spark plugs, to MAF, to ICV, to vacuum leak, etc. I'm assuming you've done a tune-up somewhat recently(oil/oil filter/air filter, etc).

If it's running rich on all plugs, then that's a good thing. It's consistent and would point to the O2 sensor. But get the codes and verify. Don't trust. Let us know what you find and we can work from there.

 

[luckydog]

I think onbord diagnostic or Stomp test was Incorporated in the DME in the later part of 92. Early 92 may not have the feature.With that high of reading i would do a full tune up ,air filter too . make sure you have both clamps on the 4" 90 degree intake boot. i would remove the oil filter + add 1 qt sea foam to oil,try not to over fill the oil level.Drive it fo 50 miles then change the oil and add new oil filter. Also try a different smog tech. I always use CRC bbe fore a smog test www.amazon.com/CRC-05063-Guaranteed...PUR8/ref=sr_1_1?ie=UTF8&qid=1320979275&sr=8-1 A member shared this link with us not long ago.http://www.smogtips.com/failed-high-hydrocarbons-lterHC.cfm

 

[kreine]

Problem Solved

So as it turns out the car does have a coolant temperature switch that sends feedback to the ECU. It is located under the intake manifold behind the oil filter. It was reading 2.8 ohms at normal operating temperature instead of the .27 - .40 ohms it should have reported. Needless to say the computer thought the car was cold and as a result it was running rich which caused it to fail the emissions.

As a FYI, the check engine light wasn't on and stomp test showed no problems and the car still failed emissions. Turns out the idiot at the emissions test center thought the Fog Light Indicator on the dash was the check engine light. I installed two new fog lights and cleared the display on the dash.

Anyway problem solved. Thank goodness for the Bentley Manual!

 

[Jeff Turcotte]

Quick question if any of you are still around. Does the temp sensor that failed here not run the temp gage? I have the same vehicle running rich but the temp gage is showing operation temp. If this is a second sensor, it may be my problem too. Thanks in advance for any help.

 

[oiphy]

Quick question if any of you are still around. Does the temp sensor that failed here not run the temp gage? I have the same vehicle running rich but the temp gage is showing operation temp. If this is a second sensor, it may be my problem too. Thanks in advance for any help.

Quick question if any of you are still around. Does the temp sensor that failed here not run the temp gage? I have the same vehicle running rich but the temp gage is showing operation temp. If this is a second sensor, it may be my problem too. Thanks in advance for any help.

different temp sensors for intake air and temp gauge. and one more for outside temp in the front bumper

 

[Jeff Turcotte]

Thanks. I realized when I checked later that the two coolant temp sensors are side by side—one for the gauge and one for the computer.