85 735i Failed State Inspection High Nox

I have a 85 735i that I recently did a head job on. The car has been sitting for a while. I have replaced some of the injectors that were leaknig and the cold start valve and the fuel pressure regulator. Cats are lees than a year old. Replaced idle air solenoid a year ago. Cars runs and performs okay. Went to get it inspected and it failed for High Nox.

Readings are below. What can I do the get the Nox down ? I have not had the Air/Fuel ratio checked at the exhaust mainifold after the head job. Could this help ?

Pollutant Reading Standard

HC 110 152
Co% .70 .97
CO2% 13.4 N/A
Nox 1582 1082 FAIL
Dilution 14.1 >6

I had a similar problem with my 79/733i and after fixing the leaks at the intake manifold the mech. retarded the timing, did a pre-test,I didn't have any power but got to the smog place and it passed. Went back and readjusted the timing. Also I know that I do need a new thermal reactor/3way cat. Hope this helps with some ideas...

Thanks for the reply. Unfortunatley on the 85 the ECM controls the timing. The only manual adjustment that I am aware of is the air fuel ratio.

I may have to take it to the shop simply because I don't have any way to measure the air /fuel ratio.

kloller

is the 02 sensor working properly?

Yea I think the O2 is fine. I learned from the Texas emissions web that a lean air/fuel ratio can cause this problem. I had trouble with the car and did a head job prior to this inspection. Before the head job I had it in the shop and I think they leaned it out to compensate for a leaky cold start valve and two leaky injectors that I found during the head rebuild. I am going to take it somwhere and get the air/fuel reset once I get thru the tranny problem I posted in another thread.

I have been told that typically it is the CAT or the EGR valve that causes the high Nox. O2 and CATs are relatively new. Bigger problem right now is the damn failed transmission. I think the inspector held the RPM's up on it before he ran the dyno but cannot prove it. I knew should have watched them run the test.

Well, I had that problem and the mechanic cleaned the top-end first with negative results ($100) before selling me a new catalytic converter ($900) go figure. I think he new it was that all along.

"If your 85 735i failed (VA-USA) and the engine is well maintained there is a 90% chance that you need to replace your catalytic converter, it's too old.

you can also change the settings in the ECU . there is a seven position switch in the ECU , the setting are as follows:

1. Stock

2. 3% increase in injector open time, no timing change

3. 3% decrease in injector open time, no timing change

4. 6% increase in injector open time, no timing change

5. 3% increase in injector open time, 2.78deg retard

6. 3% decrease in injector open time, 2.78deg retard

7. 6% increase in injector open time, 2.78deg retard



these adjustments were to allow for different climate and poor fuel quality issues. You may also want to check the barometric pressure sensor on the fire wall next to the ECU relay.



i hope this helps !!!


mark

you can also change the settings in the ECU . there is a seven position switch in the ECU , the setting are as follows:

1. Stock

2. 3% increase in injector open time, no timing change

3. 3% decrease in injector open time, no timing change

4. 6% increase in injector open time, no timing change

5. 3% increase in injector open time, 2.78deg retard

6. 3% decrease in injector open time, 2.78deg retard

7. 6% increase in injector open time, 2.78deg retard



these adjustments were to allow for different climate and poor fuel quality issues. You may also want to check the barometric pressure sensor on the fire wall next to the ECU relay.



i hope this helps !!!


mark


Hi Mark, I understand this post is very old, but I am faced with a similar problem. I failed the test. Everything passed with flying colors except the idle test.
It's now geting cold here in PA, and the car doesn't want to start on cold days, seems the battery drains out or something. All summer never had an issue, but now that its cold, it's in trouble.

New battery, new plugs, wires and and I'm wondering if your post here might help me.

Thanks in advance

Here is a website for M30 no start problems:

http://home.bellsouth.net/p/s/community.dll?ep=16&ext=1&groupid=160912&ck=

For electrical drain, get test light, pull fuses from fuseblock. Use test light across each circuit. When you find a circuit that lights the test light, you have found the troubleshooting path. Good luck and check back to let us know what you found.

My 1986 735 also failed with 2 year old. Cat converter and passed after replacement.