88 240 DL fails NOX emission testing

Ernie Ware · Post by **Ernie Ware** » 01 Oct 2002, 19:54

I have a 88 240 DL B230F, non-EGR, which is failing emission testing in
Rhode Island. The spark plugs, cap, rotor and catalytic converter (Bosal
099-937) are about 2 months old.

My initial emissions readings (in GPM) were HC =0.45, CO=0.02, NOX = 10.53. I was told the Catalytic converter was bad. This determination was made by a temperature test indicating the converter was not getting hot enough.

I checked the components I could, Temp sender, vacuum leaks, timing,ect. and found the O2 sensor was bad and replaced it (Bosch 224850 13006).

The vehicle was re-inspected and again failed NOX emissions; (in GPM) are HC =0.65, CO=1.13, NOX = 8.45 (NOX limit is 3.25 GPM)

Is it possible that I have a new catalytic converter that is bad?
Do I have another problem?
Can a NOX limit of 3.25 be achieved in a Non-EGR vehicle?

Anyone have any ideas or suggestions????

Thank You

760ti · Post by **760ti** » 03 Oct 2002, 19:03

High NOX are product of high cumbustion temps, caused by a couple things. Vacuum leaks, causing a lean mixture drive it up. You changed the O2 sensor, which richened the mixture (CO went from .02 to 1.13,). Still passed, and brought down NOx by 20%. So maybe check the mixture. It may still be a little lean. What's the upper limit for your CO emissions? Also check heater hose (metallic hose from the exhaust to the airbox). If the valve in the airbox is stuck open, it's sucking extra hot air off the exhaust and may be causing problems. As a last resort, retard the timing a few extra degrees. Advanced ignition causes high temps, and if you're engine has carbon on the pistons, your compression ratio is (a little) higher than normal, so you may have to retard the timing a little extra to compensate.

Ernie Ware · Post by **Ernie Ware** » 05 Oct 2002, 19:09

I'm getting 17-19 Inches of Vacuum depending on where I check. Did not think there was a valve on the heater hose so I will look at that. I plan on using a can of the upper end cleaner to remove the carbon in the cyclinders before I go for a retest.

RI emission limits are:

HC 2.25 GPM
CO 23.74 GPM
NOX 3.25 GPM

I agree with the lean aspect of the problem. Seems with a upper limit of 23.74, and a reading of 1.13, I have room to increase the mixture.

Thanks for your help.

kabohm · Post by **kabohm** » 09 Oct 2002, 19:03

To pass emissions tests in Germany the dealerships run the B230F motor for 2-3 minites at 3000 rpm because it does not pass when at idel speed!

By the way, how far can you drive at idle speed. makes no sense to test at idle speed.

Karl

Ian · Post by **Ian** » 12 Oct 2002, 12:26

I have a solution! ! !
I had one of these fail NOX this week.
After replacing the things you replaced also, I found the culprit.
The air intake hose had a hole rubbed through it after the mass air flow sensor.
It is located between the mass air flow sensor and the throttle plate.
This made the info from the MAF incorrect, causing a very lean mixture. Also check base ignition timing, should be 12 degrees BTDC.
I will check back to see if you are successful