my 740 ti with 150000kms, got more than double the allowed limit by ontario standards . at idle it pass with flying colors ,but at 1800rpm even the NO's where high just enougth to pass, i changed the o2 sensor, spark plugs .but did not change it all , i can see black smoke around the tail pipe , What shoud i do !!!!!TO ALL THE GURUS !!!!!
please HELP!!!!

a couple of other things to consider

1. wiring harness conditions to injectors, splicing rotting sections
2. rework all ground connections
3. at AMM you can turn screw 1/4 - 1/2 turn left to reduce emissions for test
(your choice to do this)
4. try bottle of guaranteed to pass additive, reduces all but HC emissions.

3 and 4 will help a borderline case,
1 affects HC a lot and I'm currently doing this job on a B230FT. First getting the valve clearances correct and rebuilding distributor. In this car the diagnosis indicated spurious voltages at the throttle switch, most likely from a failing wiring harness. Therefore the redo on the harness after baselining it to good mechanical condition.
HTH
Rk

1. wiring harness conditions to injectors, splicing rotting sections
How? What is the fault mode causing increased HC?

TIA

Dan

HC hi indicates incomplete combustion. I had a 740 that failed in similar manner and I think you are on the right track. Do the easy stuff first.

Check to see if the fuel pressure regulator is leaking. It is located at the front of the fuel rail on the dirvers side of the engine. There is a small vacuum hose connecting to the intake manifold. remove this vacuum hose and see if there is any gas in it. If so, the FPR must be replaced.

Clean or easier replace the flame trap ($2.00). I can't prove it, but think this was the most helpfull in getting the emissions down on my car.

Changing the oil will help some, but not likely 2X better.

Change the air filter if at all clogged/old ($5.00).

Check and adjust base Idle speed and CO as per FAQ -- May be controlled by the computer on 1990 model in which case disregard.

What is te condition of your ignition wires ($35.00), cap($20.00???) and rotor ($5.00).

What did the old plugs look like whe you removed them? Did you gap the new plugs to Spec (0.028" to 0.032")? They come out of the box much wider than this.

You should also make sure that the engine is fully up to operating temperature when you go in for the test. Drive around for 1/2 hour at least. Quenching of the flame at the cylinder walls is one of the main reasons that combustion is not more efficient in IC engines. Having said that, check to make sure the engine is coming up to temp. Thermostat not stuck open and coolant cap working properly.

One last question. Is the 1800 rpm a static or a dynomometer test? If static, there may be a risk of damage if you have the ZF transmission P-R-N-D-3-2-1). Check the 700/900 FAQ for details. 1800 rpm may be low enough to prevent serious damage -- I can't remember the details.

Dan