Hi all, I have a 90' 740 B230F in Australia.

Problem 1 - Cold start problems. It starts on a cold morning but runs extremely rough, like its only running on 2 - 3 cylinders, and if you depress the accelerator it will stall and will not restart until you dry the spark plugs. If you let in run rough for a minute or 2, the car runs ok and smoothens out.

Problem 2 - Blows black smoke, when accelerating hard, and you can faintly see it when idling, poor fuel consumption, unresponsive when you touch the accelerator. All this above applies to problem 1.


Now I also have a 93' 940 B230F in perfect working order, and I swapped, plugs, ht leads, o2 sensor, amm, coolant temp sensor, fpr and this made no difference whatsoever.

So I put the ecu from the 9 into the 7 as they are both Bosch 935 units and now the cold start problem has gone away, idles perfectly but still black smoke, and a fuelly smell from the 740.

What is wrong with the Ecu, and why am I still blowing black smoke.



Any ideas?

Steven,

I am going through something very much the same as you and you have gotten good advice so far. There is also a lot of great stuff in the FAQs. I have done all that as well. Now I am into the wiring and I am hoping this will solve it since I have discovered a lot of bad insulation in the wiring harness. See my post of a few minutes ago. Ovlov87 300,000 miles

This could easily (probably) be the O2 sensor! Is the cat getting overheated?

a weak coil will cause black smoke on accel. low spark looks/acts like too much fuel. good luck, chuck.

The engione may have two temp sensors. One for the gauge and another for the ECU. Did you change both?

Check for a damaged fuel pressure regulator. It may be passing gas into the vacuum line.

Already swapped from 940, still the same

compression test, then fuel pressure test, then injector check/clean IMO