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Hi guys,

i have installed a 2.0 motronic engine into my e21 after many tries at fixing the solex failed. and it starts, idles and runs great. but the exhaust does give off some smoke when high reving and there are slight traces of fuel smell. when installing the engine i deleted the o2 sensor. could this be the reason? what else could be causing this smokey exhaust at high revs?

i read up online that without the 02 sensor the engine runs rich. what other downsides is there to not running the 02 sensor?

So you have black smoke? As that's the sign of over fueling.

If you remove the O2 sensor the Motronic will think it broke (no signal) so to prevent lean running conditions I believe it's making the mixture richer. What you can try is to fit a non-cat Motronic unit or have yours reprogrammed. With a MoDiC or DIS system you can easily set the O2 sensor function to 'no' and there must be some aftermarket software that's able to do that as well.

Thanks Jeroen!

whoa.. into the world of programming i must go..
but besides the rich mixture, what other downsides are there to deleting the o2 sensor? i am actually planning to install the o2 sensor but i can only do this way much later coz of time constraints currently. just wondering till i finally get around to doing it would i be damaging anything else because of this?

Fitting it isn't that difficult, there are special nuts you can weld onto the exhaust manifold. Together wit drilling a hole that's all that's required, in many cases that can be done without taking things apart as long as it doesn't stick out towards the bottom of course.

More important than a rich mixture, the O2 sensor also helps preventing much more harmful lean running conditions (potential huge engine damage) and helps adjusting the mixture to what is required improving fuel efficiency and engine performance.

thanks Jeroen,
think i will just go about the easy root and reinstall the thing ASAP.