87 325is Motronic 1.1/OBD questions.

[LBC28730]

Hello everyone.

I believe I know the answers here but would like to confirm as well as entertain other possibilities I haven't considered.

As stated, 1987 325is/M20/Motronic 1.1/everything stock.

I started noticing the CEL flashing just barely, a few weeks ago.
It was so fast that I wasn't even sure if I was imagining it, until I happened to be looking right at it one day.

Fuel pump and filter are OE relacements within the past year.
I always use premium, ethanol free Fuel from the same source.

Initially I noticed it when I was idling and engine up to temp, such idling at a traffic light.
it also seemed to be more pronounced when ambient temp was roughly +/=17c.

This lead me to believe it was something to do with the MAF or IAC.

Both appear to be functioning properly but of course with intermittent faults it's hard to nail down.

It's my understanding that the Motronic 1.1 does not store fault codes like the later OBD2 ECUs.

It is also my understanding that CEL is only associated with emmissions related factors but I can't find that information in the Bentley off-hand to confirm.

I wonder if the best course of action would be to watch the live data from the 21pin>INPA and see if I can determine what's happening when the CEL flashes?


I greatly appreciate any input, thanks.

[LBC28730]

Seems that ultimately, it would be the best idea to just upgrade to the 173 Grey label Motronic 1.3 and have the greater diagnostic capabilities in the future.

[moatilliatta]

Probably 02 sensor. Check power, replace relay, and sensor.

[LBC28730]

Probably 02 sensor. Check power, replace relay, and sensor.

Interesting. I'll take that into account, thanks!

It's certainly gotten more prominent.
I will test those parameters tomorrow.
I also found a good Motronic 1.3 so I'm going to do that, too, just to have that capacity in the future.

I'll update when I find the issue, hopefully assist someone else down the road.

[LBC28730]

It was the <1yr old fuel pump.

But, I have moronic 1.3, now, so it will be easier to diagnose next time.
Although the pump is under warranty, I'll probably exchange for new one and keep it, and go for single pump conversion on this car.