Ferrari 355 Check Engine 5-8

Rf355AU · Oct 29, 2022

ernie said: ↑

A few other things to consider.

The 1995 cars are now almost 3 decades old. You may need new EPROMs inside the Motronic 2.7 units. Those get old and overtime don’t run as efficiently as they did when they were new.
https://www.ferrarichat.com/forum/threads/348-ecu-removal-chip-removal.351819/

You also may want to look at the condition of the female connector pins on the T55 connectors. If they have the old the junior timer pins you will want to replace them for a set of Junior Timer Power pins. The Power pins are reinforced and clamp much better. They do not have the tendency to separate overtime.
https://www.ferrarichat.com/forum/threads/348-motronic-2-7-connector-harness-repin.444155/#post143057320

The links I posted are for a 348. However, as I said earlier, the F355 2.7 Motronic should be very close to the same procedure.

Another thing to consider are the operating temperatures of the car. This thread by gothspeed explains why. https://www.ferrarichat.com/forum/threads/355-owners-only-more-data-samples-needed-anonymous-poll.377706/page-2#post-141700601
In a nutshell there are three fuel maps. The first map is initial start up (rich to get the cats to light off faster), the second map is intermediate running (semi rich), and the final map is full operating temperature final fuel ratio map. So if your car is not running at the proper temperatures it will screw that up and can cause a lambda issue. The main thing to check for is your thermostat in this case.

Finally I found the majority of the stuff using the search function, and the DIY sticky in the 348/355 section.
Click to expand...

Thanks Ernie. Very helpful for a noob like me.

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