348 resetting of ECUs

As I understand it, you simply have to make sure that ALL of the electrical power is disconnected, by whatever means you wish. You don't want to leave anything connected that may provide "memory" power to any circuit. Since my 348 has a rear battery (no disconnect knob), I don't really know if turning the knob shuts off ALL of the power on a front battery car. But disconnecting a battery terminal (either one) is certain to do it.

 

If you have the knob/turn switch that will disconnect power to clear the ECUs, it shuts down the entire car. Regards, Vern

 

By resetting the ECU, what does it do to the car?

Will it in any way affect the performance of the car?

Is there a certain way you have to run the car after you reset the ECU?

 

It erases adaptive memory.

It will not correct a thing if the car is in correct running order.

The Motronic 2.7 which all but the very early 348's and some later Ferrari's have is the last system used by Ferrari for which Bosch has shared that information.

In those cars it should be started cold and allowed to idle undestrurbed with everything off for 15 minutes.

During that time all of the required data will have been reestablished.

What will not have been reestablished however is the data base of information that is recorded over time that is beneficial to the cars operation.

It is best to leave it alone unless there is a problem that requires a relearn after the repair.

 

Do you experience this slight "miss" at wide open throttle or only at partial throttle?

I ask because the adaptive air/fuel data in the Motronic 2.7 ECU's only applies to the various partial throttle A/F maps, so far as I've been able to ascertain (i.e. resetting the ecu's won't have any effect on full throttle conditions).

So it's important to know if your problem occurs at full throttle or not.

 

I'd try to narrow the problem down just a bit. **IF** you get this behavior at idle and 4k rpms when the engine is cold, that will mean something different than when hot.

This is because the ECUs ignore the O2 sensors under two conditions: when cold and when at full throttle.

So if the problem doesn't happen when the engine is cold, that would hint at this being an O2 sensor issue (common for 348's). Old O2 sensors will often start to cause a "surging" or lagging when you are trying to maintain a constant speed.

But if this idle and 4k rpms problem happens all of the time, engine hot and engine cold, then I'd start looking at spark plugs and spark plug wires first.

 

So if the car response does not feel right/efficient, do you turn off the battery knob and later turn it on and let it idle for 15min?

If so, how long must the battery be turned off?

 

Here you go: http://webpages.charter.net/aircover/348/1994Ferrari348Spider.html#ECUs

Scroll down to the "reinitializing A/F ECU" section.

 

I doubt your missing problem would be the O2 sensors. First the CELs would come on to show there was a problem with their(O2) operation. Second(even if they were acting up) the chances of them causing a miss are nil they're only effect on motronic 2.7s is to fine tune the A/F ratio to keep it at 14.7:1 at part/steady state throttle and idle. The fuel map that is set/programed for that ECU and what the airflow meters information is is the main source for the mixture. I have unplugged the O2 sensors on 2.7 motronics before and if anything the engine runs a little better(except that the CELs come on) and I never incountered a miss. I would have to go along with starting with the plugs, wires/ignition route first. Regards, Vern

 

Vern is correct that you will get a check engine light if you disconnect an O2 sensor, but...O2 sensors do age and go bad over time **without** triggering CEL's. This is a well-documented 348 problem identifiable by surging or lagging when trying to maintain a street cruising speed.

As for the fuel maps inside the ECUs being the primary source...I'm unconvinced. For various partial throttle conditions, the Motronic 2.7 system looks first at the stored fuel map or at the adaptive (learned) data based upon how close the fuel maps are getting the correct A/F ratio as told by each O2 sensor.

Vern is correct again, however, that if the O2 sensor is bad or disconnected that the Motronic 2.7 will seemlessly and flawlessly revert back to the stored Fuel Maps.

 

Not going to waste my time argueing I'll stand by what I said above it's not the O2 sensor that's the problem.

 

Dave, How old are the plug wires on your car? That would be where I would start. Maybe check the resistance in each, that doesn't always show a problem but I would check that out. You didn't say if you were ever getting a CEL coming on, have you? You should be fine with cleaning the inside of that plug wire just make sure you let it dry before putting it back. Regards, Vern

 

Try having a look at the condition of the crank postion sensors. The pictures in this thread http://ferrarichat.com/forum/showthread.php?t=96065 show what they look like, and where they are. Also check the condition of the connections to your mass air flow sensors.

 

Out of what you listed above I'd question the wires as well as the .025" gap. If that's what you were sold, then you may have incorrect spark plugs.

The 348 should have a .028" gap on each spark plug. What heat range are your NGK's?

 

Dave I'm still leanin' on those plug wires. Do you have the old wires? Just a thought on reinstalling to see if they give in different reaction. Are your CEL lights working? do they lite up at start up? Have you checked ECUs for stored codes? I have had codes stored on occation and no CEL or maybe I didn't see them flash on the off. You could try unplugging the O2 sensors after car is warmed up to see if things change the engine will run slightly richer(CELs will come on but won't hurt anything). I'm kinda grabbing for straws here but just trying to help. Regards, Vern

 

That lifetime warranty is good to know. Thanks.

 

Thanks for the update, glad to hear the problem seems to be solved.