348 help my 348 breaking up under 4k rpm

Any CEL or slow down lights? Any popping or backfires? Few other items that can contribute/cause:
-Clean MAFS and reset resistance to 383
-Intake cam sensor or connection
-The O2 sensors or connections
-Check your vacuum tubes see if any are loose or cracked.
-Crank position sensors.
-Water temp sending unit or connection.

 

Is this happening on one bank or both? The 348 basically has relatively independent electronics and fuel systems for each bank.

Re checking crank sensors; if it’s only happening on one bank swap them over and see what happens. If it’s on both banks just buy new ones, they are not expensive. Remember to check the gap.

 

Do you have something to check your exhaust manifold temperatures to see if you have one side hotter than the other? e.g. Infra red heat gun (with a suitable range). Since your car is not throwing up a CEL, the problem is difficult to isolate to one side of the engine.

The pumps are electric and not reliant on engine speed. You would assume if they are putting out enough fuel at 4000rpm they should be providing fuel for idle. However, I'm not sure of the symptoms of a faulty fuel regulator.

As the other folks say, it may be a timing/ignition issue. It could be the sensors, but since they aren't broken enough to generate a CEL, they may simply be out of adjustment. There is a crank sensor on each bank, so a faulty sensor should only affect one side. If it's on both sides, it could be a cam sensor (there is only one cam sensor for both banks).

Is your car a 2.5 or 2.7?

 

Do the CELs light up with ignition switched on before starting.? This confirms if the bulbs are fitted. Just a thought as many have been removed..

 

Yes good call there may be a cel. Check that first because if there is actually a cel after you swap the bulbs pull the code that will help.
As mentioned get a heat gun at home depot and check engine temps on both sides and isolate that.
There are threads out here for cam sensor replacement search for them.
Check the MAF resistance also it may be rich which may cause stumble. I'd pull them, clean them with MAF spray then reinstall and reset for good measure. Make sure that is right to begin with and its just easy labor. https://www.ferrarichat.com/forum/threads/348-maf-adjustment.167575/

 

Make sure the orientation of the MAFs is correct (with the arrow pointing in the right direction)

 

I'm going to make a guess, assuming both crank sensor magnets are working properly, ie: no frayed wiring down at the connectors/holder mount down by front pulley. Replace your ignition modules just below the coils. The originals are Bosch, but you can buy a cheaper module (Transpo BM325) for little $$. I had a similar problem as you, tried coils, nope.... bought 2 ign modules replaced the driver's side and voila, no more rich feeling, popping, misfire... Now, not sure how the Transpo units will work out long term, but they were available same day, and cheap! good luck.... And I thank this forum for someone else documenting this years ago, with the same symptoms. Be sure to use the given paste, or the new module will cook itself shortly.

 

If you read the diagnostic codes do it with the engine running or you will probably get false crank sensor codes. Possibly some other stuff too. Mafs maybe. Read whats there then clear them out. Run the engine until the fault occurs and read again to confirm. You may learn something from it.

 

id also check fuel presure on each bank, harbour freight sells those laser thermometers cheap, theyre great for checking temps all over the engine of the exhaust manifolds at the cylinder to verify theyre all firing.

 

If you're shopping on eBay for laser thermometers, make sure they have a suitable temperature range. Some don't go as high as others.

 

And most importantly, post what you found that fixed it.

 

also pull all codes out of the Motronic?

 

For what it's worth, both Motronics did not post any codes for my misfire/burping that the replaced ignition modules fixed.... therein the PITA!