456 issues

Hmmmm what work have you had done thus far ?
Anything recent ?

My head goes to bad injector(s) or disintegrating rubber bits.
Does it run fine when pushed to start ?

 

CEL? One bank cold?

 

“20% of the time it runs perfect out of nowhere and gives huge amounts of torque and can break the traction at the wheels!”

What are the exact conditions under which this occurs ? Is it when the car starts under certain conditions or does this occur while driving, etc. That tell you something

 

At this point, it literally could be anything. Do you have a US car? What version of the 456 do you have?

When you turn on the key, does your Check Engine Light illuminate (as part of the startup sequence)? Does it extinguish if you get it to start (when it's not running properly) or does it remain or come back on. Similarly, does the SLOW DOWN light illuminate? Do you have anything to check the temperature of the left and right exhaust manifolds?

 

Sound fuel related and if you haven’t done the fuel pump upgrade, and/or changed filters, and/or cleaned your injectors that may help.
I can’t see how your timing would have just gone so far out…but fuel issues on these cars is a known and basically fixable thing
Good luck - let us know what you find out!

 

I don't know if the early 456's shut down a bank if they are getting false high temp signals from faulty Cat/thermocouple ECUs or thermocouples. Or if the shutdown is immediate (from engine start).

Generally, if you think your engine is running on one bank, you can always disconnect various engine items to see if the engine worsens or completely dies. e.g. If a fuel pump is failing, pull one of the fuel pump relays to see if the engine stops completely. If no change, pull the other fuel pump relay. Pulling the plug on a MAF may make the engine run worse, or better. If a MAF is faulty and you pull the plug, the respective engine ECU switches to other sensors to compensate (although the car may struggle for a few moments during the sensor switchover period).

 

Your owner's handbook should show you the location of the relays in the passenger footwell.

If not, I would download a workshop manual for the 456. Since I don' t know which version of the 456 you have, I'll let you Google for that.

2.7 engine management system? 5.2? M? GT? GTA?

 

Old 2.7 GT relay panel

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Start by removing any floor mats that may be pressing on the throttle cable and inspect said cable to make sure no fraying/damage