F40 misfiring after 4500 rpm's

Fuse box ? I had to rebuild mine, they were only built to last 10 years or so

 

I haven't owned an F40 before, but it sounds like an ignition timing issue.

Is the advance too much when it misfires and not enough when you have lower power? Just a guess.

Regards,
Richard

 

F40s are very sensetive to fuel pressure. The engine ECU will not allow the engine to run above certain RPMs if there is not enough fuel. At idle and low RPMs the engine has adequate pressure but not at 4500 rpms. You need a good fuel pressure gauge to test both pumps, left and right. The pumps must achieve pressure and hold it with the ignition swith on the turned off. I am not sure of the pressure spec off the top of my head. Some of the additives in todays gasoline can damage parts of the pump and weaken their capacity.

 

Good advise here...

Also note that the injectors are shut off at manifold pressure above 21-22 psi (1.45 bar) gauge (2.45 bar absolute). Normal manifold pressure (at least for a US car) is 1.1 bar. And remember, cold winter air (more dense) may cause overboost on a car that will not show this problem in the summer.

Could be:
ingition
fuel pressure
injection
electrical (ground, voltage)

Best regards,

Rob Schermerhorn

 

Spark plug wires?????

 

I agree with this; it sounds like a bad coil wire or bad coil wire connection within the cap.

 

Check the fuel pressure, but fuel pumps are in the fuel tanks (1 per side), so pretty expensive to repair. Exclude simpler things first.... previous owner had a similar problem with my car and had one of the pumps exchanged

Good luck. Let us know what the issue was when you resolve it.

Simon

 

Have you checked the power supply to the fuel pumps? They may test as good, but may have intermittent power issues from the harness. Could be one of the coils though, but i when i've seen them go bad, the car has issues when cold and runs fine once it warms up.

 

Do not diagnose without the proper tools. Put the car on a scopemeter to find the missing cylinder. Wires can look good and pass under simple tests and fool you. If you find a miss in cy 6 then swap wire with cly 7 to see if you can move the miss. If you can your wire is bad regardless of what your ohm meter tells you. IMO fuel pressure is the first step at idle and under max load. It should have a hold time but that is not critical except when hot for hot restarts. Then even if pressure is correct you have to check the flow volume. However, knowing Ferrari your problem is likely electrical. It can be anything from a bad wire to a bad TDC sensor etc.. depending on how the F40 works i.e. KE-jet, motronic etc....

 

Best advice in the thread so far. Follow it...oh and its a motronic system in the F-40..no blasted fuel distributors to worry about...

 

This may be a redundant question but, when was the last time you changed the fuel filters?

The reason I ask is because Roland had a bad misfire with his F40. The fuel filter wasn't the problem though. What it turned out to be was a bad fuel line. The wrong type was used and the rubber got deteriorated. The rubber then settled in the gas tank. So when he first started the car is ran great. But as he drove it more, the rubber was getting sucked up, and the car would misfire. He would shut it off and the rubber would settle, it would run fine after it had sat for a while, then start misfiring again as he drove it. So I suggest the fuel filters to see if you have any trace of deteriorated rubber in it. Roland finally found the problem by draining the tank, removing, and inspecting it when they found the rubber inside. He changed the fuel lines and the problem was solved.

 

Thanks for the vote of confidence. Makes my head swell coming from a real technician like yourself.

 

Oh great that's all we need. Fatbillybob with a fatter head. LOL

 

It's Weber-Marelli alpha-n injection/ingnition, not Bosch. No mass airflow sensor, no airflow plate. Alpha meaning throttle position, and 'n' meaning rpm.

Injection and ignition maps are selected by those primary inputs, of course there's temperature sensors for coolant and air, manifold pressure....

Best regards,

Rob Schermerhorn

 

I have seen it on more than one occasion. The last time the F40 owner filled up with 104 Octane fuel before storing the car for the winter. The gas ate away at the rubber seals in the pump. The pump operated but with diminished capacity. The F40 ECUs won't let the car run lean. It starts to drop cylinders to tell you something is wrong and prevent a lean burn condition. I would be interested to know if anyone has come up with higher capacity fuel pump which is a direct replacement?

 

An wideband o2 display would be an good idea on an turbo boostet car. To see those problems immediately. Because of those problems i saw many engines with damaged pistons on our shop.

 

Glad to hear you got it sorted out. Thanks for the update.

 

Will all due repect this is not true. The lambda sensor as OE is only there for emissions compliance and the ecu runs closed-loop only when not at full throttle. The only fuel cut-off occurs at either redline or overboost (about 1.45bar).

I've not found the OE fuel pump a limiting factor on US in-tank pumps to 650 bhp.

That said it would not be difficult to adapt a larger volume pump.

Best regards,

Rob

 

whats the black stuff blocking the filters...

looks a bit like rubber fuel cell disintigrating......