Slow acceleration F355 and not good sound from the exhaust

I think there is something wrong with the my car, I have 97/98 F355 with manual transmission. My car behaves very strangely when I have under 4000RPM. I get very little acceleration and the car sounds very quiet when I have the car under 4000RPM.. But over 4000RPM I get some sound from the exhaust (but still not as before). I feel that the car is a lot slower than before.

It is also hard to get it up in speed over 6000rpm, and I dont have any good sound like before when i achieves over 6000rpm.. the car will not go well as before.

what could it be? I have replaced all spark plugs, but it is exactly the same as before.

 

slow down, check engine lights ? do they even work?

 

I have not got any error message..

 

Check the cats. In my evo IX I had a plugged cat and I experienced this same thing, very slow revving, less sound, no way to boost beyond 0.4 bar... evos have nothing to do with ferraris but it could be a possibility.

 

I have no cats, I have Capristo decat and Capristo stage 2 exhaust system. maybe my exhaust system that is broken?

 

If no cats I would check that the maf is clean, and if it is... I would then take it to a specialist. Did you have a cambelt change recently? check that the cam belts are tight and in good condition.

 

all of the belts were replaced in 2007.. how do I clean the MAF???

 

With a no residue electrical contact cleaner spray. There are also maf cleaner sprays but I believe they are the same. Take the maf out and spray inside, you will see very thin wires, DON´T TOUCH THEM! Spray in the inside of the brownish circle piece in the picture. (the maf in the picture is not from a ferrari)

Also, you changed the belts in 2007... to 2011 its 4 years so you have to change the belts ASAP, check that the belts are not breaking apart or that they are not loose before starting the car again, they could have jumped a tooth and that´s why you could be experiencing those problems.
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where is the MAF on F355???

 

Center tube between the air filter and the air boxes above the throttle bodies.

The thing with the white dot on it.
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Baffle in exhaust broken loose? Buy a cheap engine stethescope or use a broomstick to listen.

 

I think you may still actually have the two main cats, and they have broken. Perhaps the Capristo decat was only the top (secondary) cats.

 

Lets not get ahead of ourselves.

Based on your description, my first thought would be to test fuel pressure with a trusted gauge. If your cats are out, you may have had programming done to circumvent the post cat O2 sensors; which isn't helping as far as diagnosis. I would start with that and move from there.

Certainly would not surprise me if your Mass Air is bad or some of the other suggestions such as a broken baffle in the exhaust, but before you start swapping parts I'd get a few things known good or bad before coughing up some cash for parts you don't need.

 

thanks for the quick response, I have cleaned the MAF, but still does not help