355 work well but not powerfull

Is your by-pass valve operatng correctly?

 

+1 bypass will lose discernable power....

 

Are any sensors still unplugged?


Your water temp sensors will influence performance at all levels.

Your O2 sensors will influence performance in mid-range rpms when the motor is warm.

 

+1 May want to first clean and lube all sensor connections......also make sure that they are all in good condition physically......under hood temps can make connectors and wiring brittle.

Have you done a recent compression/leak down test?

 

I agree with last post...intake valve guides are a NOTORIOUS F355 weak point...up to late 1998(?)
It is not if,
but when....

ONLY an accurate leakdown will tell the story there.

If you've got good cylinder chamber sealing, then the electrics can accurrately be whittled away...

If guides are required, you will likely need all valves if over 20,000 miles. certainly intakes-in my experience.(taper in stems)
Use only the silly expensive Ferrari "composite" replacement guides-look like, act like, taste like, smells like cast iron-but start out as some sort of powder and turns into the guides under huge temp and pressures of the manufacturing process...They told me it's some sort of composite(?)...it's not really important-it's just that they seem to last way longer than the "machine shop replacements."
Which, by the way, I've seen wear out in another 10-20,000 miles, on more than 3 different occassions.
Not a knock on the machine shops, just the materials used....this is a $20,000.00 job after all, who wants to do it again so soon just because the other guides were a couple of thousand cheaper!
Please, let us know of the outcome...

 

I doubt that this is his problem as it would not have come on all at once right after changing the wires. He more than likely has an electrical problem somewhere in a connection or wire. $20,000 to re an re the heads? Sounds like a lot to me.

 

Have you had it done? I've got a bill for $27K sitting around.
But the OP's problem must be something else if it happened suddenly. An bad electrical connectiong or faulty sensor could cause the engine to run with less power.

 

I donot need the valve guides replaced but I was quoted by my mechanic (ex ferrari dealer mechanic) $5500.00 for the complete valve guide job....., not 20g or 27 g.
You need to find a new mechanic.

Also not all 1995-1998 355's need valve guide replacement......in fact I know of at least 16 355's with some having in excess of 100,000 klm that are still on the stock valve guides and exhaust manifolds.

What usually cause a failure of either of the above items is another problem.....usually a failure of the exhaust bypass valve. It fails in the closed or partially closed position and at high revs causes an excessive heat backlash to the guides and exhaust manifolds.

It seems that a lot of people on the internet are 'creating' the valve guide failure myth. I'M NOT SAYING there are no failures but they are few and far between.

I went to my local ferrari dealer and asked them how many valve guide failures they had and they numbered less than 10 and ALL of them occured in the first couple of years ( from new).
If it has'nt happened in the last 12 years......don't worry about it.

But it is a good idea to replace your bypass valve with a challenge pipe so that you don't become a victim of these failures. And to boot the car sounds a little more aggresive.....very much like a tubi.

The bypass valve serves only two functions.....to allow the car to pass noise regulations AND to help the car in an emission test. The emission test is at lower rpm's where the bypass valve is closed and the exhaust is routed through the more stringent main cats.

The internet chat lines are a great resource but the myths that it can create are unreal. A lot of chatters are NON OWNERS (and never will be Ferrari owners), who suddenly became experts when typing on their laptops.

I also donot believe that this ferrari chatter has a valve guide issue.....it sounds like a bypass valve problem......wire it open temporarily and see if it addressed your power loss problems. Also failed cats can cause a power loss.....remove the cats and make sure the catalyst is still intact and not blocking the exhaust flow.

I had to vent.....let the flames begin.

p.s. I do own a 1995 355 and have NO issues except for regular maintenance .....on a 12 year old car.

 

But don't leave it this way. Otherwise valve guides are the least of your worries.

 

Exactly what problems are created by wiring open the bypass valve?

Again I have had NO bypass valve in my car since it was new and there are absolutely no negative side affects.
AND THE BYPASS CHALLENGE PIPE WAS INSTALLED BY MY LOCAL FERRARI DEALER. They have installed the bypass pipes on 355's from 1995-1999 years.
Also there are many 355 owners on this site who have stated they have wired open their bypass valves because they could not be bothered installing the challenge bypass pipe.

On a 1995 355 there will be no service engine light but on a 1996 and later car the service engine light will come on due to OBD2. Some owners just ignore the light (it does not affect the car at all) and others who are irritated by the light put some tape over it. I DONOT RECOMMEND TAPING OVER THE LIGHT because if a relivent service code lit up ...you would not know it.

Again I reiterate.....you must review all internet comments with a grain of salt.

I recommend all owners to take any information you obtain on the internet and speak with a real Ferrari dealer mechanic before you act on any of the recommendations.

 

you should check the vacuum reservoir cannister in the right hand rear corner behind the rear bumper. It's mounted on the same bracket as the air pump. I'd bet it's got a hole in it. Let us know what you discover...

Ciao, Bob.

 

Hi Nico
have you check you have not a wiring inversion between the the two electro-valves which are there:
- one for the command of a vacuum driven valve for air injection in the exhaust at cold start-up
- one for the command of the vacuum driven exhaust valve
Both are commanded by the engine ECU and have the same connector. Both are connected to the vacuum tank. Just a thought ....

 

I have had the challenge bypass pipe on for years on my 95 355B. I think everyone should be installing this part. Its only a $150 dollar item and can be changed easily.