355 BACKFIRES MISTERY SOLVED

Like some might have noticed, I have been posting threads for almost a year on backfires ON 355´s with no precise answers about the cause. Many pointed air leaks, too rich on the mix, manifolds cracked (most popular) and although I really appreciate everyone´s input, I have to give the credit to Daniel at Ricambi and the guys at Weber Automundo in Monterrey, Mexico.

I had made my mind up about getting new manifolds (which I will but not right now) with new cats (which I AM getting -Hyperflows) and called Daniel at Ricambi, after doing some shopping arround. The reason I want to give him credit is because instead of jumping into selling me manifolds right away, he was genuinely interested in getting the facts and symptoms over the phone. He then suggested that backfires could be related to the bypass valve or vaccum guides, not precisely manifolds cracking. That although 355´s in fact go bad on headers, the symtoms are more "tapping noises" than back fires.

I took the car to Weber Automundo where they noticed the valve hose was worn out and the vaccum guide almost broken. They had to take the valve appart and revise it. The mechanic sucked on the pipe to see if it wasn´t getting stuck, and found out it was ok. He then put a new guide (it goes from the bypass valve to a selenoid connector on the passanger side) and a temporary hose to see if the backfires stopped. We left the car iddling for an hour until it got really warm and then drove it with "enjundia" (that´s spanish slang for "intense"). The result: backfires are gone!

Hope this thread helps other 355 owner´s when dealing with backfires that only occur on decelleration and when car gets hot.

PD. The hose has to be high temeperature resistant, others won´t last much (days maybe) and it can make one think there is another problem.

Good luck.
Feliciano
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Thanks for noticing, that was just a rag the machanic put there while taking the valve out.

Thanks

 

I will look into that. My car is a 1995 F355 Spider (22K miles).

 

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