adallak Posted October 13, 2007 Report Share Posted October 13, 2007 I have been noticing for a while a strange noise when I start my 4. 9. It sounds like an explosion under the hood. What it could be? The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
Ranger Posted October 13, 2007 Report Share Posted October 13, 2007 Backfire? Link to comment Share on other sites More sharing options...
adallak Posted October 14, 2007 Author Report Share Posted October 14, 2007 Backfire? Sounds like... Is it going to get worse? Who are the culprits? The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
Bruce Nunnally Posted October 14, 2007 Report Share Posted October 14, 2007 With the northstar a backfire is often the sign of a failing fuel pressure regulator; perhaps the 4.9L has similar symptoms. The backfire itself can be very bad for the intake, and should be avoided. Long term I would say yes it will get worse until you diagnose and repair. Bruce 2023 Cadillac CT4-V Blackwing Follow me on: Twitter Instagram Youtube Link to comment Share on other sites More sharing options...
Ranger Posted October 14, 2007 Report Share Posted October 14, 2007 Yeah, I'd suspect a FPR leaking raw fuel into the manifold after shut down. Link to comment Share on other sites More sharing options...
adallak Posted October 14, 2007 Author Report Share Posted October 14, 2007 Thanks Bruce and Ranger, will check the FPR ASAP. I do check it from time to time, but probably need a closer look. Th ebackfire actually might be the reason the manifold developed a crack. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
WarrenJ Posted October 14, 2007 Report Share Posted October 14, 2007 The Northstar intake manifold has a handy little relief valve (or "door") that opens in the event of a backfire, thus saving your manifold from becoming plastic shrapnel. Surely the 4.9 has this as well? Anyone? Pardon the ignorance, but I never owned a 4.9L. Regards, Warren There is no means of avoiding the final collapse of a boom brought about by credit expansion. The alternative is only whether the crisis should come sooner as the result of a voluntary abandonment of further credit expansion, or later as a final and total catastrophe of the currency system involved. - Ludwig von Mises Link to comment Share on other sites More sharing options...
adallak Posted October 14, 2007 Author Report Share Posted October 14, 2007 The Northstar intake manifold has a handy little relief valve (or "door") that opens in the event of a backfire, thus saving your manifold from becoming plastic shrapnel. Surely the 4.9 has this as well? Anyone? Pardon the ignorance, but I never owned a 4.9L. Regards, Warren Thanks Warren. I guess a leaky injector can cause that too. I checked them recently and all the resistances were within specs though. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
Ranger Posted October 14, 2007 Report Share Posted October 14, 2007 I don't think that the 4.9 has a pressure relief valve. It is a cast iron manifold with the TB sitting on top like a conventional carburetor as I recall. Link to comment Share on other sites More sharing options...
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