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Registered
Join Date: Apr 2007
Posts: 95
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Backfire on shifts. Didn't do that before? (3.2 '84)
I did a quick search on back fires. I think it happens during both up and down shifts. Definitely when shifting on extreme accelerations. Two main causes were popping up a lot:
1. running too rich 2. Exhaust / vacuum leaks Since it didn't do that before I assume running too rich is not an option. Furthermore, I think the exhaust sound isn't as 'dark' as before. What do you guys think? Is my assumption fair and if it is the exhaust or vacuum then how do I check that and repair it? ps.: This message also exist on the engine rebuild forum, but don't know how to remove. |
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07-28-2009, 08:51 AM
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Join Date: Oct 2002
Posts: 2,084
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Didn't do it before what?....did anything change?
Or it just started all of a sudden...with no changes to anything?
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Jeff |
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07-28-2009, 10:16 AM
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Registered
Join Date: Aug 2000
Location: Calabasas, California
Posts: 829
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I can add that on another car I was getting pops on upshifts and the exhaust seemed loud. I was dealing with the exhaust and a shop checked it out and said no leaks. Well, guess what completely failed yesterday? One of the exhaust gaskets. So, I guess sometimes confirming an exhaust leak is not so simple (at least for those that clearly useless).
I am going to replace it this weekend and see what it does for the pops and the sounds. YMMV. Good luck. |
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07-28-2009, 01:50 PM
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Monkey Butt Forespin
Join Date: Jul 2007
Location: Cumberland, RI
Posts: 474
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I have both.
 Running a Weltmeister chip, and also have the fuel switch set to +6% fuel. I make better power, but also more idle surging. I run copper gaskets, and a couple of weeks in spring, and a couple in fall, I remove my M&K muffler & put the dump tip on there. Much more noticeable with the dump tip than with the muffler, but the M&K still does it more than a stock setup. The coppers are nice so I can remove the premuffler during valve adjusts to make it easier to get in & out of there. You can use some Walker Acoustiseal on the gasket faces if you like, which helps to minimize gasket leaks, I've found. Check the hoses on the top end of the engine, and check the sides you can't see with a mirror too. If you can localize which side the pop is coming from, you'll be ahead of the game.
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Fred Hurder Jr For Tech Questions: '84 911 Carrera Cabriolet (US) Weltmeister Chip, Fabspeed Euro Pre-Muffler, M&K 1-in / 1-out Muffler 22 ERP /29 Sander Hollow T-Bars, Bilstein HD Struts / Sport Shocks ERP Poly-Bronze Bearings (A-Arms & Spring Plates), Stock Swaybars Turbo Tie Rods, '92 C2 5-Spoke wheels w/ 1" adapters, Drilled Zimmermans Yes, I drive mine as much as possible. If it's >32° & sunny, I've got the top down. 
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07-28-2009, 02:15 PM
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Join Date: Apr 2007
Posts: 95
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it started all of the sudden. no changed made.
To be more clear. Im not talking about those little pops which can be identified as 'irragular' firings. Im talking about massive explotions, like a 'mature' fire cracker. ok, so localizing an exhaust leak is not trivial. i was hoping for tip like using smoke at the intake or something. 84_carrera, i only have explotions when shifting. Thats hard to check then. Or will you have pops at idle too if it backfire at shifts? |
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07-28-2009, 09:27 PM
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