What's this sound???
 

It happens when I'm backing off the gas when driving. It's kind of like a backfire only quieter. Only happens when I back off the gas after accelerating. Kind of like a blub, blub, blub sound That's pretty much the best way I can describe it!
I know others have this problem. Lean condition? Rich condition? Exhaust leak? What do you think?

Thanks
-Troy



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1995 GT Convertible, 5 Speed
Novi 2000 showing 9# of boost, Pro-M 77mm Mass Air Meter, 30# Injectors, 255lph Walbro Intank Fuel Pump, Bassani Equal Length Headers, X-Pipe & Cat-Back, Steeda G-Trac Stage 3 Suspension, Kenny Brown Extreme Sub System, Pro 5.0 Shifter, Cobra R Rims, FRPP King Cobra Clutch, Steeda Adjustable Clutch Quadrant & Cable

Does your x-pipe have cats? If not you could be hearing one of two things:

A) Not enough backpressure, so you get small lean pops.

B) You have a small exhaust leak somewhere, and cold air is rushing into your exhaust pipes and causing a backfire sound.

If the nut on my EGR valve is ont all the way tight, my car will backfire when I let off the throttle. If I get on it up to 6k and shift, it sounds like an M-80 went off in my back seat.

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1994 Mustang Cobra
308ci, Vortech S-trim 11#, ported GT-40 heads, E-303 cam, FMS 1 5/8 headers, BBK Offroad H-pipe, 2-chamber flows, and several other goodies.
Rebel Racing. Home of Bay Area Mustangs

I've got cats!

Do you have a bypass valve for that blower?

Are you sure it's coming from the motor and not from something rubbing?



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87 GT
Full exhaust, K&N, KB Subs, BBK STB, homeade dumps...


87 Taurus
New York
Winters Bite!

Got the bypass.
Nothing is rubbing.
People from other Stang sites say that it's very common. Lots of people even like the sound. Many think it's because of the change in backpressure from the new exhaust.
Sounds like a fairly good explanation to me.

-Troy

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1995 GT Convertible, 5 Speed
Novi 2000 showing 9# of boost, Pro-M 77mm Mass Air Meter, 30# Injectors, 255lph Walbro Intank Fuel Pump, Bassani Equal Length Headers, X-Pipe & Cat-Back, Steeda G-Trac Stage 3 Suspension, Kenny Brown Extreme Sub System, Pro 5.0 Shifter, Cobra R Rims, FRPP King Cobra Clutch, Steeda Adjustable Clutch Quadrant & Cable

It isnt your exhaust crackling is it??

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347 Stroker Motor: Balanced, 30lb Bosch Injectors, Cobra Computer, Cobra Transmission, GT40 Ported and Polished Upper and Lower, GT40 Milled Ported and Polished Heads, B303 Cam, BBK 1 5/8 Headers, March Underdrive Pulleys, Electric Fan, Accel Performance Coil, Accel 300+ Racing Wires, NGK Plugs, Ram Air, K&N Filter, 77mm Mass Air Unit, FlowMaster Exhaust w/offroad H-Pipe, Hurst Short Throw Shifter, 3:55 Gears, Ram Clutch, Cross Drilled Rotors, High Tolerant Painted Calipers and Drums.

Doesn't have a crackling sound. It's a deep blub, blub, blub sound. Happens when I let off on the gas after I get done accelerating. Hope I explained it effectively http://www.mustangworks.com/msgboard/smile.gif
Thanks
-Troy

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1995 GT Convertible, 5 Speed
Novi 2000 showing 9# of boost, Pro-M 77mm Mass Air Meter, 30# Injectors, 255lph Walbro Intank Fuel Pump, Bassani Equal Length Headers, X-Pipe & Cat-Back, Steeda G-Trac Stage 3 Suspension, Kenny Brown Extreme Sub System, Pro 5.0 Shifter, Cobra R Rims, FRPP King Cobra Clutch, Steeda Adjustable Clutch Quadrant & Cable

I know that on my stock 90, if I go from a full throttle rev, and just COMPLETELY let of the gas, it gives a couple pops, never worried me though.

try new plugs..one my buddiies uses that noise to tell when he needs new ones..or it could be an exhaust leak but if its a deeper sound then its usually an abundace on fuel i.e. bad spark

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1987 black notch(ex 4 banger)
DSS 306 w/ main support...Elderbrock 6028 heads..gt-40 intake..24# injectors...70 mm tb..77 pro-m...accel 300+..mac full legnth..tremec w/ pro5oh...full MAC exhaust,off road h-pipe,long tubes, catback...ron davis radiator..subframes, control arms...CFDF II..o yea holley FPR sucks..dont buy one..
AIM=onesillynotch

Is it driveline noise? or is it definitely exhaust noise? On my car if i let off the gas sometimes it does that.

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Joe!
1988 GT, 167,000 miles!!! 13.71@105mph Check out my listing! Click here! Or my website:
www.joe4speed.com
1999 Ninja ZX-6R 10.32@135mph!