Enormous "Pop" noise at startup! - 2003-04 Mach 1 Registry Owners Club

twomachs · 08-29-2003, 11:27 AM

I have an occasional gigantic "pop" noise on startup. I think it is from the rear and sort of like a backfire but not really. Sometimes it sounds like it is coming from the left rear speaker!

I took it to the dealer and they did a tech search and came back with "normal condition" but it sure sounds bad. Catches me off guard sometimes.

Anyone else experience this?

IamI · 08-29-2003, 12:05 PM

This may be unrelated and actually comes from the front, but when the AC is turned on one of my hoses slaps the firewall quite loudly. Sometimes the sound is quick enough to be hard to pinpoint location. Of course after warming up some it seems better.

The dealer basically said we would have to monitor the sound as it was not doing it when the service tech was in the car.

May not be what you are hearing, but thought I would mention it.

twomachs · 08-29-2003, 01:07 PM

My AC has been off when this happens but it doesn't mean it couldn't be related. This sound only happens once when it occurs - even if the car has been sitting several hours before starting again. I am trying to see if cooler/humid mornings have more coorelation to the problem or not.

It actually is so loud sometimes that it sounds like a small canon went off. No smoke or residue at the tailpipes (or piston pieces on the ground!).

Thanks for the reply.

rocketmach · 08-29-2003, 03:28 PM

I've heard the same thing and believe it is the rear speaker amps popping as well.

tallymach1 · 08-29-2003, 03:36 PM

Try it without your radio on and see if you can get it to do it. If the amps coming on are causing that noise, it will destroy your rear speakers quick. You would know if it was a backfire from the engine, you would think someone just shot a gun at you.

Shaker1 · 08-29-2003, 04:17 PM

This is covered in the Mustang Workshop Manual on page 415-00-2: "Loud Popping When Cycling the ignition switch" It directs you to pinpoint test I. The gist of it is you need to send the "audio unit" in for service. In the case of convertibles it can occur in either LH or RH subwoofer amplifiers. Here it instructs to test circuit 173 (LH) or circuit 174 (RH). These are DG/VT or GY/BK colored wires on the subwoofer amplifier C4108b/C4109b (LH/RH) connectors (pin 2). From harness side to ground voltage should be indicated.

I would check the connecters to the subwoofer amps and remove and replace them (reseat). If that did not work there could be a problem with the audio unit requiring repair or replacement.

twomachs · 08-30-2003, 11:03 AM

Quote:

Originally posted by Shaker1
This is covered in the Mustang Workshop Manual on page 415-00-2: "Loud Popping When Cycling the ignition switch" It directs you to pinpoint test I. The gist of it is you need to send the "audio unit" in for service. In the case of convertibles it can occur in either LH or RH subwoofer amplifiers. Here it instructs to test circuit 173 (LH) or circuit 174 (RH). These are DG/VT or GY/BK colored wires on the subwoofer amplifier C4108b/C4109b (LH/RH) connectors (pin 2). From harness side to ground voltage should be indicated.

I would check the connecters to the subwoofer amps and remove and replace them (reseat). If that did not work there could be a problem with the audio unit requiring repair or replacement.

Thanks guys. I will reseat the connectors like you suggest Steve.

The radio has not been on when this happens although sometimes when cruisin' around I think I have sort of heard a similar, but softer, noise from the left rear speaker.

It does sound like a gun-shot Tallymach1 - sometimes louder than others but only once a day when it happens. But not always. I an first did think it was a backfire and that is what I told the dealer service center. Since that time it seems it is from the speaker area.

I appreciate the references and I will check it out this weekend and I am glad a couple of other owners like Rocketmach have noticed some similar sounds. You all are from warmer climates so the temperature probably doesn't make a difference.

If I can't solve it I will take it in again armed with this information.

codymach · 09-02-2003, 12:13 AM

I get a slap or pop sound too when I turn on the AC..........

Shaker1 · 09-02-2003, 06:04 AM

Quote:

Originally posted by codymach
I get a slap or pop sound too when I turn on the AC..........

http://www.mach1registry.org/forums/...ht=a%2Fc+noise

twomachs · 09-02-2003, 05:44 PM

Quote:

Originally posted by Shaker1
http://www.mach1registry.org/forums/...ht=a%2Fc+noise

I don't think mine is the AC. Nothing is on at all - I am just starting the car and it happens within seconds.

I R&R the amplifier leads but it still has done it once in the last few days. The search continues.

But thanks for all the suggestions.

08-29-2003, 11:27 AM	#1
twomachs R 32V Join Date: Jul 2003 Location: Plymouth, MI Posts: 43	Enormous "Pop" noise at startup! I have an occasional gigantic "pop" noise on startup. I think it is from the rear and sort of like a backfire but not really. Sometimes it sounds like it is coming from the left rear speaker! I took it to the dealer and they did a tech search and came back with "normal condition" but it sure sounds bad. Catches me off guard sometimes. Anyone else experience this? __________________ 1936 Ford Tudor street rod 1969 Cougar conv., 351W-4V, 4spd (under construction) 1970 Mach 1, Red 351C-4V shaker, C6 auto 1989 Trans Am GTA (I know!) 1997 Cobra conv., Pacific Green Metallic/Tan/Tan 2003 Mach 1, 5spd., Torch Red, IUP

08-29-2003, 12:05 PM	#2
IamI Registered User Join Date: Jul 2003 Location: Franklin, TN Posts: 28	This may be unrelated and actually comes from the front, but when the AC is turned on one of my hoses slaps the firewall quite loudly. Sometimes the sound is quick enough to be hard to pinpoint location. Of course after warming up some it seems better. The dealer basically said we would have to monitor the sound as it was not doing it when the service tech was in the car. May not be what you are hearing, but thought I would mention it. __________________ 2003 Mach 1 Torch Red 5spd IUP K&N filter 1995 GT Teal 5spd Tinted Windows K&N filter 1971 Cougar 351 Cleveland 3sp auto with shift kit ( Started my interest in more powerful cars)

08-29-2003, 01:07 PM	#3
twomachs R 32V Join Date: Jul 2003 Location: Plymouth, MI Posts: 43	My AC has been off when this happens but it doesn't mean it couldn't be related. This sound only happens once when it occurs - even if the car has been sitting several hours before starting again. I am trying to see if cooler/humid mornings have more coorelation to the problem or not. It actually is so loud sometimes that it sounds like a small canon went off. No smoke or residue at the tailpipes (or piston pieces on the ground!). Thanks for the reply. __________________ 1936 Ford Tudor street rod 1969 Cougar conv., 351W-4V, 4spd (under construction) 1970 Mach 1, Red 351C-4V shaker, C6 auto 1989 Trans Am GTA (I know!) 1997 Cobra conv., Pacific Green Metallic/Tan/Tan 2003 Mach 1, 5spd., Torch Red, IUP

08-29-2003, 03:36 PM	#5
tallymach1 Registered User Join Date: Jun 2003 Location: Fl. Posts: 302	Try it without your radio on and see if you can get it to do it. If the amps coming on are causing that noise, it will destroy your rear speakers quick. You would know if it was a backfire from the engine, you would think someone just shot a gun at you. __________________ 2004 Cobra 2003 procharged mach 1 : deceased

08-29-2003, 04:17 PM	#6
Shaker1 Living The Dream Join Date: Sep 2002 Location: IL Posts: 2,112	This is covered in the Mustang Workshop Manual on page 415-00-2: "Loud Popping When Cycling the ignition switch" It directs you to pinpoint test I. The gist of it is you need to send the "audio unit" in for service. In the case of convertibles it can occur in either LH or RH subwoofer amplifiers. Here it instructs to test circuit 173 (LH) or circuit 174 (RH). These are DG/VT or GY/BK colored wires on the subwoofer amplifier C4108b/C4109b (LH/RH) connectors (pin 2). From harness side to ground voltage should be indicated. I would check the connecters to the subwoofer amps and remove and replace them (reseat). If that did not work there could be a problem with the audio unit requiring repair or replacement. __________________ 2008 GT500 Alloy W/ Silver JLT/EVO tune BMR LCAs Last edited by Shaker1; 08-29-2003 at 08:49 PM.

08-29-2003, 03:28 PM	#4
rocketmach Registered User Join Date: Jul 2003 Location: Reno Nevada Posts: 49	I've heard the same thing and believe it is the rear speaker amps popping as well.

09-02-2003, 12:13 AM	#8
codymach Registered User Join Date: Jun 2003 Location: somewhere Posts: 2,840	I get a slap or pop sound too when I turn on the AC.......... __________________ SUPPORTING MEMBER MODIFICATIONS: Bassani Mid-Length Ceramic Headers Bassani X-Pipe with cats SS Bassani Cat Back SS Meziere Electric water pump PHP Intake Spacer KN Filter Hurst Retro Shifter, T-handle Bullitt Fuel Door Bullitt Anthracite 18x9 wheels Goodrich g-force T/A KDW 265/40/18's Hurst Equipped Emblem Mach 1 I.D. Plate Shock tower covers Raised the shaker 2003 Mach 1 Torch Red 1965 Rambler Marlin 287 (Slowest car in the West!) 1951 Mercury (still in the field) 1966 Ford Galaxy 500, 352 cu. in. 4v 1994 F-150 4x4 2001 Focus

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