Both Mufflers Exploded.......What's wrong?

ram360

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Oct 19, 2002

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Pennsylvania

Dec 18, 2003

#1

• Dec 18, 2003

• #1

My friend picked up his 87 GT yesterday. It's a pretty nice car, but I'm somewhat concerned. We were aware the mufflers were blown out before purchasing the car. I just assumed it was from age, rust, etc.... However the previous owner told him something along the lines of when he went to start the car one day both muffs exploded, and it was because the car was getting too much fuel because the FP wasn't adjusted. (I wasn't there to hear the guy explain all this to him) When I had my chance to look at the car. I looked under the hood and it still has the stock FPR. I've never saw anything like this before. Both muffs look like someone put some explosives inside each one and set them off. Motor is 100% bone stock, stock headers, stock h-pipe, just an exploded cat back, and gears? Any ideas?

 

ram360

Founding Member

Oct 19, 2002

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Pennsylvania

Dec 18, 2003

#2

• Dec 18, 2003

• #2

.....The gas pedal sticks too

 

T_5.0_N'works

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Sep 30, 2003

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Texas

Dec 18, 2003

#3

• Dec 18, 2003

• #3

I dunno but in my 69' Chevy I had(carb'ed of course) backfired I believe cause it was super loud and both mufflers exploded that I had on there, quite funny.

 

J

jerry beach

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May 20, 2002

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Ocala,FL

Dec 18, 2003

#4

• Dec 18, 2003

• #4

Dont drive or ride in that thing till the gas pedal is fixed. I have heard of mufflers blowing up, but have never seen it happen, got any pics? Raw gas in the muffs and a little spark is all it takes. You can cause a carbed car to backfire in the exhaust by turning off the key while you are driving and leaving the tranny in gear. This will dump fuel into the exhaust. After a couple of secs, turn the key back on and boom! I dont think this should work on an EFI setup unless something is wrong with it. Pull the codes for starters, and I would be checking the FP, maybe the FPR went south and its dumping tons of fuel.

 

maverick0716

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Jan 12, 2002

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Chilliwack, BC, Canada

Dec 18, 2003

#5

• Dec 18, 2003

• #5

When mufflers explode like that its from fuel pooling up in them (mostly on chambered mufflers like Flowmaster) and eventually the gas ignites and blows a hole in the muffler........so yeah the guy is right, it's definitly not burning all the gas in the combustion chamber. Try checking the spark plugs, timing, etc...

 

ram360

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Oct 19, 2002

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Pennsylvania

Dec 18, 2003

#6

• Dec 18, 2003

• #6

Ok, Thanks guys. I have an extra FPR laying around so we'll put that in for starters. I don't have any pics but I'll try to get some. That's scary. BTW any ideas on how to free up the sticky gas pedal?

 

T

tbird187

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May 29, 2002

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Indiana

Dec 19, 2003

#7

• Dec 19, 2003

• #7

I had both my mufflers explode literally when my throttle got stuck wot and i kit the key off then back on.......... scary times

 

Fox Saleen 163

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Dec 5, 2003

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San Diego, CA

Dec 19, 2003

#8

• Dec 19, 2003

• #8

First thing you may want to check is the Vac line going to the FPR. Does it have Vac? Pull the Vac line off at idle, if you put it on your finger it should stick to it like a house Vac would.

 

1

1hot5.0

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Sep 6, 2002

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Surprise, Arizona

Dec 19, 2003

#9

• Dec 19, 2003

• #9

Check to make sure the idle adjustment screw is not sticking by the throttle body.

 

BlackFox5.0

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Aug 7, 2000

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Dec 19, 2003

#10

• Dec 19, 2003

• #10

Fox Saleen 163 said:

First thing you may want to check is the Vac line going to the FPR. Does it have Vac? Pull the Vac line off at idle, if you put it on your finger it should stick to it like a house Vac would.

Click to expand...

Some AFPR's look like the stock one, once you pull the vacuum line you will see a screw on the part the hose was connected to, the stock one does not have this....

 

JadeFalcon

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Mar 28, 2002

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Arlington, TX

Dec 19, 2003

#11

• Dec 19, 2003

• #11

yeah, I've seen this happen. Normally it happens when there is an intermittant ignition problem, like a wet TFI module or something, where spark is beign killed and raw fuel is being dumped into the exhaust, if you get enough of it far enough back and it ignites, those restrictive rusted stock mufflers will explode, and it is LOUD.

 

0

00 Red SS

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Jan 22, 2003

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Grain Valley, MO

Dec 19, 2003

#12

• Dec 19, 2003

• #12

when i was 16 i started my car in the garage and felt a big explosion and the garage was a cloud of smoke, i had no friggin clue what happened untill i looked under the car

 

ram360

Founding Member

Oct 19, 2002

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Pennsylvania

Dec 21, 2003

#13

• Dec 21, 2003

• #13

We replaced the FPR last night. I figured that was a good place to start. The gas pedal on the car is very weird. When the car isn't running you can push the pedal and it works just fine. Opens the throttle very smooth and works fine applying the normal amount of pressure to the pedal so the cable is fine (not kinked, or binding on anything). Once the car is running the gas pedal is difficult to push down (feels as stiff as the clutch pedal) I'm totally confused on this one.

 

ram360

Founding Member

Oct 19, 2002

2,162

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Pennsylvania

Dec 21, 2003

#14

• Dec 21, 2003

• #14

Fox Saleen 163 said:

First thing you may want to check is the Vac line going to the FPR. Does it have Vac? Pull the Vac line off at idle, if you put it on your finger it should stick to it like a house Vac would.

Click to expand...

All the vacuum lines seem to be fine.

Some AFPR's look like the stock one, once you pull the vacuum line you will see a screw on the part the hose was connected to, the stock one does not have this....

Click to expand...

The reg on the car non adjustable but was bigger than those found on stock 5.0's. We replaced it w/ an oem part.

Check to make sure the idle adjustment screw is not sticking by the throttle body.

Click to expand...

This also apprears to be functioning as normal.

 

D

DaveB

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Jul 13, 2002

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Middlesex and Pomona, NJ

Dec 21, 2003

#15

• Dec 21, 2003

• #15

The same thing happened to my neighbors old Pontiac LeMans. Didn't get in depth, but said a backfire caused both mufflers to explode. He said a welded muffler (ie. Dynomax Ultraflow Welded) would have been fine.

 

ram360

Founding Member

Oct 19, 2002

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Pennsylvania

Dec 21, 2003

#16

• Dec 21, 2003

• #16

JadeFalcon said:

yeah, I've seen this happen. Normally it happens when there is an intermittant ignition problem, like a wet TFI module or something, where spark is beign killed and raw fuel is being dumped into the exhaust, if you get enough of it far enough back and it ignites, those restrictive rusted stock mufflers will explode, and it is LOUD.

Click to expand...

So it's possible it's an ignition problem? Like I said other than the gas pedal being siffer than normal, everything else if functioning as normal. The cap and rotor look good, however the previous owner said it has Bosch platinum +4's in it. I'm wondering if they are causing the problem w/ a misfiring cylinder or something. I never understood how you get the gap correct on a 4 prong plug?

 

Carney Woods

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Dec 29, 2002

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Montreal, Quebec

Dec 21, 2003

#17

• Dec 21, 2003

• #17

Check the throttle body blade it's possible it's sticking to the housing........