While driving the stang the other day, it started making a noise kinda like a plastic bag stuck under the car but definitely wasn't. After a minute or two the noise stopped but car started shaking both at idle and while driving in gear and the exhaust tone changed. After getting the car home I noticed the serpentine belt was starting to come apart. I just finished changing the belt but the car is still shaking. There's enough shaking even with a smooth idle to keep banging the CAI against the strut tower. There is not as much shaking while driving in gear but you can tell something is not right. Also, I don't know how to describe the sound but the exhaust tone is different. It's not quite muffled but it's far from the normal throaty sound. I replaced the motor mounts about 10K miles ago when I did my headers. I have no idea where to start other than maybe the harmonic balancer...if anybody can help or has any ideas it would be greatly appreciated.
Need Help...Car has started shaking and exhaust tone is different
- Thread starter haoleboy72
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Chrome_Rust
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The Wife's notch did the same thing to me... (hers is a 4cyl) Head gasket. Check coolant for air bubbles, and milkshake looking stuff in the oil....
Might be a miss also, check plug wires for burn through, pull plugs for wetness from fuel or coolant....
Might be a miss also, check plug wires for burn through, pull plugs for wetness from fuel or coolant....
You may want to check your balancer it could be wobbling or if that not the problem check the header gaskets i blew one last week and it made my 5.0 real loud. See if you can hear a tick tick noise with your motor idling if you hear this it's the header gaskets.Check your oil an if it's not milky in color and if you don't see clouds of white smoke and if your not running hot it's not the head gasket.But i would look at the balancer because it had to be a reason way your belt was messed up.But check those thing out good luck.
I was going to suggest checking the plugs and wires. I have had the plugs back out before and pop off.
It's been a while but I finally got around to working on the stang. Replaced the alternator w/ a 6G...not sure why anybody would go thru the hassle of a 3G when the 6G is so easy! Replaced the A/C compressor because the bearings on the one in the car were shot. I also replaced the Air Intake Charge Sensor...for anybody having idle issues I recommend checking this because my idle wasnt bad (would search til the car warmed up) but now as soon as I start it, it goes right to idle! However, the car is still shaking and the exhaust tone still isn't what it used to be. I have O-ringed heads and there's no white smoke or milky oil so dont think it's a head gasket. The car idles fine other than the shaking (not missing), so I dont think it's a plug or wire type of thing. Visually checking the balancer and appears to be fine...anybody got any other ideas? The car is driveable right now but not running 100% of the way I know it can. Thanks for any help anybody can offer! 
the pony boy
Founding Member
I will check the timing and for vacuum leaks. All this started after my belt started to come apart...wondering if the belt hit something while whipping around under the hood. Anybody have a Mass Air Sensor go bad before? wondering if maybe the belt hit the sensor/meter causing it to not read correctly. I forgot to mention in the last post that when I took it out for a test spin that it backfired a couple of times and it felt a little laggy when accelerating. Maybe the belt hit the distributor and moved...looking for more ideas.
When i blew the head gasket on my 302, it didn't smoke and my oil looked fine. It blew out between 2 cylinders so no oil was getting burned or leaking into the coolant...it shook like it was about to fly apart and sounded really strange but didn't smoke at all.
Repostyle
Member
silverone 1
Member
not knowing your exhaust set up,this has personally happened to me with the engine getting rough and sounding as though thiers a bag under the car. It turned out to be one of my catalytic converters(after market) desinegrated and chunks got lodge in the exhuast hence the farting,weezing,plastic bag sound, plus all the clogged back pressure changed the idle and at the lower rpm's. The car would also run better as i accelerated due to pressure getting forced out more.Dont know if this could be your situation but you deffinately dont want it going on for long/the extra backed up heat will not be good for exhaust valve/head/header.It took a bit to figure out because it was symtematic to what all the other posters have suggested.
How in the world did you figure that one out!?! I wonder if my issue is a cause of my JBA's. Read post called "HELP ME". Glad you found the issue, but that must have been a nightmare to track down.
My exhaust setup is MAC shortys w/ Magnaflow H-pipe w/ cats and MAC catback. The exhaust tone is kinda rough almost Nascar sounding instead of the normal throaty 5.0 sound. The MAC exhaust has a very similiar sound to Flowmaster. I don't have the plastic bag sound anymore, think that was related to the belt coming apart. My heads are O-ringed and I used the O-ringed Fel-Pro gasket and my heads were redone between the last 5-10K miles. I will look into the compression test (never done before). The car doesn't overheat at all. It seems to rev normal in neutral other than the exhaust sound, but once it's out on the road it seems to pull when accelerating but then will pull a little hard then a little harder...really wierd. I just find it odd that this started happening right after the belt came apart. That's what leading me to believe that the belt might have hit something like a vacuum line or sensor or the distributor. I appreciate all the help from everyone. I am looking into checking the timing and doing a compression check and looking for loose vacuum lines. Crazy thing is that it still idles normal and it doesn't miss at all...
