Shift to 2nd gear... POP... help me figure this out...

[MustangThief]

Hey guys...

Got some brand new Hoosiers on the car today so took it for a few spins with my bud. It sounded like I had a slight exhaust leak since I got my X-pipe put on but I never thought much of it.

Anyway, I floored it through first, shifted to 2nd, and as soon as I shifted into 2nd we heard a LOUD *POP*. At first I thought it was the halfshaft or transmission because it sounded like it was from underneath the car, almost near the midsection.

Anyway, I was only a block from the house so we quickly pulled in and shut her down.

Now, I'll try to get a vid up tomorrow but it was already dark so we didn't mess with it much, only started it a few times to listen/smell and try to figure out what the hell I did.

When it turns over you can hear air escaping, and when I start it up and let it idle it idles fine, you can hear the air from the passenger side still with it idling. When you turn it off you can hear 3-4 seconds of air escaping out. When I tried to give it a little gas it sounded fine but had a lot of lag in the gas peddle like I had horrible back-pressure.

My buddy and I are thinking I blew the exhaust gasket manifold or possibly the donut gasket that bolts to the x-pipe?

Also, after turning it off it did smell like exhaust gas under the hood.

Could it be something worse?

I guess this weekend I'll be pulling the exhaust off the car to see what the hell is going on. But I was hoping with the symptoms you guys could help me pinpoint this.

Any questions just post.

Thanks for any help you guys can provide.

 

[slowr w/o blowr]

check to see you dont have a vacuum leak after your mass air sensor. I've banged second gear real hard once and knocked off my pcv line. run like crap and acts like what you are explaining.

 

[BIGV]

If you smell exhaust under the hood you have an exhaust leak. You should be able to track it down by listening for it. When I put my x-pipe on it sounded horrible like it had a leak. Popped the hood and could smell exhaust went back under and found the passenger side not seated correctly. Realigned and it was fine in your case you heard a pop sounds like you blew something out and exhaust is leaking. If you did blow out the gasket you should be able to hear it.

 

[MustangThief]

If you smell exhaust under the hood you have an exhaust leak. You should be able to track it down by listening for it. When I put my x-pipe on it sounded horrible like it had a leak. Popped the hood and could smell exhaust went back under and found the passenger side not seated correctly. Realigned and it was fine in your case you heard a pop sounds like you blew something out and exhaust is leaking. If you did blow out the gasket you should be able to hear it.

When I first listened under the hood I could have sworn the air escaping sound was coming from the passenger side valve cover area. But the damn 4.6 is so sardine crammed into that engine bay I think I just heard it coming up from behind/side of the motor and it sounded like the valve covers.

I'm planning on pulling off the x-pipe today to see if the gasket going to my stock manifolds is jacked up. If it's the manifold gasket to the head then I will probably have to take it to a shop, since where the car is at is a gravel driveway...

 

[AaronK]

I'm betting exhaust leak. If you heard a loud POP and it's running/idling like crap, then my first guess would be header gasket. But if they are stock manifolds/gaskets, I don't know if I've seen to many of those go bad.

 

[JB]

are you running cats?

 

[MustangThief]

are you running cats?

Neg.

Stock manifolds, Off-road X-pipe, Flowmaster Cat-back

 

[MustangThief]

Well we got it up in the air last night, pulled the X-pipe off, and the passenger side flange gasket was pretty tore up. Replaced it, got everything back together...

Started it up, as soon as it went to turn over it made a small pop and started running like shit immediately. The motor itself sounds fine to me, but again, lot of exhaust smell under the hood, with very poor idle/shakey idle.

So I guess I'm down to it being the exhaust manifold gasket or something with the motor even though I couldn't imagine it being something with the motor since the motor sounds fine and it has a rich exhaust gas smell.

I just can't see how that woulda happened, it's the stocker manifolds...

Guess it's time to get it flatbedded to the shop... I guess I'll have em yank off the manifolds and weld on my FLSFCs while they're at it.

I kinda wanna wait and get some long tubes but if it ended up not being the manifold gasket i'd be up money-shit-creek if I already had long tubes and the sub frames on

 

[SLPRCTM]

I may be way off on this one but have you checked to make sure you didn't pop out a spark plug? This would explain the loud "pop" sound, the car not running well and the rich/unburnt fuel smell from the exhaust. Just something to check out......

 

[03_SVT_COBRA]

check your spark plugs. if they look ok, and the threads look ok, do a leak down test on that passenger head. make sure the valves are closed in the cylender testing. check places like head gasket area, pull the oil dip stick and stick your ear on it. then turn the engine so the exhaust valve opends then check your headers x pipe ect. if its exhaust related you'll hear the air. easy fix. good luck!

 

[MustangThief]

I may be way off on this one but have you checked to make sure you didn't pop out a spark plug? This would explain the loud "pop" sound, the car not running well and the rich/unburnt fuel smell from the exhaust. Just something to check out......

Ding ding. We have a winner.

Pulled the plugs today and the 2nd to last one on the passenger side was blown out. It looks like I may have cross-threaded this one last time I changed them, because the first three threads on the plug were stripped.

Put one of my old plugs in and it started to tighten and then kicked out and wouldn't start threading.

SO... I guess I'm going to tap it with the same size and see if I can get away with just re-threading it.

I don't have to pull the head off to try to tap it with the same size right? I heard you can just grease the end of the tap to catch any of the little bit of shavings since it's the same size.