I'm driving down the road and floor it in 3rd gear. Everything is fine until about 3200 RPMS when I start hearing this "rattling" noise. I just disabled the knock sensor 2 days ago so I thought it was detonation. The car also stopped pulling when this sound would arrive, a noticeable decrease in performance.

I drove it home and popped the hood. Revved the engine up and it sounds as good as ever. Pick up my dad (mechanic) and take him for a ride. I floor it in 3rd and 4th, and again at above 3000RPMS I hear the noise. He said it's definitely not coming from the engine, but from the exhaust area.

I've already established the fact the sound is not coming from the engine area or components.

Lately my voltage has been 1 volt lower (probably due to hotter temperature outside). But the lower voltage never seemed to affect the performance before

It's not just the noise, it's actually affecting performance for the worst.

Any ideas? Cat? muffler? Like I said, nothing to do with engine . Last year I got in an accident and my SLP muffler flew off and got pretty banged up. It was put back on the car. Could the internals have fallen apart?



------------------
91 Formula 1LE 1 of 46
305 TPI 5speed
1LE/G92/WS6

Paxton SN92 supercharger, Ford SVO 24#injectors, Crane AFPR,SLP airfoil, ported/polished plenum, March alt. pulley,Crane Gold 1.6rrs,MSD coil,MSD6AL (5400rpm limit),Holley 9mm wires,Ac delco R43ts plugs,custom chip,Bosch O2sensor,SLP 1 5/8" headers,SLP catback,shortened shifter,3:73s w/Auburn posi,180* t-stat,JET 195* fan switch, Macewen white face gauges, Autometer gauges, Zoom hi-performance clutch.

[This message has been edited by theformula (edited April 19, 2001).]

 

Or fuel pump. Could be starving for gas.

 

Im gonna guess PLugged Cat, It seems to simple


I dunno about that rattling tho, that sounds like valve Chatter or Ping.




------------------
60 Ranchero - Project ( Money Hole )
85 Sport Coupe LG4 - Daily Driver

Just another Hot Rod kid, or thats what they all tell me.
Livin' the Stereotype

 

Could be the fuel pump, but I closely watched the fuel pressure gauge under WOT and it was constant.

We've pretty much ruled out any engine problems . It just started happening tonight.
Earlier today it didnt do this.

By the way, to further rule out the engine. I popped the hood and revved it to 5k a few times. No funny sounds at all. Very smooth.

 

I just went out and banged the hell out of my SLP exhaust and cats. The only thing I heard was a vibration. No rattling or loose things. However, I took the car for another drive and it almost sounded like a popping sound this time. Like it WAS the cat. That may be the problem. Like I said, there IS a noticeable decrease in performance.
Thanks for the replies

 

Damn, that doesnt sound right lol

 

Sounds like the cat to me! Personally what I would do is unbolt the exhaust after the cat (if you can), then get the cat REALLY hot! Once it's really hot, take some ice cold water from somewhere and spray the cat...this should help break up some more of the stuff in there! Then start the car and rev it up several times...pretty high...and see if you can't get the crap to come out the cat!!

Or you could just replace the cat or cut it off, like I did, and weld a pipe in it's place!!

 

Gutting the cat is a pita on my car since I have dual cats. It's also kind of fun using your dremel trying to cut the pipe ..praying you don't hit the air tube.

Looks like I'm going to end up gutting it. Damnit, another $75 to blow at Meineike

Damn money pit of a car