HELLO, I just bought an 89 Formula 350. Its all stock except for a Flowmaster catback, custom y pipe, and the cat has been removed. Its seems a lil bit raspy and loud and when Im at idle there is a loud hissing sound coming from under the car. But when I give it a lil throttle it seems to go away. is this an exhaust leak or does it have something to do with the cat being removed. its throwin me a check engine light(not sure which code yet) and it seems a lil sluggish off the line. any help would be greatly appreciated!!! thanks

 

did you remove the air pump from the engine after you removed the cat? theres a line that runs from the air pump to the converter maybe that's your culprit. And do you know what number code it's throwing? that'll help alot. it's pretty easy just jumper the top two ports on your aldl port turn the key forward (don't start) and count flashes. it'll flash 12 3 times then whatever your error code(s) are 3 x's and then start going with 12 again when it's complete.

 

well i just bought the car today so Im not sure if the air pump is still there. but im guessin that it should be on the passenger side of the motor under the ac compressor (if its there). and what do u mean jump the 2 top adl ports? is there a certain kind of electronic tool i need to do this? any info is greatly appreciated!!

 

the only special tool you need is a paperclip, it flashes kinda like morse code (as in short pauses and long pauses) like code 12 3 times would be flash...flash flash............flash...flash flash............flash...flash flash

 

Alright, RIGHT after I took off my Cat. it made this whistling sound also, I figured it was where my buddy couldnt weld above the pipe near the car, so, the next day I put JB Weld ALL around the weld marks, and by george that fixed the whistling problem.

As for the AIR Pipe, turns out, we cut it off to get to the Cat. but it turns out that hole was plugged on the converter!

What we did was drill a hole in the pipe we replaced the cat with and welded that AIR pipe back on.

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NOW, a couple weeks later, my car started to Idle REALLY rough one day and gave an engine code, turns out to be my MAF sensor, so, I replace my MAF sensor and it doesnt help ANYTHING!

My engine is being rebuilt top to bottom at the moment, so, hopefully the problem will be fixed when I get it back.

My question is this, do I need to have that AIR pipe plugged since it was found like this after we cut it off to weld back on to the cat.?

 

that is a good question! Im kinda hoping someone could answer that buddy. Cuz this whistling under the car is really loud and annoying. And it feels like it might be costing me a few horses!

 

Why the hell would you weld the air pipe into an exhaust with no cats? This is one of the dumbest things I've ever heard. The only reason the AIR pipe to the cat is there is to cool the beds in the converter.

 

Well, The only way to find out would be to crawl under the car when its making that noise and find out where its coming from.. Make sure you set the E-Brake!..

 

If it's a hiss I'de blame the pump, if it's a hiss with a tick at certain rpm's I'de blame the welds. Drive by something like a big building close to one side of the car, then the other side and see if you hear a tick tick tick or just a constant hiss. Anywhere that exhaust is leaking out will turn black after a while, so you may want to try taking a mirror and a flashlight and checking all around the welds for blackened spots.