I bought a 89 rs, i live in alabama, so the cat was already cut off of the car since we dont have to pass emissions...

When i give it full throttle and let off, about 10 seconds later there is a loud explosion (its not immediate after letting off the gas, and alot louder than a normal backfire)

Is it because my cat is cut off but the smog pump/air pump is still on the car???

 

ha ha. Yes, block off the A.I.R. tubes coming off the manifolds. That will stop the popping.

If you have the carb then you have the choice of going back to the old timers glory days. you could get a Quadrajet, regular HEI dizzy (not a comp controlled one), EGR block off and rid yourself of the pump and all the hoses blocking the ends off. That should get you started.

Or you could just get a cat. your choice.

And remember if you gut it down to just a regular carb system, you can get busted for tamping or getting rid of the emissions stuff. then again who checks?

 

can i just unscrew the air tubes out of the manifold and then plug the manifolds and the car run fine? i dont care too much for ripping everything else out right now. but if i can just pull and plug the lines ill be happy with just that.

Do i cap the lines on the smog pump side? or do i just plug the manifold holes? or both?

 

also i do have a tbi

 

i believe theres an article for removing your air pump and lines in one of the forums either the tpi or tbi ones. you can unscrew the hard lines from the exhaust manifolds and get the correct sized plugs and screw those in.

 

well i just took some caps i had, and then capped off the two lines coming out of the back of the box and left the line that vented it to the atmosphere

will work for now i guess, havent driven it yet

 

i think a TBI will throw codes if you disable the pollution stuff.

also you have the plug the lines from the manifold or it will sound like you have an exhaust leak.

 

i dont know, didnt see a cel, but then again i bought this car abandoned and it had an 88 computer in it and a 88 ignition but in a 89 car (to get it to crank without the security)... so much is done to this car and i cant figure it all out yet. the cat was cut, a turbo 350 tranny was put in it, and the engine doesnt leak a drop, but i doubt its a 350 engine since all the smog is still on it (and no emissions testing in alabama)

 

The noise is a fuel-rich condition. Eliminating the A.I.R. won't change that, although it might be providing the oxygen needed to light it off.

Eliminating the cat changed the exhaust flow conditions that were assumed when the ECM was programmed. That's what you need to address.

 

i thought if it was a richness situation it would backfire after letting off the pedal, this happens like 10-20 seconds after letting off the pedal.... ? Sorry im a import guy, and this is my first v8

 

well anyways removing the AIR system will not throw a CEL

 

well see if it does not throw a code. and yes i had an 84 do exactly what is happening to you. I had true duals put on and not cat. It drove my computer nuts, it ran rich and as said before the air is causing it to ignite. easy fix, new cat. harder fix, gut it.

it's your car but the second option is more expensive then the first. parts get expensive after a bit.

 

cats are very expensive and easy to fix only hardest part is taking it off but once off just look in use a long screwdriver or something and hammer the insides out(do not breathe in). and no you will not get a CEL at all i have an 89 tbi and i gutted my cat removed my AIR system completely on stock computer and had no codes.

 

Where did you get true duals? Where they custom?

 

I have a 3.1l 1992 v6, I created my own true dual system by going to the junk yard, cutting the exhaust piping from another 3.1l, turing it upside down, routing it the same way the original piping is running however under the driver side. We cut the down pipe that ran under the oil pan, created a T pipe, and ran a second pipe down along the driver side. Ran into some complications going over the rear axle; panhard rod in the way, but you can get it over. That is an extreamly cheap way of doing it, only spending $50 in used piping from junk yard, getting some clamps and adapters, and using my dads trusty sawzaw. Exhaust shop would of charged around $600 - $800 to do everything new and professional.