92 camaro RS catalytic converter smoking

[jmy667]

I just rebuilt a 92 3.1 TBI engine. After starting it for the first time and letting it run for the 30 minute break in, it back fired through the exhaust about every 30 seconds to a minute. Smoke began to blow out of the catalytic converter. The exhaust got so hot it boiled the fuel in the fuel tank. Luckily it did not explode. I replaced the catalytic converter yesterday. I started it and adjusted the timing. It is still backfiring through the exhaust about every thirty seconds to a minute. Once the engine gets to operating temp, the new catalytic converter started smoking. Exhaust is making it to the muffler and tail pipes. I shut it down and I am currently stuck on what to check. Is it possible that fuel is getting to the exhaust or that it is running to lean? I do have one vacuum line that I cannot find where it goes. The line comes from the regulator on the fuel rail to a tee. At the tee it branches off to a long hose. This is the one that I have no clue to where it goes. The other side of the tee is connected. I do have a manufacture shop manual but it does not show a vacuum diagram. Any suggestions anyone?

[biglistofmods]

sounds like you have some crossed wires or just a plain old misfire.
and for the love of god set your timing with a timing light!

[biglistofmods]

btw a 92 3.1 is a roller motor you don't have to break in roller motors.
engine break in is for flat tappet motors.

[jmy667]

I have check the firing order and it is correct. Timing is set to 10 degrees BTC and was set with a timing light for gods sake.

[biglistofmods]

for gods sake good!
does it pop while your on the throttle or just at idle?

[jmy667]

It pops both at idle and while increasing throttle. While increasing the throttle though the popping is more frequent.

[biglistofmods]

sounds like a sticking valve.
check the data stream and see how all the values are.

[jmy667]

Not sure what you mean by data stream.???

[4onFloor]

Originally Posted by biglistofmods

sounds like a sticking valve.
check the data stream and see how all the values are.

he'd have to have a scanner to read data tables

Originally Posted by biglistofmods

btw a 92 3.1 is a roller motor you don't have to break in roller motors.
engine break in is for flat tappet motors.

it's still a good idea to break in the engine to properly seat rings

if your exhaust is getting hot enough to boil the gas in your tank, i think you have something making the cat run extremely hot, like gasoline

[biglistofmods]

your cam timing could be off.
if it was retarted it would get your exhaust extremely hot.

[jmy667]

The timing is at 10 degrees BTDC which is what the book calls for. If the it was running to lean would it not cause the cat to get hot?

[4onFloor]

Originally Posted by jmy667

The timing is at 10 degrees BTDC which is what the book calls for. If the it was running to lean would it not cause the cat to get hot?

that's your ignition timing. did you change the timing chain and or cam before you put this motor in? if you didn't than i wouldn't worry about it

[89IROC&RS]

do you have any burned wires??? is your cap shorting across terminals, your ICM could be going bad, bad coil perhaps. although it does sound like its running rich, or worse, you could have a slight coolant leak. which would burn up cats.

[89IROC&RS]

um, question, you didnt break in the engine with synthetic oil did you?

[jmy667]

Yes I did change the timing chain, cam, distributor, coil, etc. There is nothing that I did not change. And yes the timing marks were lined up. I am not losing any coolant from the radiator so I do not think there is a leak. No I did not break in the motor with coolant. I am going to check the A.I.R pump in the morning. I was reading in the manual that if it is not working properly then the ECM will by pass the O2 sensor sending to much oxygen to the cat causing it to over heat.