Yesterday I removed the circular pipe that goes from the air intake to the exhaust manifold on the stock 305 TBI from my 1992 Camaro Rs because it had a small crack in it. I haven't replaced it yet but noticed today while I was driving my check engine light came on.

I degreased the engine three days ago and it misfired a bit and was really bogging when I hit the gas, but it dried out and is fine now. The car runs just fine and I assume the Check Engine light came on due to engine misfiring, but now it still comes on. I have to drive the car a bit for it to come on, but eventually it will.

New spark plugs and wires are in.

Can this hole cause a vacuum in the exhaust THAT BAD so that my check engine light comes on?

The car is driving fine.

 

No, the pipe you removed only provides warmed air to the throttle body to help the engine warm up faster during cold mornings. It has no effect on the computer, but is still considered part of the emissons devices.

You need to do the paperclip trick to find out what code is store in the computer. See the FAQ or Tech Articles section on this website to find out how to stick a paperclip in the ALDL and make the SES light flash its codes.

 

I'm no expert here, but I can confirm one hundred percent that removing the pipe from the exhaust to the intake will not cause the SES light to come on.

As Kevin mentioned above, that is a cold-start emissions device and it has no bearing on causing the computer to throw an error code.

Look to your recent degreasing. Find out which code your computer is throwing.

However, with your degreasing, you might have fouled up a few different sensors with water. You might be chasing your tail for a bit, in which case time will dry out the sensors probably.

 

The pipe you removed is the stove pipe. You dont need it really. It doesent make vacuum or carry it. What happens, is when it is cold out, the car sends vacuum to that little line that plugs into the aircleaner snorkel. The vacuum opens a diverter called the Thermac valve in the snorkel. This allows the car to feed on warm air from around the exhaust manifold to help vaporize the gas. The car will run fine without it tho.

As for the misfire and bogging, you should really check your cap and rotor. When I first bought my car, it did that whenever I rinsed the engine or washed the car. Over a few more months, it got worse and worse, to the point that it wouldnt even run in light rain or humid weather. Took me forever to figure out what it was.

Finally, I tried to replace the cap. The screws broke off in the distributor base. I kept the stock Ign module as a backup, and brought the stock dizzy back in as a core to autozone. I was able to get a reman dizzy from cardone for $100. With its own new module, p/u coil, points, all that. I also got a Duralast Gold cap + rotor kit. Its a great cap + rotor with brass contacts instead of the pot metal like the stock one.

Dropped in the new dizzy with rotor, threw on the new cap, plugged all the wires in, and set base timing. Runs great now, even in the worst weather.

 

That begs the question, shouldn't you cover your distributor and battery before starting any engine bay cleaning?

 

usually it can be a good idea to cover the distributor cap....

however, you have to realize, everything under the hood **that is in good working order** has some decent resistance to water. The engine bay is not sealed to the elements like the passenger compartment remember.

As for the distributor, there is a little screened vent in the base. So that isnt even designed to be sealed. If water does get in, it can at least exaporate out. On my origional distributor, this screen vent was completely clogged with powder from the contacts that had disentigrated. That probably caused moisture to get locked inside the cap, and caused the points / p/u coil / module to rust and fail.

Notice the corossion on the cap's contacts:


Notice the white metal disentigrated and formed a pile towards the back. Also, look at how rusty the points are...