Ok, here is the situation:

1985 LG4 305 V8
Hooker 2055s with y-pipe
No other exhaust components welded up as of yet

The problem is after putting these headers on, the car likes to backfire a lot out of the open y-pipe at idle (although it doesn't do it when cruising or at WOT), and my gas milage is terrible. I went through a 1/2 tank of gas just flooring it around town like five times.

My friend keeps insisting that it is because the rest of the exhaust has not been connected yet (a Catco cat and Hooker catback are both going on in a week) and "lack of backpressure" is causing it, which sounds like BS to me. However, there is a tiny hole where my friend cut off the air tubes and welded them shut again. It is on the driver's side header where the O2 sensor is located and is about the size of a needle (pinhole). I'm not sure if that might be affecting anything or not.

Basically, I just want to know what would cause a backfiring after installing headers and what to do to fix it. I would also like to know if this has any correlation with the bad gas milage.

Thanks,

Nate

 

The backfiring definately has something to do with your bad fuel economy. Backfire is often the result of a severely wrong air/fuel mixture. I had backfire happen to me when two of my injectors went bad. Your situation may be due to your o2 sensor being near regular air. Thats just a guess though. Connect the rest of your exhaust and try it then and let us know.

 

I could see that being a possibility if I were just running open headers, but the y-pipe is fully connected. Is that still a short enough distant for outside air to reach the 02 sensor?

 

plus wires on incorrectly???

 

Most common reason for backfiring/running rough, etc. after a header install...... burned a plug wire or boot against a header tube. Or you got the plug wires on the wrong plugs but then it would run with a dead miss all the time.

With computer controlled engines (like your LG-4) you also need to make sure you have the O2 sensor installed and hooked up (and that it's wires haven't burt against the header either).

 

I was thinking the same thing initially, but he said that it only ran rough and backfired at idle. That leads me to believe its something to do with the o2. If it is running worse at all RPM, then I would agree 100% with a burnt wire or crossed wires.

 

It doesn't really run rough at all, but I can definately hear what sounds like a small backfiring when it idles.

I'll go check the plugs wires today to make sure there aren't any crossed wires. The O2 sensor has been working properly and isn't burnt on the header (made sure it was out of the way of the header tube).

Thanks for the advice.

 

You will need to change the O2 to a 3 wire heated. The standard 02 just does not heat up enough to work efficiently.