back pressure

[garunner]

Just a simple question. On a 96 se 2.4, the engine is set up to run with a certain back pressure? I punched out the converter on the car cause it was clogged, Now can this loss of back pressure make the car run odd and lose gas milage?

[Brad97GS]

No, the car should be able to run fine with less backpressure. But if the converter no longer functions, the second O2 sensor may be sensing this and screwing with the fuel/air mixture...

[garunner]

Actually i cleared out the converter cause it was clogged, so it's empty. I replaced the iac yesterday the car idles good and drives good unless you mash the gas and then it sputters a little. so i thought it would be the cat, tps, or ecm. both sensors were replaced already, but that don't means they're bad.Any ideas?

[Jason Lesbirel]

I've found, based on previous experience (with 'Zuki and Honda engines), that on a stock small displacement engine, a big loss of backpressure can cause driveability problems. A cat does create a significant amount of backpressure, and with yours gutted, this could be the root cause of your problems. (Given that you've tested or replaced about everything - including the coils, right?)

If you had a built-up engine, it probably wouldn't be a problem - shop around for a high-flow cat from someone like Magnaflow. They're usually cheaper than factory replacement.

As an aside, I don't know if your state has emissions testing, but I guarantee with a hollow cat you wouldn't pass anywhere.

[Brad97GS]

I drove around without a converter on my Grand Am for 6 months (then sold it) and didn't have a driveability problem. I know of several other Q4 owners with the same results...but I guess I don't know with the 2.4L...

[garunner]

Thanks for the replys. That is the info i've been looking for. I plan on putting a sc on the 2.4

[Jason Lesbirel]

Originally posted by Brad97GS
I drove around without a converter on my Grand Am for 6 months (then sold it) and didn't have a driveability problem. I know of several other Q4 owners with the same results...but I guess I don't know with the 2.4L...

It seems to be more of a problem on cars with copious amounts of emissions-control equipment - My Jetta not only didn't have a cat, but also lacked an oxygen sensor. It started every time I went to her, for 4 an a half years, and I got 28mpg - with a 2.25" exhaust and a large bore TB from an Audi 5000 Turbo. In the city.

If something goes missing, or stops working, it seems to take everything else down with it - Hondas are really bad for that, unless the engine has been modded at least moderately - they're totally gutless without the cat.

[garunner]

That's some good info. I'm tring to get the computer to reset but i haven't drived the pontiac in a couple of days.I just got out of the hospital and can't drive till saturday.so i'll let you know tomorrow on how it runs so far.

[MJE95GAGT]

Sorry to hear that, are you ok now? was it anything bad?

[garunner]

Thank you for asking. I went in for an angiogram to check for heart trouble before i go in for gastric bypass surgery. I finally got the tax return so i can fix my exhaust and see what happens, but if there are any more ideas please let me know. Sorry it's been awhile, my computer took a dump and had to buy a new one.