98 Malibu low idle while in gear and intermittent stalling

[MalibuBarbie98]

I have a 98 Malibu 2.4L 4 cylinder that has about 140K miles on her. When it was initially purchased, the idle was pretty good when it was in gear, about 800 rpm's or so. Then one day the oil was changed and from then on it has had a poor idle in gear, about 600 rpms or so and it sometimes feels like it might stall. It has been driven like this for some years, and now when driving and you let the foot off the pedal, it sometime stalls when you are coasting. I've replaced the Idle Air Control valve, but that didn't fix the problem.

I've seen threads where this problem has happened, but I haven't found any thread that has a solution to the problem.

Any help would be appreciated.

We have done zero maintenance on any of the sensors, EGR, Oxygen,...etc.

[tractorboy]

sounds like a vacuum line or the cat is clogged. remove the o2 sensor, see if it is better
is the computer throwing any codes, mil light on

[MalibuBarbie98]

Originally Posted by tractorboy

sounds like a vacuum line or the cat is clogged. remove the o2 sensor, see if it is better
is the computer throwing any codes, mil light on

When you say remove the o2 sensor, do you mean disconnect the wire from the o2 sensor or remove it?

What is the CAT?

I appreciate your responses. This is great info.

[tractorboy]

the 02 sensor , or ox sensor. It is on the exhaust down pipe , in back of the engine on most cars. The cat is the catalytic converter. They can become clogged and will choke off the engine. I just recently learned from another poster that if you unscreww the o2 sensor , it gives the exhaust gasses somewhere to go and the car should not atleast die out while idling. Yes the computer will throw a code. The car should not be driven like that, just for testing. There is a pressure guage that is real cheap you can screw in in place of the o2 sensor that will measure the back pressure for a definative answer. oh btw , make sure the ignition is off when umplugging or plugging back up and the 02 sensor is delicate, do not touch the end and silicone as in silicone spray will destroy it, probably a lot of other cleaners too.
you may also need a special tool to unscrew the 02 sensor, one such tool looks like a spark plug socket with a cut out down one side. of course it could be something entirely different, just one idea.

[MalibuBarbie98]

Originally Posted by tractorboy

the 02 sensor , or ox sensor. It is on the exhaust down pipe , in back of the engine on most cars. The cat is the catalytic converter. They can become clogged and will choke off the engine. I just recently learned from another poster that if you unscreww the o2 sensor , it gives the exhaust gasses somewhere to go and the car should not atleast die out while idling. Yes the computer will throw a code. The car should not be driven like that, just for testing. There is a pressure guage that is real cheap you can screw in in place of the o2 sensor that will measure the back pressure for a definative answer. oh btw , make sure the ignition is off when umplugging or plugging back up and the 02 sensor is delicate, do not touch the end and silicone as in silicone spray will destroy it, probably a lot of other cleaners too.
you may also need a special tool to unscrew the 02 sensor, one such tool looks like a spark plug socket with a cut out down one side. of course it could be something entirely different, just one idea.

Thanks for the info. I just realized after a couple of other threads I saw your responses through what a CAT was. I'll check it out and see what happens.