2.3L Engine Problems

[Guitar's Cry]

Hi all!

I have a '95 Grand Am SE with a 2.3L Quad 4 engine. It's used (135k miles), and since I've got it I've had issues with it stumbling on acceleration when it's at operating temperature and has been turned on and off a couple of times (y'know, shopping and all!). It would die when in idle or when giving it some gas, then wouldn't start until it had sat for a half-hour.

It set trouble code 44 for lean exhaust.

I checked fuel pressure, and replaced the fuel pressure regulator (last week). That solved the stalling and stumbling problem, but the engine still ran fairly rough, and it took a few key turns to start.

A diagnostic tool showed me that the 02 sensor was running badly. I replaced that yesterday and ran fine all day. This morning, it was hard to start, and died in idle. Giving it some gas seemed to help, but then it surged a bit in drive (with brake), and stumbled on acceleration. After getting it on the road, it seemed to run fine, but turning it on again later it would stumble again, and the engine ran wicked rough. Getting it on the road, it ran fine after a while.

I'm currently getting no trouble codes, and the diagnostic tool is showing the 02 sensor as running fine (though, the fuel is rich on start up.)

I've exhausted my automotive knowledge, and my repair manual has met my wall numerous times already. Anyone have any suggestions? Is it as simple (heh!) as a clogged cat? My injectors seem to be running fine, my plugs look good, my fuel pump and filter are new.

What am I missing?

[xeroinfinity]

Welcome to AF !!

Have you checked the IAC ?
Any vacum leaks ?

Also you injectors could be working, though they still could be weak or worn out or clogged, this can cause it to run rich.