Sound like fuel, ignition, or ??

[EdNerd]

It rarely gets what you'd call cold in this SW corner of AZ, but I guess my car thinks different. The lows are in the mid-40s. When I first start the car - especially first thing in the early morning but also after setting and getting back to engine-cold - the engine fires up, hits a high idle of about 1200, and then eventually settles down to idle at about 700 or so. This is a 2007 Aveo LE with 107k miles.

As soon as I put it in gear, it stumbles. If I can go forward, I can feather or pump the accelerator and the engine will catch and run okay - no stalling at stop signs or such. If I'm backing up, though - like out of my driveway to go to work - it almost immediately stalls. I'm thinking perhaps because I can't give it the same acceleration as I can going forward and still control the car.

I've had a check engine light for some time, and noticed no ill effects on the engine running. My normal commute is about 40 minutes up the highway to work and then back - no problems there. I did just recently take a much longer trip - the first one: about 3 hours up, driving around the Big City on freeways, and then coming back. (I usually get a rental, but I wanted to see how the car ran, and I have AAA!!)

I know I'm due for the next oil change. I've never changed the transmission fluid. I did plugs and wires when I did the timing belt at 85k (just after buying the car). I've occasionally - but rarely - heard a few "puff puff" noises - not pinging, but maybe missed ignition firings??

First thing I know is to clear the CEL code and get it checked again if/when it comes back. Is it possible this is just condensation in the fuel tank? Clogged filter? Or pump going bad? Just time for another set of plugs? Or maybe something more insidious and expensive??

How would you go about troubleshooting this?
Ed

[avguy]

I .... First thing I know is to clear the CEL code and get it checked again if/when it comes back. ...

Actually, the first thing to do is read the code(s) prior to clearing them, and evaluate them in the order they appear.

.... How would you go about troubleshooting this?

You need to keep in mind that the symptoms you're describing could be caused by MANY things, and that guesswork and throwing parts is not the way to go. Best by far is to diagnose by using a realtime data stream OBD reader, such as Android with the Torque app, or an off-the-shelf reader. Data parm values, such as fuel trims, Map sensor, ECT sensor, etc can be extremely helpful in diagnosing, and sometimes may even identify the exact problem. A multi-meter is frequently needed for the diagnostic process as well.

[EdNerd]

So sorry for the long delay - I misplaced my code reader. Finally found it, and had time to do this.
The codes in order are:
P0172 -- System too rich (Bank 1)
P2188 -- System too rich at idle (Bank 1)
P0131 -- O2 sensor circuit low voltage (Bank 1 Sensor 1)
P0172 again
P2188 again

The weather seems to have warmed up slightly. The CEL went off for a while, but now it's back on. I also read somewhere on the forum the advice to turn the key to ON a time or two before starting - and when I heard the fuel pump going, it made sense!

The car is no longer stumbling and stalling in reverse. It seems to have an initial high idle of about 2000 RPM, quickly dropping to around 1200-1500. Even with the CEL on now and the car at dead-cold first start, I'm not having the stalling issues.

So I'll clear the codes and see what pops back up as I drive this week. If anything does, I'll note it, and perhaps see if I can take a drive with the code reader displaying real-time data. Not sure what I'd see, but maybe something important(?).

Ed

[avguy]

... and perhaps see if I can take a drive with the code reader displaying real-time data. ...

Not sure if we're talking about the same thing, so I'll ask if you have something beyond a basic code reader. A realtime data stream reader reads and displays OBD data values such as fuel trim, throttle position, MAP sensor value, and many others as well. Is that what you have?

[EdNerd]

I have this one: Memo U581 Scanner Live Data OBD2 Code Reader CAN OBDII EOBDII Diagnostic Scan Tool Support Multiple Language with CD
It does have a "live read" function on it., and I have used it while driving (different car).
I will not guarantee that I knew what I was looking at on the screen, however!

Ed

[avguy]

The tool you have is just a code reader, and does not read the OBD data stream. In the absence of the data reader, about all I can suggest is to replace the upstream O2 sensor. I don't normally recommend hanging parts, but without diagnostic tools, that's about all you can do.

[sparky34kv]

You're describing issues with the fuel and igniting but not anything about normal maintenance other than your timing belt and transmission fluid. I would start with the basics, check or replace plugs, change fuel filter and maybe even run fuel system cleaner through a tank of gas. I know the dealer recommended a fuel system cleaning when I took it in during normal warranty routine maintenance. I have run Seafoam through it once. When was the last time the air filter was replaced? Just looking at the simplest things having to do with the air and fuel to the engine, as well as spark. Once the basic components are known good, go from there.

[EdNerd]

Again apologies for the delay in responding - obnoxious work schedule ( 11-12 hrs/day, 6 days/week - hard enough to find time to sleep, much less work on the car!!)

Gonna try to get the plugs replaced this weekend. Maybe the wires too.
I'm also due for an oil change. Just gotta find a place that's still open when I come in from work.

New wrinkle: lately the engine has been surging. While driving, at moderate to heavy acceleration, it will balk and buck a bit. At a stop sign, the engine will falter and the lights dim, then surge up to about 1500 rpm, and see-saw like that until I take off. If I hold the accelerator at about 1100-1200 rpm (in gear with foot on brake), it doesn't surge. The check engine light will be off, blinking, or on - no rhyme or reason that I can see.

Ed

[petrified.rabbit]

A blinking check engine light is sign of misfire. Most manufacturers suggest shutting the car off immediately for a blinking CEL.

From the sound of all the things going on in this thread. and the codes you did have, I would have to agree with AVguy and suggest trying to replace the primary O2 sensor. I would hate to put it on, but it is the most likely solution other than a clogged injector or a misfiring cylinder. However a misfire would rob you of power and not allow you to "Fix" the issue by holding throttle higher. An o2 would allow this as some extent.

Another possibility is a leak in the intake tubing, or a sticking throttle body. Those are sort of easy to check, so I would look into those as well.

[EdNerd]

Well ain't this a fine kick in the pants!!

I changed the spark plugs (same kind as I had - AC Delco 41-602) and the air filter. The plugs didn't look bad at all.

I did have to pull off all the plug wires, but they all went back in the right place.
Along the way, I did notice what might be a cracked vacuum line:

Put the cover back on the engine and started it up.
It immediately started surging, going from 500 to 1500 rpm and back down.
I put it in gear, backed out of the driveway, and drove off, figuring it would settle down.
Nope - went into limp mode!! No flashing CEL, but no more than 10 mile an hour!!

Just the spark plugs!! I didn't touch nuttin' else!!
Maybe the wires got jostled on that plug left center of the engine cover??
Tomorrow after work I'll pull off the plug wires and reseat them.
And I'll check for new codes and clear them.
If nothing becomes obvious, I may have to tow it to a mechanic!!

Ed