Help me trouble shoot..

[AveoChick]

Okay, I'll try to make this short sweet and simple. For reference I work on my own car as much as humanly possible.

Started car one day, packed it up for a trip, the AC was on, and suddenly it stalled out. Started right back up no problem, then stalled out again.
I immediately replaced the camshaft and crankshaft position sensors, because I know that those can be an issue.
This did not help the issue, but I finally got a CEL code. The code stated that the RPMs were not high enough. I googled it, easy enough, I replace the throttle body which contained the new intake air control valve. I did an idle relearn on it.
It continues to stall at idle. I have a new O2 sensor upstream and downstream, but I am receiving check engine light codes for both O2 sensors, as well as running too lean.

I am thinking vacuum leak, but the brake cleaner spray trick did not produce any effects that would lead me to the leak area..

**Once I'm going on the highway, I could drive 10 hours and not have a single problem, which I did because I had to go to Tennessee for work.

**My valve cover gasket has needed replacement for a bit now, is it possible that the issue could be related to the PCV valve and I should just change the valve cover when I replace the gasket?

Any ideas would be helpful.

[Eg.h2o]

**My valve cover gasket has needed replacement for a bit now, is it possible that the issue could be related to the PCV valve and I should just change the valve cover when I replace the gasket?

Any ideas would be helpful.

I'm thinking the same thing. Yes to new valve cover and gasket. Also replace the vacuum hoses as well if possible. They are after all, old too.
perfect time to change old spark plugs too.

[AveoChick]

New spark plugs last month
Will change vacuum hoses also for good measure.

[Arrakark]

Here are my thoughts:
An engine needs four things generally: fuel, air, spark, and compression.

Immediately, I'm thinking it's not a spark issue because as you stated, once you get it going it runs just fine. Also, replacing the spark plugs means that the only parts left that are undiagnosed in that system are the spark plug wires and the coils. You can rule those out by pulling the fuel pump fuse, burning up the gasoline in the fuel line by cranking for 5 seconds three times, then grounding one spark plug at a time and cranking the engine to see if you get a spark. It's also my opinion that maybe if this is a spark problem it may be caused by a weak spark, but that will show up as a rough idle or generally rough running engine.

In terms of air, you need to make sure that you have good air coming into the engine. I would start by checking the simplest things (if not done already). I'd start by checking the condition of the air filter and air cleaner hose (lots of rips in the bend in the hose can cause this). A vacuum leak will stall an engine if it's large enough. However, in my experience you need to have a very large leak before you stall an engine, and at that point the leak will be so large you'll spot it very easily just by hearing it. I accidently induced an engine-stalling vacuum leak by not seating the injectors properly, and I could hear the leak all the way from the driver's seat.

If your car isn't super high-mileage, then I think this is most likely a problem with the fuel. Low fuel pressure may cause this. How does the car sound when you turn the key right before crank? Can you hear the pump? If so, does it sound alright? Generally, the pumps have an all-or-nothing failure mode. But low fuel pressure can be caused by a clogged or dirty fuel filter. I'm thinking it's not the injectors because you will probably notice a misfire in that case. You can confirm this via the spark plugs. If you take out the spark plugs, how do they look? If they are not uniform in color/charring you may have an injector problem. Depending on your model year you may have a secondary filter (primary is in the pump in the tank) around your gas tank near the rear which is replacable and pretty cheap. If not, you may be out of luck.

Lastly, if it's a super old car the piston rings and/or valves may just be worn out. A compression test will verify. Can be done pretty cheap with a meter.

If you suspect the PCV valve, I would take it out, see if it rattles if you shake it, and clean it. Although generally symptoms of a bad valve are gasoline and gasoline smell from dipstick, plus dirty oil.

The O2 sensor codes may not be real BTW; as in they are simply a symptom of another issue. I had a fuel-rich condition where the upstream sensor code went off for low-voltage. Turns out the sensor was fine and it was the rich condition that was causing the code. It could be possible that your O2 sensors are acting up simply because your engine is running really lean.

I don't really see how a valve cover gasket can cause this. I had a leaky valve cover gasket and the first thing I noticed was the ridiculous amounts of oil leaking out lol. I also think that the sensors (at least the camshaft one) would certainly throw a seperate error code if they were bad.

Also, sounds like you have access to a OBD scanner. What are your fuel trims at?

Hope you can sort this out!

[AveoChick]

2010 Chevy Aveo 123,000 miles.. Run Mobile 1 full synthetic since day 1. New air filter per the book..I maintain my cars like GOLD. My 94 Corolla made it to 305 k. Compression is good.
I have a newer hose from air filter to throttle body due to noticing a crack when I replaced the filter back 2 years ago.

Spark Plugs are newer, replaced them 11 months ago along with coil pack. I did this when I hit 115k miles. Sparkies needed replacement anyway..

My 2010 Chevy Aveo has PCV built into valve cover, so to replace it means replace valve cover in order to replace PCV valve.

My fuel filter and fuel pump are integrated and easily enough fixed. I will look at fuel trim

[Eg.h2o]

Fuel trim can be affected by a blown PCV.

[AveoChick]

Very true. I am off in RENO for work, BUT when I arrive back home I am going to replace the PCV valve and gasket.

[Hoosiertrucker]

**My valve cover gasket has needed replacement for a bit now, is it possible that the issue could be related to the PCV valve and I should just change the valve cover when I replace the gasket?

I have a 2005 Aveo, and I've read on here many times that when the valve cover gasket o-rings around the spark plugs go bad, they tend to pool oil in the spark plug wells, fouling the plugs. I'm not sure if this pertains to your 2010, but it's worth pulling some, or all of the plugs and at the least checking them. Stands to reason that if they are oil fouled, they would not produce enough spark at lower rpms to initiate combustion, and could be flooding the car out. Hope this helps!

[AveoChick]

Thank you!! I am picking up a new set of sparkies and will try that.

[Hoosiertrucker]

Actually, the o-rings that go bad are rubber ones, that are a part of the valve cover gasket set.