Greetings All!

Found lots of help here with my last posts, here we go again.
2009 Cobalt LT 2.2L 219,000 Miles

Just had a Check Engine Light come on today and it's 3 codes

• P0102 Mass Air Flow
• P0171 System Too Lean (Bank 1)
• P0300 Multiple Miss Fire

I am going to - Clean the MAF Sensor, Wash/Re-Oil K&N and maybe do some SeaFoam & Check around for any vacuum leaks.

Any Suggestions to keep it out of the shop? Any of the above not recommended?

Would love to hear the opinions of those who are knowledgeable!

Maintenance Insight, Oil Change Every 15,000 - Amsoil 5w-30, Spark Plugs last changed at 200,000 NGK Iridium IX Spark Plugs , Last Oil Change about 1000 miles ago, Did SeaFoam Then (was pretty dirty) CEL Came on, then went off for about a week.

 

I would just replace the Mass Airflow sensor. The sensor basically regulates how much air goes into the cylinder. Since you have a System Too Lean code, the airflow is being reduced which in turn is telling the computer to hold back on the amount of fuel being injected into the cylinder in order to keep the correct fuel/air ratio.

Replace the sensor and all three codes should go away.

 

Only that first part is correct

The MAF measures how much air is flowing in, not regulates it. That's the TB's job. Lean code means there's TOO MUCH air, not too little. Which could be the result of a failing injector/fuel pump not supplying enough fuel, or a leak in the airflow piping after the sensor allowing un-metered air in, or simply a bad sensor reading false amounts. Since you also have the P0102 maf low input code, it's possible it's a bad sensor or a large leak, as a fuel problem won't cause that code.

The P0300 and P0171 are resulting from the P0102, so address that one. You can clean/investigate the MAF, but i'd wager if it's just a MAF problem it's beyond cleaning. They do fail from time to time.

Check your PCV/evap lines around the TB and on the intake tract, make sure everything is plugged in/sealed properly and in good shape, no hoses cracking or brittle that could be allowing a leak. Listen for any hissing sounds of air being sucked into the manifold past a gasket, but in this case the P0102 is indicative of a rather large leak.

If all looks good, I would just go get another MAF for it. Install that in the proper direction, clear your codes and see how it runs. Let me know what you get.

 

Thanks Joe & Lotus, It's worth mentioning that the Check Engine Light came on yesterday, and went off, and today after this post I drove down to the parts store for SeaFoam and when I cranked up leaving their parking lot it was OFF again... I have a flowmaster exhaust and K&N Air Intake so "listening carefully" may not be happening lol, but since you say that code would be for a large leak I am going to inspect all the vacuum hoses. What about the one that goes from the....evap purge solenoid (replaced that once before!) to the intake manifold its supposed to be "harder" right? its smooth shiny I guess plastic or something but the rest are rubbery softer hoses. That one has kind of a snap or clip attachment. I do disconnect that one (at the purge solenoid) for seafoam or the brake booster line but I find the one from the Purge Solenoid to the Intake Manifold is easier to reach. I guess i'm gonna have to keep an eye on this since it comes and goes...at this point daily. Still gonna clean the sensor just in case because I did notice there is a puddle of goo at the bottom edge of my K&N filter trapped between the dry charger so maybe some filter oil/water/gooey mix got on there i'll have to see what the inside of the air intake tube looks like

ACDelco 213-4222 OE Service Mass Air Flow Sensor if I need to replace correct?

JET 69143 Powr-Flo Mass Air Sensor by Jet ---- Waste of time & Money? (i've read a few posts - cant decide - my car IS Tuned, HP Tuners)

 

About to go to a call for work so I'll be driving about 50-60 miles round trip. Ill see how it drives and post what happens.

 

Yeah I derped I meant it reads the air going through.

And I wouldn't think a lean code would be a result of too much air because the reduction of air going through the intake would cause the fuel to be reduced as well to keep a balanced mixture of air and fuel. If you unbalance the mixture you'd either starve the engine of fuel or flood it completely.

Maybe I'm thinking fuel where I should be thinking air. I don't know. But in either case I would think a new MAF would fix the issue.

 

It's lean because the O2 sensor is reporting not enough fuel coming through to burn all the air. This is happening because some of the air going through the engine is not being seen by the MAF, so there's no fuel being added.

Say the engine is only receiving 85% of it's air through the normal intake, the rest though a leak or something. The PCM 'knows' it should be getting approximately a given amount of air for a certain RPM and MAP value via the VE table, and if it doesn't match up to the MAF readings then it will set that code saying the MAF value is low or high or whatever. This is why the MAF low input sets, and the result is a 15% air charge that isn't having fuel sprayed in to burn up. You get oxygen left over in the exhaust or very lean burns which the O2 sensor picks up and sets the 171 code.

The actual reason the 171 trips is because the engine is adding fuel via fuel trims to reach a happy medium, and it's over 20-25% added to reach stoich or it can't reach it. The car will tolerate a fairly decent amount of fuel trims before setting the code in reality.

 

Ok everything SEEMS smooth after the SeaFoam...drove about 50 miles round trip as i mentioned before, it seemed to be doing ok... but like I said this comes and goes, so i may be back on here tomorrow night saying it started again...but before at redlights and longer stops it would..i dont know if shudder or what is the right word, think of maybe a bass "wave" it would be a small rough idle, that grew and then subsided, at times sounded like it was almost sputtering - probably not the right word, but not a smooth exhaust note at idle. Now it's smoothed out and not doing that....for now?

when I got home I took apart some stuff :
I did not see any evidence of K&N Filter Oil going through to or accross the MAF sensor - wiped inside the Tube behind the filter, saw nothing on the rag - I did find something interesting from "that hose" that connects to my K&N CAI Tube, (Oil Vapor something....port?)

See pic below. As a result the Throttle body was kinda dirty....nothing bad considering its been 10,000 miles at least since i cleaned it. Cleaned it any way, now its shiny

My Air Filter is still Red not grayed out with dirt and dust...so that should be breathing fine. I cleaned off the MAF sensor with the spray just to be safe.

 

That tube is the PCV and it's designed to vent crankcase vapors back into the engine where they burn up an don't create emissions. So oil there is normal. You can add a catch can in the line to cut down on the oil buildup if you wanted.

 

That makes me feel a lot better lol