Hey all. The 08 LT 2.4 was running rough. I had the code for a faulty exhaust VVT solenoid and faulty MAF sensor, so I went ahead and replaced both solenoids thanks to the helpful tutorial here, and replaced the MAF sensor. I also replaced the air filter (it was filthy) and looked at the throttle body opening while I was there. Very little carbon build up, but I sprayed some throttle body cleaner on a soft brush and cleaned it up, pressed open the butterfly valve a bit and cleaned the edges around it. I put everything back together, reconnected the battery, and started it up.
​​​​​​The good news is that it started up. Ran smooth for a few minutes, then started running rough again.
Drove it to the grocery store and got a new CEL. Connected the scanner and got a P0172 - fuel trim system rich.
Then it died at a stoplight. Thankfully started up again.
Got home and did the throttle body relearn. Disconnected the battery for 30 minutes. Started it up and idled for 3 minutes. Off for 1 minute. Idle for 3 minutes. Off for 1 minute. Rescanned and got the same P0172 code.
Live data showed short term fuel trim. bank 1 sensor at - 9.37% and bank 2 at 99. 2%


Any ideas what my next step should be? I'm tempted to put the old MAF sensor back in.
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Precisely, what were those codes prior to the repairs. The numbers not the descriptions?

How many miles on the car?

The P0172 does not correlate well to the stalling. P0172 alone basically says the ECM is correcting for an initial rich condition just fine, but It just thinks the correction required is excessive.

I'm not an expert on this, but my guess is either you'll get more codes, or the car will correct itself with a better initial a/f on startup and the code will go away.

I kind of doubt the latter because of the stalling. Clogged fuel injectors can lead to uneven a/f in the cylinders, causing the ECM to unsuccessfully hunt for a good a/f. Or there could be something wrong with the #1 O² sensor.

There is no Bank 2 O² sensor because there is no bank 2. You're probably talking about the #2 (downstream) O² sensor. Don't worry about that one for now.

 

Thanks for the quick reply.
215k miles.
P0014 was the VVT code.
Once before I got around to fixing it I also got P0326 knock sensor code.
I believe the MAF code was P0102.

I had the fuel injectors replaced a few months ago. It would often not start cold in the morning. Just acted like an old carbeurated engine getting flooded. The mechanic pulled one of the relays under the hood and his assistant started it right up. Said, "leaky fuel injector. Gas is pooling up overnight and needs to be burned off before it will start."

Haven't had any cold morning start problems since, but I have had three occasions when I went somewhere (store, restaurant) and came back to the car an hour or so later and it would almost start, but then act flooded. I would wait a minute and then try again, giving it a little press on the gas pedal and it will start up.

Meanwhile, the general low end acceleration is pretty bad. Highway driving is fine, but taking off from a red light I have to almost mash the pedal to the floor to get going. (The transmission is fine. A local shop checked it with their scanner because I thought maybe first gear was the problem, and nothing came up. That's why I was hoping the combination of things I did today would help.)

 

This stretched chain caused similar symptoms in my 2.4

 

Interesting. Is there any way to determine this without opening the engine up? I think that is beyond my shadetree mechanic skills.

 

Nope you have to remove the valve cover, not that hard of a job. Even replacing the timing chain is doable!

 

The p0102 usually comes from either forgetting to plug the MAF in or a bad connection at the plug.
And look for air leaks between the MAF and the #1 O2 sensor, particularly around the air horn, the area around the PVC inlet is prone to cacking.

 

Thanks, I'll check that over the weekend.

I'm traveling for business next week, thankfully in a different car. If I don't find anything there, I'll probably take it to a trusted mechanic when I get back and have him check the timing chain.

 

The P0014 did not come back then? That would suggest that the replacement VVT solenoid did the trick.

How confident are you that your mechanic used the correct fuel injectors? If he ordered the ones for a 2009, that would probably cause a P0172.

 

Yes, the P0014 has not returned. So that's the good news.
I assume he got the right injectors. He's pretty good with parts. But it's possible he screwed up. Unfortunately the car is in a different state now, so I'll be taking it to a different mechanic when I get a chance. I'll put it on the list for him to check.