Rich or lean battle

[Frizodanizzo]

I always noticed my sonic ran slightly richer stock, put a cold air on it it runs totally lean high + numbers gray spark plugs. Stock air box - numbers never had codes with these except the lean one p1101 take off the cold air goes away. This was even after the boost sensor, maf, inter cooler piping vacuum lines all brand new. So there's no issues and no codes at all with the stock box but like I said little rich. Just wandering if that is normal used to seeing cars be closer to a very true air fuel ratio.

 

[Stew]

I doubt this would cause enough of a difference to cause what you're seeing but the 2012 Sonics (I'm guessing you have a 2012 from your join date) have the stoich A/F value of 14.7 whereas 2013's and later have a value of 14.12988. The difference is 14.7 is pure gasoline and 14.12988 is E10, which is what 99% of us probably run, so the 2012's would always be slightly correcting for a lean condition unless you actually do run pure gasoline.

 

[spacedout]

I doubt this would cause enough of a difference to cause what you're seeing but the 2012 Sonics (I'm guessing you have a 2012 from your join date) have the stoich A/F value of 14.7 whereas 2013's and later have a value of 14.12988. The difference is 14.7 is pure gasoline and 14.12988 is E10, which is what 99% of us probably run, so the 2012's would always be slightly correcting for a lean condition unless you actually do run pure gasoline.

I had a 2012 cruze before my sonic, after about 2 years of ownership GM did an emissions recall to my car, since that point my 2012 hated the 91 octane no ethanol fuel most of the stations sell in my area. My 2015 Sonic is the same way, cars performance suffers and you can record more knock evens at low RPM high load situations(typically somewhere between 1500RPM and 2200RPM) when running 91 octane with no ethanol. When I say low RPM high load, it could be as simple as pressing down the peddle to accelerate.

I go out of my way to get 93 octane with 10% ethanol, car runs great on that!

 

[Frizodanizzo]

yeah they don't have much choices for gasoline where I live. They rarely have 89 and some reason sell sub regular in a lot of locations 85 octane. Usually you'll see sub regular no ethanol, regular 87 e10, 91 e10 and 91 no ethanol. Once in a while you'll see 89 e10. I think only Sinclair seems to sell it in the area they don't sell sub regular anywhere

 

[Maddmatts]

Extra-low octane fuels are often sold in areas that are at a high altitude and should only be used in naturally aspirated engines.

 

[Frizodanizzo]

Lol maddmatts apparently a lot of naturally aspirated engines aren't even supposed to use it I guess quite a few people contacted the state and they said that their engines blew. The state put out a thing about it plus the pumps say may not be suitable for most vehicles. I don't know how it started becoming a thing because they stated even that it wasn't meant to be put on the main pumps but a separate pump for weed eaters and such. They're finally taking them off slowly but surely.

 

[Frizodanizzo]

What I meant though was with a cold air even a reputable one the car would have a long term fuel trim of +14. With a stock box I've seen as -8 even usually while idling any movement it gets closer to 0 about -1.2 - - 1.8.

 

[Stew]

Have you checked out your intake manifold to see if it's splitting open along the seam where the two halves are electronically welded? There's a thread here about it, several people are having it happen, it can be hard to see just by looking but another symptom would be an intermittent whistle at idle under the hood.

Mine has started splitting and I can see the ECM compensating in the LTFTs. It causes it to be lean at idle under vacuum when it's sucking unmetered air in through the split (which is when it whistles) and rich while under positive manifold pressure as some of the already metered air is escaping out through the split in the seam.

 

[Frizodanizzo]

Crazy I could check but I haven't bothered because chevy just installed it 3 months ago to replace the old manifold. The seal from the pcv line attached to it got sucked out and the turbo was sucking oil through it and blowing a blue cloud like a semi does black smoke lol. Also mine is going in reverse of what yours is doing more rich at idle more normal towards driving around. It was just lean with the cold air on it like drastically lean.

 

[Stew]

Ah, gotcha. Plus if it was just replaced three months ago then I wouldn't think it would fail that quickly.

 

[Frizodanizzo]

Ah, gotcha. Plus if it was just replaced three months ago then I wouldn't think it would fail that quickly.

lol neither would I. Well I was checking it again earlier this time it had premium no ethanol in it, new coil pack and new plugs after a few days of going also. Seems like it stabilized at about -1.6 at idle now. Maybe it was a fluke
It was at -8. It's just odd to me the mpfab intake most people have luck with would make the car run so lean though. ZZP and mpfab claim no tune needed I even tried using the MAF screen even and that seemed to cut it back some. I'm guessing I just need a tune. I guess that's my goal in the next month to use that intake plus it'll save me money during tax time for that upgraded BNR turbo I wanna install. Has anyone on here tried that turbo yet ? If so lemme know how it worked out 20% more CFM over stock definitely sounds like an improvement to me. Especially without ditching my anaconda down/mid pipe at the same time. I didn't get it on sale and paid the extra quick shipping so it set me back a lot. Lol