I did a few hours of PW and MAF tuning today and on the way home AFR went to 11.xx and then up to 17.xx. I tried loading a previous tune and nothing changed, still f'd up. I tightened up the supercharger bolts and still no change. What could it be?

 

It's no big deal. The LSJ has a very irradic AFR. And when you decel it cuts fuel off so it jumps to 17+. I wouldn't worry as long as your idle pulses near 14.7 range, and your WOT stays under 11.6

 

Sorry, i didn't explain. Those are the AFR's at idle and cruising...not good.

 

couldnt have said it better myself

 

They seriously fluctuate that badly. Don't stress yourself. Just get that MAF dialed in so that the Scanned MAF table is within a percent or two of the written table. That will just take a little time and driving around. And write them by hand don't copy paste. Just use your best judgement on it (like not copying over erradic data) and if you ever wonder if it's all out of whack just look at the table you wrote as a linear graph and make sure that it still has a nice even upward curve to it, and not all choppy.

 

I really don't think it's MAF considering I've done a few hours (besides today) of MAF tuning. Also, this happened in the middle of tuning, not right after I loaded corrections. I'm thinking maybe something mechanical, but I'm not getting any DTC's. Possibly bypass solenoid?

 

Nope, it's just your Paranoia Speculus acting up. You should probably take a look at that and make sure you don't become a certified member of the "What the **** was that Tuning Club".

I think you are making this into something. I have never seen a Cobalt with a steady AFR on the wideband. If you go put in on a sniffer it will be more steady.

 

It has been fine all day until 1hr ago. My AFR stayed in between 14.50-15.00 all day until this happened. This is not the tune. I've tried 4 different tunes w/ different MAF values and PW adder values and I still get the same thing.

 

its not ur tune,might be ur gauge,or the sensor it self is bad...i have the gm s2 tune and its perfectly fine

 

By the sound of the engine, I think the gauge is right. If you listen closely you can tell when the engine is in a lean condition, like it's trying harder.

update- I just went out and tried again and it's up in the 19.xx's!

C'mon fellas I need a little help here.

 

Clogged injectors?

 

well when my car was at the shop couple months back,they told me i was running lean at idle...they changed the following and one of them helped

1.o2 sensor
2.gas cap
3.spark plugs
4.cleaned injectors/flushed/unclogg

 

I'll go check

It acts different every time I turn it on... I'm going to recalibrate the AFR sensor tommorow

 

Your wideband reads into the 19's? I think the ones I used only went 17 something.

You've got to be having a problem if you can hear the car leaning out. What setupa re you running? Pulley? Injectors? Downpipe?

 

60's, 2.8, ported head, + more...

 

Wow, the ported head is unnecessary.

 

^^^ What? More Cfm's @ less boost =HP

 

The cost of a ported head vs. the gains............completely unnecessary.
we only used the ported heads on the turbo cobalt, and that was to rev to 8k rpms. It didn't even need a porting running the 24psi, we planned on using 28psi so we ported and put in some other work.

 

IVT is playing with you

 

Pscho-I ported the head and went with larger valves so I could flow more air and not stress the blower into making insane IAT2's. Overall a safer engine.
Area WTF is IVT??

 

the intermediate value theorem???
lol sorry math nerdiness coming out...

 

Ok... so I've cleaned the MAF and recalibrated the wideband. When I first turn the car on I'm near 14.7 then once I start driving I start commanding crazy #'s like 14.3 and 10.1 and I'm reading in between 12.xx and 17.xx!? This makes MAF tuning impossible. I have tried setting up user defined PID to read manfold vacuum, but all it reads is zero. Is my computer telling me to **** off is there something else going on here?

 

intake valve temperature.

 

Have you checked your fuses? Usually when a sensor reads 0 its either unplugged or the fuse it connects to is blown.

 

Yeah I checked the fuse, I may need to get a new vac system