can somebody please help me with my corvette? Goes really lean under mild thottle +10

[mvvette97]

I have been working on this car all day and have said hell with it for now. It's a 97 vette with LTs no cats LS6 intake descreened Maf and BBK air bridge. During light throttle say 55mph the trims look pretty good but stepping on the pedal to about 1/4 the trims go crazy positive. I have tried several things like playing with the maf and injector flow rate and I can get it so the trims don't go way positive but then idle and cruise trims are pulling fuel like mad. So I put it back the way it was and ran a log. Can somebody take a look and give me some pointers? I just got done tuning my cammed trans am and it runs perfect but yet this mild bolton car is just killing me.

[WeathermanShawn]

mvvette97:

When I responded to your previous thread I did not realize you were showing that much variance to positive on your LTFT's.

I don't know if your de-screened MAF and Air Bridge are adversely effecting your MAF Airflow. I saw some case where your TPS increased, but your MAF Airflow (g/s) actually decreased.:confused:.

I would make sure IPW is back to stock, and in reality you need to apply the attached BENs to Table B5001. If you still have problems after that, you could always experiment with a stock MAF. My first thought would be a bad MAF..

[mvvette97]

oh my other thread was concerning my trans am. I got it all dialed in. This is my bolton vette that is now killing me.

[WeathermanShawn]

Stock Injectors?

The one 'weird' thing about Vettes is Table B3809. (I was re-analyzing your log). The Trim boundaries are so darn close, that you get so many FTC active. You can always log GM.FTC to see what I mean. So if you are at 2201 RPM's and hit the throttle, your MAP goes above 77 kPa..and its the same darn Fuel Trim Cell as 5800 RPM 100% Throttle.

Personally I like the LS1 Boundaries better. I use 2800, 6800, 6801. Less FTC's to worry about.

So, I would still make 100% sure your IFR is matched with your injectors..also make sure you re-set the Trims after a MAF adjustment. On a side note I would keep your PID channels to 24 or less. No screen lag that way.

I also clean the MAF about every 3 months. I went back to a screened MAF myself, but others have no problem de-screened. Its just a thought..

Good luck..

[mvvette97]

thanks Shawn. My injectors are stock and I'm running the stock injector table also. So what would you set B3809 to then? I'll try anything. I'm also going to put another set of MAF ends on that have the screen still.

[WeathermanShawn]

Try the 2002 Camaro values..2500, 6502, 6502. MAP Boundaries can stay the same.

Also, reset those Trims. That +10% in your log looked like a value that is 'stuck' in the +77 MAP kPa boundary from a previous run.

This technique is somewhat of a long-shot. The real secret has to be in your MAF or worst case some fuel pressure problem.

Let us know..

[mvvette97]

Ok I'll give it a try. Oh when resetting the trims does the car need to be idling when I hit the trim reset or just have it connected and the key turned to run? I tried it both ways one day but never did really know if I was getting anything done, haha

[WeathermanShawn]

It should work just with key on (you obviously have to be connected via Scan Tool)

If you Tab under 'Calibration'..'Long Term Fuel Trim Cells', when you hit 'Reset', you should see the LTFT Matrix values all go to zero.

The only other way is a hard reboot..Disconnecting the Battery Power to your vehicle. Not really recommended.