starts good when goes WOT then AFR goes lean quickly please help
I am helping a friend with his swap into his 68 Camaro. The computer is from a camaro 5.7 T56, he has swapped for a 6.0 still the manual tranny. We chased around the VE tables and they ended up much higher than I had seen but I am new at this. we have the MAF shut off for now and have not had much time to tweak out the ve tables but it seems drivable for now.
However if you look at this scan data you can see at about 4000 rpms it all the sudden goes lean. It looks like the commanded is still good, there is plenty of fuel in teh tank but I wonder if his pump is up to the task it is an external. The only fuel pressure gage is at idle and it is good so none is mounted to watch during the runs.
Could you look over the tune, and log I dont see anything that should cause this in it.
thanks
Dave
just to add to this he is running the stock ls1 intake which is returnless so he has a corvette regulator right at his pump and tank and stock injectors. I have not changed any of this info.
I also noticed when looking at another log from that day that it is not just rpm but it seems to be consistant to stop the injector pulse at 19.5 msec. The duty cycle is below 80 %.
Awesome thanks for the info I am not sure I would have ever found that. I guess when I turned the MAF back on it would have worked? Anyway I will try this tonight and report back.
Thanks
Dave
well that did not seem to help. I dont have any good logs to add but can work to get some if that will help. I am still concerned he may be running out of fuel weither it is a fuel pump or his lines. This is a returnless system.
I really want to rule out any tune issues but sure am at a loss. I may back all the way into an old tune. The main differences is the VE table. This new one sure seems high compared to what I have seen but it seems happy.
should I renable the MAF?
yea that is probably next, atleast we have a wideband so as soon as it starts going lean we know... But yes I hate for my buddies 6.0 to pop.
we are trying to get ready for the power tour so it seems like it it is crunch time.
On mine i have the power enrich tables map,map hyst and rpm all set to 0. I read somewhere you may need to do that or it might not go into power enrich.Under engine cutoff your fuel cutoff rpm vs gear is on the low side. Here is my tune 5.3 in a 1992 chevy pickup. A lunati 212/218 cam, LT headers and CAI .Truck is a 5 speed manual but pcm is a automatic.Truck runs and drives great.
Thanks for that. Looking at the tune it is commanding a certain fuel ratio showing it is in PE mode so it seems or appears to be sending it more fuel. That is why I seem to keep thinking an external fueling issue.
You are correct we did lower the fuel cutoff or rev limiter and will go ahead and bump that back up some, The cutoff we are seeing happened at 4000 RPM and it did not act like the limiter we just started good on AFR when in PE mode the it just started dropping (leaning) the AFR while below those numbers.
I think I will start over with the original tune. I thought it was the same however I had to change the VE table extensively. I am going back at it again tonight and we will get it...
Sorry guys I got caught away from my computer over the holiday weekend.
We had a couple issues after sorting thru all the stuff. First off I do believe his MAF is bad it would swing the fuel trims way off when plugged in so we took it out of the equation. As we watched what he was doing when it went "lean" there were no other indicators it had a problem all seemed ok even the narrow band o2 sensors were reading high like expected. We swapped my wideband sensor to his gage and as expected that was it. It started working as expected. Thanks all for your help.
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