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Recently did a cam swap on my 6.2 ls. I have the car running great in maf only open loop but if I re-enable closed loop maf only the car runs like crap in the cruise areas. fuel trims are mirroring what my wide band is saying. I don't understand stand what is going on here. with the closed loop back on its surging and almost sounds like its cutting fuel at times but cant see anything on the scanner showing that. Im about to give up and just pay someone to do it lol. is there any harm in just leaving it in open loop its not a daily driven car.
is the commanded AFR the same in open loop as closed loop? And its meeting the commanded fuel ratio? if cruise is at lowish rpm you may need to increase fuel with a high overlap cam.
yes its commanding the same afr in both. when its in open loop it is almost a perfect match. in closed loop once its starts switching the 02s is when it acts up ive even lowered the proportional fueling cause it was swinging pretty wildly.The surge will happen in the lower rpm range off idle to around 2500 ish. i did notice at idle if i get it rich enough i can almost make the cam lope completely smooth so i think your on to something there with increasing the fuel down low. just been bangging my head off a wall when it goes from running great to pertty bad in one flash and not changing much. Sometimes two brains are better than one.
It could be the O2 going bad, when I see the trims going from -20 to +20 I usually swap it right away.
That is if you know the MAF curve is properly tuned and that you have good injector data.
maf curve is good injectors are stock and trims are no where near +-20 more like +-5 this is why I'm confused. when i say it was switching wildly I ment extreamly fast compared to othe engines ive tuned.
Ok I see, the cam overlap can skew the 02 readings quite a bit but to help you diagnose the issue I would try to operate the engine in an area where you won’t see the overlap affecting your sensor and look at the trims what they are doing.
In my opinion, +-5 shouldn’t make the car drive like shit though. What is going on with fuel pressure at this point in the tune ?
its only doing it in the low rps anything above 2500 rpm or of its forced open loop it runs great
yea you might lower the gain to slow down the O2 reaction so its around 1 cycle per second or so and richen the commanded mixture to 13.5 -14 afr and see what it does. wild swings can go lean and give trouble.
thank you for giving me some direction to go on was getting a little lost and just stopped before I screwed it up completely. I will give thoes suggestions a shot and see how she does.