Flat lines during deceleration

[SlowButFast]

I have a 99 grand am gt w/ swapped 3.5L engine. My car is doing what I can only describe as flat lining when I decelerate(mainly from highway speeds). I can be doing about 34mph, decelerate and the engine stumbles dropping to 600rpm for about one second. During flat line fuel trims run 0.0, my wideband goes 22.0, and injector pulse zeroes out too. I've had this problem for a while now, but I have attempted fixing the problem before. In my attached scan you can find it right after the 6600 frames, then I flick the pedal to make it respond again.

P.S. How should I adjust for KR with a limited parameter setup like the GA?

Thanks for checking this out

[vortec]

DFCO (Deceleration Fuel Cutoff)

[Perforator]

You get KR during deceleration?

[MMGT1]

Are you running a 3500 PCM? Have you put the tune "back to stock" to see if this still happens? You have one of two things here, bad MAF or bad PCM. I am in the middle of dealing with the same issue. My new PCM was ordered on the 10th, waiting for it to come in. Mine did this 4 years ago and I tried everything, when I would put it to a previous tune it would be fine for a while and then it would eventually start to act up again. I replaced wiring harness, MAP sensor, MAF sensor and nothing was "fixing" the problem. Then I replaced the PCM and have had 4 years of tuning bliss, until 3 weeks ago when it did this again. Your scan looks all to familiar to me bud. I can't say 100% that it is your issue, but if I was a bettin' man.... catch my drift??

[SlowButFast]

@vortec
I don't have DFCO parameters. . .. v6 blah blah. . .

@ Perforator
KR was at 100% throttle, that was a completely separate question

@MMGT1
I get what your saying, but its the same old pcm since 99'

[Perforator]

Gotha. The flat lining is not a problem. That's normal. It's deceleration enleanment or deceleration fuel cutoff.

[SlowButFast]

Gotha. The flat lining is not a problem. That's normal. It's deceleration enleanment or deceleration fuel cutoff.

Ok, I have deceleration enleanment but didn't know if it was worth adjusting. If you care to look its under Fueling > Accel Enrich

[oakleafresin]

What they said ^^ DFCO. Deceleration enleanment simply lowers the IPW while decelerating so that the car uses less fuel. DFCO sets the IPWs and spark to zero so that the car can use the engine to brake.

[SlowButFast]

Well damn, I think I just learned something new haha. Thanks

[MMGT1]

Hey guys, look at what his trims are doing before at highway speed. No difference in timing, airflow, spark... anything but his trims start to go nuts. I would bet within a couple of weeks he begins to have stalling issues when coming to a stop from highway speeds and having to "two foot" the car to keep it running. Just something to look out for, if it starts happening like I have explained, PCM needs to go.
What I see his trims doing at cruse is all too familiar is all. Hopefully it does not do this, but if it does....

[bilemke]

Hmm. Fuel trims look like other 3400 grand ams I have scanned. LTFT is fairly costant, STFT is rapidly changing but not by that much.