[ccm302]

I had a DPFE go bad on a Lightning I had. When it started going bad, the stuttering got so bad that I either had to be constantly accelerating or decelerating to make it run normally. It only would do it on long trips (most times). Beyond that, I honestly have no idea. I've never had any experience in dealing with the IMRC. O2 sensors (typically) don't make the car stutter (at least no in my experience). I think when an O2 sensor goes bad, the computer reverts to a default/middle of the road signal for the emissions since it can't see the actual reading. That kills your fuel mileage a little because it doesn't try to adjust the air/fuel based on the emissions. Or I could be completely wrong on all of that.

[ccm302]

You ever get it figured out man?

[cobrabro]

Well yes and no. Took it FPS in Marietta, GA and the owner is SCT certified and said that the tune I had from BAMA had 36 degrees of timing down in the lower rpms' which is too much for no irmc's with the tumble ports. He backed it down to 32 and plugged the egr back in. He said the computer is sensing too much timing, backing off and then back on. It definetly improved the stutter / trailer hitching effect but a little still remains. He also expanded on the tune some.
So it's feels pretty good but I am wondering if we should back off on the timing even more although I want to keep as much tourqe as I can for daily driving.
I have heard of other guys running mid 30's of timing with no irmc's but maybe that was not on 98 tumble ports.
Thanks for asking man,