DE issues maybe

[91chevZ71]

So when I'm coasting down the hill at 45-50 MPH, my RPM's are at 1500 and stable (no surging). When I'm going 55-65, the engine surges and it feels like I'm hitting a wall then going, slowing down real fast, going, etc. THe RPMS jump up and down about 400 rpm when this happens. THis is all coasting (coming down on I-70 into Denver from the mountains) with no throttle in. I know I'm spiking lean when this happens.
Is this a DE issue or something else?

MIke

[davo727]

Sorry cant help, we dont have hills here to coast down :) Dave

[91chevZ71]

yeah, texas is pretty flat. hot as hell I bet

[davo727]

This part is flat as a board. There are hilly parts of texas though. This summer had been a lot cooler than normal but it has rained about 45 out of the last 60 days.

[91chevZ71]

Yeah, it's been raining a lot up here. Truck runs better...can't complain about cold air!

-I think I'm just running lean in those areas, enrichened the low map VE by 5 percent. worth a shot

[YenkoST]

Mess with the timing a little on closed throttle vs. RPMs. If its not that, then move on to fueling.

[91chevZ71]

I don't have the 7747, just received the Flash EBL. I think it's a fuel issue, my pw's go to zero then fire then zero etc.

[YenkoST]

Ah ok.....how about the main timing table at about 20/30 kpa...increase it a little at that rpm range and see what happens.

[91chevZ71]

sounds good. thanks again yenko

[YenkoST]

Not a problem....LMK and we will try some more stuff. Just increase it 1-2 degrees and decrease it. Then if that doesn't work, adjust the VE table in that area accordingly.....more fuel.

[91chevZ71]

hey yenko look at this and tell me what you think
http://i184.photobucket.com/albums/x246/bmd2_colo/lowSA.jpg

[YenkoST]

Well, I'll tell you what I think/do:
On mine, I have from 20-40kpa from 3200 and above about 40* timing. And I would say about 1800 rpms to 3200, increase the 20-30 about 2*. As much as 35* can be done with 93 octane.

You have load of timing at idle too. You try lowering it some to about 22* about the 40kpa marker if you want too.

[91chevZ71]

I thought the same thing with the idle SA, but every time I lower it the motor gets rough. It barely idles at 20 deg!! I will reduce 1 or 1.5 and see what happens, though. 18 Deg at idle gets me the mother of all surges (in Drive)

[YenkoST]

Well, I have heard that the 212/222 in the 330HO engine needs a lot of timing at idle but durn.