I'm thinkin I should have left it stock!!!

[tumleweed]

Hi... I have a 95 bbody lt1 transplanted in an 87 Chev crew cab dually along with the 4l60e trans, I freshened it up with a hot cam, 1.6 rr, gasket matched the ports, hooker super comp long tube headers and a tune. It does ok until I let off the gas pedal after a moment of fun and I noticed it bogs for a while when I ease back in the gas, I've done a few EEHack logs and what I see is at 0% tps the timing drops to 1- 9??? degrees of advance and I have seen as much as 20 or so % tps before it climbs to 30 - 31 degrees advance and goes on like it should. I'm not in tune with all this and sort of wish I had left it alone and I'm glad it's not my daily.

I do have a few logs I can post as soon as I can figure the posting part out, any help will be greatly appreciated.

p.s. the tune is a mail order from an interweb tuner.

thanks Mike

[steveo]

cant do much until we see the bin and logs

you could also try loading a stock bin to see if it runs normally and if it does demand a refund from your tuner

one thing to watch is your injector pulse width during decel. if its zero then you’re in decel fuel cutoff. thats important to know

[tumleweed]

I have seen the injector pulse width go red and all zeros on a few logs but not all and the advance go red too, here is the bin file and the logs I'm still trying to get a few on here.

I don't have the stock bin but would the tune generator on the EEHack web site be ok to use?

Thanks Mike

[steveo]

here's damn near every stock bin http://fbodytech.com/bin-files-2/bin-files/

the tune generator probably isn't a good idea for your caprice, it's for fbodies

there's no knowing which calibration he based yours on as he changed the cal ID to some nonsense, but i did a quick comparison and he did change a LOT of stuff. i compared against 16243941

way more than a normal tune-by-mail guy usually would usually change.

he did jack around a lot with your DFCO (decel fuel cutoff) settings a lot. still need a log to confirm but just guessing from what you're saying that the problem lies there somewhere.

if you have trouble uploading logs just right click and go 'add to zip file'.

maybe one day the admins will allow .eedata files..

[tumleweed]

would it (the engine) being out of a 9c1 caprice make a diff?

I will try one of the b body tunes , auto, 3.42 gears I have 3.55's in my truck?? here are 2 logs.

thank you and Merry Christmas!!

Mike

[steveo]

there's definitely something crazy going on there.

there's nothing in your spark tables to warrant that small spark advance so it MUST be using the DFCO spark retard even though your injectors aren't cut off yet.

try this bin (dfco changed back to more ordinary values) and please log

hope that fixes it and merry xmas to ya

[tumleweed]

I will thank you again

[tumleweed]

Steveo…. I loaded the bin file and it might be me but it seems to be a little more responsive just blippin the gas in park... I'll drive it to work in the morning and log.


Mike

[steveo]

nah, it's exactly the same except for the DFCO which only works when you're decelerating heavily while rolling

[tumleweed]

The DFCO fix did the trick Steveo!

here are 2 logs from today, some numbers look a little diff but it does just fine as far as I can tell. When I get a handle on all this I may opt for better gas mileage than the best performance.

Thanks Mike

[steveo]

glad that did the trick. the parameters i put in that bin were mostly stock and will still save you a ton of fuel, id probably just leave them assuming the transition is smooth

[tumleweed]

are the idle steps the same as the IAC counts and shouldn't they be around 35 at idle?

Mike

[steveo]

35? where did you get that number?

LT1s run better with more through the IAC and less through the throttle plates. i usually like to see 50+ at hot idle if not more, but you definitely want to maintain an operating range there (never pegged open or closed)

[tumleweed]

Why the inteweb of course!!! Haaa
I should have added with the hot cam... still in the 50 range?

[steveo]

should be fine. is it idling okay?

[tumleweed]

yea in park smells a little rich but there are no cats, stumbles a little in gear coming to a stop but doesn't stall.

can I ask... did those 2 logs look ok after you changed the DFCO?

[steveo]

depends what you mean by ok

i didn't look too carefully,

the decel does look correct now

your idle fuel trims are a bit off, maybe your idle fueling could use a bit o' work, but who knows. a 'fuel smell' at idle usually isn't a rich condition

[tumleweed]

Good deal... Thanks