low engine speed mis goes away above 2000

[nathanhardy]

So ive been fighting this off and on for about two years now. the car otherwise runs strong, I cant pin point it but pulling wires or injectors so its got me wondering if its MS maybe dwell related. Ive also used a temp gun to seen if i could find it.

[slow_hemi6]

Log does not show any sub 2000 running.

[nathanhardy]

Log does not show any sub 2000 running.

yeah sorry about that went out to data log and realized i didnt have my bluetooth usb adapter. i left it in my friends car that im tuning. so i think it might be my over run fuel cut below 20 kpa is i think just a tad too high, the other thing i was think was may my spark duration might be too short!

[billr]

Why so low on the spark and dwell times?

[nathanhardy]

Ifound a write up on the msd gm twin tower coils and those were the times found using a scope.

[slow_hemi6]

I used to run the GM twin towers at 2.5 nominal, 0.5 duration and 3.0 cranking.

[nathanhardy]

I used to run the GM twin towers at 2.5 nominal, 0.5 duration and 3.0 cranking.

Isnt that how I have it set? What would happen is I added to the duration? Honestly I think the hesitation is coming from the fuel cut... but the car has always sounded like it has a miss even the engine builder I used said the same thing yet it runs strong and nothing seem out of place. Its only noticable at idle and just off idle... been banging my head on it for a long time..

[turbo conversion]

Have you done a compression test to check cylinder to cylinder balance?

David

[nathanhardy]

Have you done a compression test to check cylinder to cylinder balance?

David

Yes compression is 120 across the board at 8:5:1, leak down was great less then 10% @100psi... The motor is in great shape that why i can figure it, ive replaced wires plugs injectors tested all my wires, its batch fire ms2 it could possibly have bad lifters as i was stupid and didn't replace them after some valve contact but they were looked at and tested closely non the less when i switch cams here im gonna switch them obviously. what has always blown my mind is when i pull the plugs off the injectors it doesnt always drop out and stumble.

[turbo conversion]

Can you post a log of an idle with of the issue happening?

David

[nathanhardy]

Can you post a log of an idle with of the issue happening?

David

will do asap im going to go buy a new usb bluetooth adapter tonight...from what i can tell i data logs im not really seening anything that stands out

[nathanhardy]

okay got a low rpm data and two at idle..

[nathanhardy]

also changed my tune a bit. logs go idle idle 2 and three i tried to time them so we could see enrichments drop out

[turbo conversion]

Is 2 deg. timing correct at idle, if so why?

David

[nathanhardy]

the timing map is a direct copy of a gaic chip i think the vr6 motors like lower timing maybe im wrong tho, can that cause a constant mis sound out the exhuast or do think its just my 262 cams

[turbo conversion]

Is 262 the advertised duration for the cams?

If so at idle it will probably have a little bump to it but should clear up well before 2000 rpm.

Try experimenting with the timing at idle and see what happens.

David

[nathanhardy]

So I think it's just cams 262 is the advertised duration.. I finally got to do some steady state tuning using left foot braking and the car is so much more crisp and ego seems to react quicker and stabilizes... After all that it's still there but it doesn't hesitate I think what might have been happening is too much fuel and too much tip in fouling up my plugs after I would drive at steady state on the freeway and exit the next few idles were perfect! Then it comes back a little I'm still working on it down low too the car idles at 13.2 I feel that is rich but it seems to be where I get the best idle stability, it's hard to get my friend out that drives my car with his work. So tuning has been a long process