ill try to keep this short and simple...

when im cruising slowly like maybe around 15mph or so and i let off and coast while in neutral the revs drop all the way to 0 and turn off so then i have to pop the clutch everytime to start it back up or just turn it back on with ignition

but if im racing at the track or regular speeding and i let off, the rpm drop to 100 or so where the lights flicker but it catches and never turns off gets back to normal idle

all this started happening after i got my new shepard transfer case put in, so not sure what all could be involved with that area.. thought it was my battery so i got a new one.. did a alt test while alt was still in car and results were fine

the battery has been relocated to the trunk for over a year now and i just now am having problems

Mods
bs 272
1000cc injectors
tial VTA
ECUflashed
ported intake/tb

things ive done so far to troubleshoot
-checked all fuses on battery terminal and fuse boxes-- all good

-did boost leak test--fixed the few i had

-replaced the battery because apparently it was low voltage and would start up at times (after replacing it was good for 2 weeks then problem came back)

-did alt test at auto one (came out ok but low

-did alt test at batteries plus (results said alt was bad not getting enough volts)

-changed out the Alternator and serpentine belt

-made sure the nut on alt power was tight same with other end

-made sure the harness plug going to alt was good and no broken/ bent pins in connector

-turned the car on with all accessories headlights/brake lights and disconnected the neg terminal (car stayed on after 10minutes waiting so alt has to be good right?)

-grounds look good from first glance (no aftermarket ground kit here)

-reaplaced all grounds with 4gauge (daisy chained)

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UPDATE: finally figured it out.. it was all in the VTA tune.. appearently i had a leak in my tial bov line when i was tuned for VTA a while back and when i recently found and fixed the boost leak it through everything off within the idle and afr. so just got my tuner to adjust and test a few things and now im good.. i hope

 

Take it to an actual shop that has a Vat 40 to test your charging system. Large vac leak? how are your spark plugs? And mods? tune? Please dont pop your clutch to start the car........

Edit: saw ur modded

Have you tried taking the battery off and letting it sit for a while then reconnecting to see if there is a change?

 

havent checked spark plugs. fp red stock motor and yes on same tune for 1 month and it just started doing it

why cant i pop my clutch

 

Popping the clutch puts a lot of stress on the drivetrain with such a sudden jolt, almost the same thing as launching your car.

Have you checked out your IAC motor yet? That could possibly be the problem too.

 

My car has ALWAYS had this problem...We adjusted the idle up to keep it from stalling and also adjusted the air idle control valve which made it better(no stalling) but idle still drops down and catches itself then goes back to set idle speed......it is really annoying, but at this point ive learned to live with it...

Things ive tried... plugs, wires,coils,Air idle control valve(adjusted and tried a different one),cleaned PCV valve, checked vaccuum hoses, adjusted idle in tune, battery,

also it seems worse if drop is from above 3000rpm..........

 

whats your idle set at? do you have cams? my car would act funny sometimes with my idle set at 850, set it at 1k and its been awesome since.

 

mines set around 850...running hks 272's.....but had the same issue even before...

 

I have the same cams, try to set your idle at 1k and see if helps.

 

The valve in the throttle body and the actual electrical part of the IAC are 2 seperate parts, if you were referring to the throttle body one. I had the IAC motor go bad on my car and sometimes it would stay running, others as soon as I pushed the clutch in it would die on me.

 

mine did it from the stock and greddy type s bov.
now on synapse it doesn't happen.

 

What voltage are you getting across the battery terminals when the car is running? If it's greater than 13.8 V, then the alternator is fine.

 

I had this problem on my car. Mostly when it's hot out and I had the A/C on, but when I had the tuned cleaned up I had my tuner change the stepping of the a/c idle or whatever it's called and the base idle rpm. mine idles at 1500rpm on cold starts and 1k when warm. I also havve 272 cames, but they're cosworth.

 

Do you have a wideband?...What's your a/f ratio at idle and what does it look like when you coming to a stop? Do you have a VTA bov that you aren't tuned for? May need to bump your idle up...

 

just did the following today

reset the battery removing the positive (still stalls)

took maf out to see if it was covered in dirt (clean!)

another boost leak test (found one on uppipe where the meth nozzle is)

also noticed a gas smell coming from intake mani side when doing boost leak test

-checked all my grounds to make sure they were tight but then just went ahead and upgraded to all 4gauge

driver fender to neg terminal to tranny to head to intake mani to chassis to passenger fender

 

my idle is at 1k

i have gears and bc 272 cams

im also running a tial bov (vta) tuned for it .. BUT recently found out i had a pinhole leak on the bov line so i replaced it and it changed the sound from a turkey to a regular slight woosh

kinda started happening after that