ISC yds active test stalls

[oldbay616]

when i run the isc active test, i see the ecu call for the numbers, i hear the air in the isc start to hiss louder, then motor bogs and stalls before the rpms increase... could this be a Bad ISC

went through the whole fuel system tank to injectors and are all fine. had a bad diaphragm in my low pressure fuel pump which wound up pouring fuel into the crankcase... after that i finally got it to idle relatively normal at least it will stay running now in idle...

another question if the oil switch is on as in sending a ground signal to the ecu, should the warning horn turn on immediately? or does it have to go through some sort of cycle or certain parameters before it sets the horn off... i hooked up a mechanical gauge to the oil switch port and was getting 60psi readings at idle.

i think when the fuel was in the crankcase it was dropping my oil pressure which putting the motor into limp mode but my hot horn was intermittent so it wasn't going off

[boscoe99]

Without knowing what brand and model of motor you have it is all but impossible for me to offer any advice.

[oldbay616]

2007 f90 txr

[greasyshaft]

Have you compression tested the engine?
When you throttle up does the engine stall?
What does the fuel pressure do just before the engine stalls?

Prime example of jinglish here....

[oldbay616]

compression 200's between all cylinders
leak down 5-7 percent between all cylinders
fuel pressure pretty constant at 42 psi, lowest was 39-40 when it was idling crappy..
took off the oil switch put a vacuum to it seemed to switch to continuity around 22 psi

here are some examples of my numbers when it was idling bad
Data Logger[Data comparison graph],
,Engine speed[r/min],Battery voltage (12-16)[V],TPS voltage
(0.5-4.5)[V],Water temperature (below 90)[°C],Intake pressure[kPa],Oil
press switch[0:OFF 1:ON]
,2100,14.58,1.80,64.2,89.3,0,
,2200,13.77,2.09,64.2,95.3,0,
,800,13.62,1.00,32.9,41.0,0,
,700,13.62,0.98,39.5,41.0,0,
,650,13.48,0.98,51.9,41.5,1,
,700,13.55,0.98,46.5,44.9,1,
,1500,14.06,1.15,62.5,45.4,0,
,550,12.67,0.98,48.7,47.4,1,
,800,13.40,0.98,44.0,42.0,1,
,1100,14.14,1.00,60.8,30.6,0,
,650,13.70,0.98,61.7,35.0,1,
,800,14.14,1.00,59.3,33.6,1,
,550,13.11,0.98,54.4,43.9,1,

one of the last times i ran it the last column was all 1's... this is what led me to believe the diaphragm of the low pressure pump was slowly leaking thinning down the oil, decreasing the pressure intermittently setting off that switch, the last time i ran it the primer bulb never got hard and i kept pumping... when i went to check the oil after the horn finally came on after i messed with it the dipstick about shot out as i pulled it and obviously thin fuel oil mix erupted out of that hole... since i replaced the oil and the diapraghm it starts and idles fine... so thats why i think it was cutting my rpms i was trying to diagnose a bad idle when all the while my alarm just wasn't coming on

however idk if i damaged the isc during that time... it gets pretty hot my temp gun says 150 but its painful to keep my fingers on it, the plastic pintle actually looks like it got some heat and wrinkled up the smooth finish.. so this is why i wonder if its intermittently bad.

when i hit the neutral button and try to rev it up it has a slight hesitation initially and then revs smooth and no issues when i drop it back down.

couldn't find any vacuum leaks. atmosphere is 30"hg runs at 8-9"hg so 21 22"hg of vacuum don't seem so bad, wouldn't expect that much vacuum with a significant enough

[pstephens46]

How would the low pressure fuel pump dump fuel into the crankcase?

[oldbay616]

bolts directly up to the crankcase, in the manual says to put 7 psi to the inlet side block off outlet and make sure it holds pressure...when i took the old one out it didn't hold pressure, sprayed it with soapy water and was bubbling around the tappet that pumps on the camshaft, diaphragm was torn and had come off the shaft. replaced the diaphragm and now no leaky...

[oldbay616]

so i replaced the oil and filter, and new isc.... it ran great for another 10 or so hours and now it will not start again... if i push in the neutral button and crack the throttle blades it will run and rev smoothly. but die as soon as i bring it back to neutral. any thoughts? when i got back to the dock the ISC was pretty hot to touch. no warning buzzer...

the ISC wiring has been replaced and good continuity to the ecu

could this be an ecu issue?
can the ecu be bad not letting the motor idle?