trying to diagnose stalls at idle with MSnS-E

[thechuckster]

hi folks,

important ECU/configuration info: is a MegaSquirt (MS-I) running MSnS-Extra, v.024s code, toyota VR sensor in a locked dizzi with 4-tooth wheel, bosch generic electronic ignition transformer coil, relay board, 4agze injectors (365cc/min) with resistor pack from a FWD toyota, narrow-band O2, malpassi rising rate FPR, ex-RB20 nissan turbo, external bosch fuel pump using carbi tank pickup.

am still trying to get my 18RTE to idle with some stability - but am having a ongoing battle with it stumbling and nearly stalling every 7-8 secs (unless i pump the thottle).

My logs show the O2 reading high (deliberately tuned rich), then it start to taper towards stoich, then suddenly plummet to extremely lean - this would indicate that the engine is running out of fuel.

But... if i pump the throttle - this suddenly increases the pulse-width - the engine stays running but with a bit of coughing and popping at much lower rpm... the AFR doesn't rise instantly - it seems to take a few goes at enriching things before the engine catches and we're back to a fast idle (~1200rpm with 6-8% throttle open)

... idle then stablises and we repeat this all again in about 8secs.

If i dont touch the throttle, the engine will stall about a second after the O2 bottoms out.

My query is: would a dodgy fuel pump have this kind behavior, or the FPR? or am i trying not to blame something in my settings?

petrol: i don't have a surge tank - but have just put 20 litres of new ULP into an empty tank - it was doing the same when tank had about 40+ litres of 2-year-old BP ultimate.

The gauge on my FPR does show static line pressure at what i think is 38psi with the pump on - once the engine is running, it moves about in tandem with MAP. Pressure does drop away when i turn the pump off (is this normal?).

I do have a an issue with the alternator not charging, but voltages at the ECU are ~11.8 Volts when running so i dont think it's a problem - it's not affecting pulse widths and sparkage.

Cranking is slow (~300-350rpm) but it catches easily.

when i pull the plugs, they're dry but coated in carbon (from running rich).

It's quite hard for me to get the car started and me out to the engine bay to watch the fuel pressure... it invariably dies before i can get to the throttle body and give it a bump...

It did have a stable idle previously - but am not sure whether changes in timing and fuel maps have killed that stability... was too many ECU changes ago ... ;(

Prior to this i've:
-dumped contents of tank (to remove risk of it being old, crap petrol)
-put new loom from ECU to engine bay
-checked all sensor wiring eleventy-trillion times - i can safely say these are all good now!
-replaced wires to TPS and O2 with shielded cable
-changed dwell from 4ms to 3 ms (was thinking that the spark might be not healthy enough)
-pulled timing back (at this fast idle, it was at ~30 degrees, is now about 24 degrees)
-tried timing locked to 12 degrees
-replaced the relay board

I had a weird wiring issue previously with the O2 input acting inverse to TPS behaviour - this is now fixed with a new loom.

suggestions most welcome...and sorry for the long post too

cheers and tia,
Charles.