Hey guys, need some help here
I've had this problem ever since I was N/A, although it was a LOT less pronounced than it is today. Basically, when the engine warms up and the idle settles at its normal operating rpm (around 800ish, with 15 afr), letting the rpm drop from anywhere above ~1500 rpm causes the engine to drop past 800 rpm and die. When it drops like that I'm getting readings of ~10 afr (maybe lower, the UEGO sometimes takes a while to register really rich conditions, and only reads down to 10). Sometimes it will catch itself, bounce up and down for a couple seconds, then even out, but nowadays it usually just bogs out and leaves my wideband reading a solid 10.
The second symptom is rich throttle transition. When I feather the throttle (just baaaarely giving it gas) it causes it to run really rich, again sweeping the wideband to a 10. It seems to hesitate when I get on the throttle also. If I'm in a parking lot or something, and have a jerky start (350z pp and 6 puck rated for 500hp, what) if my foot accidentally bounces on the throttle it will jerk VIOLENTLY, causing my foot to hit the throttle more, which makes it worse. I have to clutch in at that point, while also holding the gas so it doesnt die, then slip the clutch a little to get going smoothly again.
This also happens in second, and to a lesser degree in the higher gears. If i get off light throttle, then get back on in quick succession, it'll jerk roughly. Pisses me off. It especially likes to happen when I'm cruising at low speeds, but just barely need to touch the gas to keep myself going. Goes really rich when it does this, and will afterfire if I get back on throttle.
Everything besides throttle transition and idle is fine. Feels a little sluggish at wot, but pulls good afrs.
TL;DR: Once warmed up, car dies when clutch is pushed in and rpms drop, wont catch itself at idle. Throttle transition sucks, jerks around a lot. In both of these situations it goes really rich, with afr @ 10. Fine afrs under constant accel.
EDIT: car is also hard to start when warm. cranks fine, but doesnt catch unless i fiddle with the ignition and give it gas.
Now, mods and diagnosis:
S14 KA
S13 harness, coil, distributor, etc
Most of the Greddy 20g kit
Z32 MAF
440cc injectors
Enthalpy tune
What I've done recently to solve it:
Boost leak tested at ~25 psi, didn't hear any obvious leaks
Pulled codes, found 34, 12, 13
Cleared codes, 34 and 13 still showing up
Wired in a resistor to emulate a knock sensor, as my KS wiring circuit is bad. Resistor brings signal from ECU down to 2.05v, no more code 34.
TPS adjusted from .44v closed to .5v closed, currently reads .5v closed 4.35v open
Pinched and disconnected fuel pressure regulator vacuum line, no change in idle?
Disconnected MAF and started car. Idled lower, ~500, but still dropped a little when I let the rpms fall.
What I think may be wrong:
Bad MAF wiring/grounds - I'm not sold on this one though. The fact that it still did it with the MAF unplugged makes me think it isn't related.
Bad coolant temperature sensor - A possibility, although I wouldn't think it would cause this serious of a problem. Still have code 13, popping in a new one tomorrow.
Bad fuel pressure regulator - This is my new target. It worries me that it doesn't change the idle when I pinch or disconnect the vacuum line. I'm thinking maybe the diaphragm inside is sticking? or caught? Could be holding it at a pressure level suited for being on-throttle even when it goes back down to idle, causing extra fuel to be injected and it to bog down.
I can get pictures and video of my setup if that'd be of assistance.
I've been dealing with this for like a year now though, and any help would be appreciated
so fed up with this car, missed a fucking awesome Dspot event with the Tuercks and Drift Faction guys today because I thought I could have it fixed once I pulled the codes, but nope...