sr20det running extremely rich... why

SON240sx Automotive
1

ok, here’s the scoop. the car runs/revs fine, but is running so rich there is a constant plume of black smoke released. there seems like a slight miss (not from ignition, more likely from excessive fuel…so lets call this more of a stutter). S14 chassis with redtop SR20DET (APEXi BOV, stock sidemount, T-25, walbro 255, stock injectors, stock ecu, stock MAF).

i am gonna list what i have checked and the values if i recorded them.

items checkd/replaced:

MAF - good, replaced with known good unit off running car
TPS - good, readings checked out
Stock BOV - removed, plumbing capped off
Aftermarket BOV - checked, no leaks at idle
Plugs (NGK BKR5ES-11, not recommended personally, but they do the job) - black fluffiness, but not wet
Injectors - good, replaced with a set of 370cc out of running car (swapped complete fuel rail to ensure no ‘ripping’ of O-rings
Adjustable FPR - good
Fuel pump (walbro 255) - good, pump on seperate switch
Timing chain - on spot, checked with VC off (obviously)
CAS - stabbed correctly, checked with VC off
Rocker arms/shims - ok, none off
Turbo - spools fine
ECU (#62) - good, replaced with unit out of running car…no codes
IACV - good, not showing signs of being bad (ie. high rpm/engine shutting off after consistant RPM is released and allowed to return to ‘normal’. when supply hose is removed, engine shuts off.
Coil packs - good, very nice and strong spark at plug
Coolant temp sensor (ECU) - resistance checked at various temps = ok
Advanced/retarted ignition timing - engine obviously runs differently, but the ‘rich problem’ did not change.
O2 sensor - working, voltage being sent to ECU. not that it really matters
Exhaust - good, no leaks
CAT - not clogged

Readings/values of sensors (checked at ECU and sensor themselves):

MAF - 1.1 below 2K, 2.2 over 2K
TPS - 0.5 closed, 4.3 WOT
Vacuum - 16mmHG @ ~ 1000RPM what backs my theory stated below is when i removed the one of the vacuum lines off the throttle body and noticed very little change in running/idle. normally this would cause the engine to shut off. To further test leaks, the MAF was placed directly in front of the TB to eliminate the intercooler and plumbing and there was no change. also, plugged all vacuum sources off TB and revealed no change in runnablility.
FPR - 38 psi @ 1000 RPM, increases with increase of RPM. Upon adjustment, there was no change in the runability
Compression (checked with TOB closed…i know i know, engine warm) - 150 PSI after 5 cranks, first crank shot gauge above 100 psi) across the board
Timing - 15 BTDC

Suggestions:

  1. Please feel free to post this anywhere and get more ideas, maybe someone sees something i overlooked.

  2. There maybe a vacuum leak that i cannot find (ie. around IACV, TB or somewhere else).

  3. IMHO, i know you/your dad/robin(wiring guy) dont want to hear this, but i believe it is in the wiring. this is a fairly difficult swap when it comes to wiring. what pushes me more toward this is that every once in a while, the car will start and run/sound fine. no black smoke, no stuttering…but as soon as throttle is touched the problem returns. also, when i swapped with a ECU out of a perfectly running SR the problem was worse…even more stuttering and fuel dump.

2

my first thought is the tps, it may check out at idle and wot, but there may be inconsistency in the swing, dead spots and such that it confuses the ecu

but you are probably right, it very well could be a break or bad connection to one or more of the sensors

3

Your plugs are off by one heat range… not sure why that would make it run rich but its worth a shot. Also try to unplug the O2 and TPS. Does the car only run rich at idle or through the entire rev range?

4

what plugs do you suggest? thats a cheap thing to fix, they fowl really quickly anyway…

its rich through the whole range. as my dad puts it… when he starts the car it fumigates the lawn.
there is a TON of shit coming out the ass end

5

BKR6E-11 copper V available at CT

6

^