OBDI running rich and 1221 code

[ParsedOut]

My OBDI M50 vanos swap has been running rich and throwing a 1221 code since I put it in. I know this is a generic code that tells me the car is running rich or lean, other than that it's useless in troubleshooting. If I reset the ECU (disconnect battery), the light will stay off for approx 10-30 miles. When it comes on (and stays on) it's during light acceleration, usually shortly after taking off from a stop. I know it's running rich because I'm only getting 20mpg with 50/50 mixed driving and 3.64 rear end, not pig rich but enough to be obvious.

Motor is bone stock with a 413 ECU. Fan clutch deleted with Mishimoto radiator, I also believe the thermostat has been removed (need to take care of this) as it takes forever to even tick above the cold/blue. The ECU isn't mounted in the glove box yet, it's just hanging there for the time being, noticed it gets fucking hot as hell. Not sure if having it mounted (heatsink) would help or cause problems if not?

When the ECU is freshly reset, the car pulls like a beast...well as much as you would expect from a stock M50. Once the check engine light comes on, it feels like it's down 30 hp and the idle becomes a little less silky. Overall the idle is solid at 600-700 rpm regardless. I've also noticed in the morning when the car has been sitting all night, that there is a VERY slight hesitation at light throttle cruising speeds, most people probably wouldn't notice it but I'm on high alert lately. A few miles down the road it goes away.

Here are a list of things I've done to trouble shoot so far to no avail.

VANOS was rebuilt shortly before swap, makes no noise and can feel it work as it should)
Tested for vacuum leaks (carb cleaner method, was very thorough, surprised no engine fire! lol)
Replaced O2 with genuine Bosch
Replaced MAF
Replaced injectors and FPR
Replaced old ICV hose
Cleaned ICV (moves smoothly)
Replaced spark plugs
Replaced main/fuel pump relays
Replaced both fuel pumps (for unrelated reason, but they are fresh)
Replaced fuel filter
Tested fuel pressure
Replaced leaking valve cover gasket
Replaced CCV and CCV hoses
Replaced oil filler cap
Bypassed EVAP system (for troubleshooting purposes)
No audible exhaust leaks
Not losing any coolant
Drinks small amount of oil (no blue smoke)

Haven't replaced the CTS yet, but would expect much greater drive-ability issues if it were bad. Same with CPS.

Is it possible my lack of thermostat is causing the ECU to get confused (running too cold)?

Hmm...just had a thought, the EVAP valve is ECU controlled. Does anyone know if the ECU is set to bump the fuel delivery to offset the expected additional air injected into the system when activated? Seems like an off the wall thought, but I'm running out of ideas here.

Any ideas or insight would be greatly appreciated.

[justin_l_]

If your car isn't running at proper temp it won't run correct, fix your obvious issues first the. Get back to us.

[NickL]

Without a thermostat and the CPS reading the coolant temp cold all the time the ECU will run the car like its cold. With the 02 and MAF telling it different things then the CPS its most likely quite confused as it needs the CPS, Maf, and o2 to know when to run the car in closed loop.

[ParsedOut]

If your car isn't running at proper temp it won't run correct, fix your obvious issues first the. Get back to us.

Without a thermostat and the CPS reading the coolant temp cold all the time the ECU will run the car like its cold. With the 02 and MAF telling it different things then the CPS its most likely quite confused as it needs the CPS, Maf, and o2 to know when to run the car in closed loop.

Thanks guys. I didn't concern myself with the thermostat all that much because at first thought, as long as the sensors are reading correctly then the engine management should know what kind of fuel enrichment to run based on the conditions. If it's running cold for longer than it should, then it needs more fuel during those conditions to keep it at stoich.

So as "obvious" of an issue as it is, I'm not dead certain it'll fix the problem. However like I said initially it is something that is getting taken care of.

I'll report back, in the meantime any other suggestions?

[techno550]

If the thermostat has been removed, then the port in the head needs to be plugged. If not, it will overheat. So it either has a thermostat (possibly a bad one as they fail open), or its been modified to not have a thermostat.

If the engine is too cold, it will not enter closed loop.

The O2 sensor only knows lambda > 1 or lambda < 1. It does not know how far. It only looks for the crossover.

[ParsedOut]

If the thermostat has been removed, then the port in the head needs to be plugged. If not, it will overheat. So it either has a thermostat (possibly a bad one as they fail open), or its been modified to not have a thermostat.

If the engine is too cold, it will not enter closed loop.

The O2 sensor only knows lambda > 1 or lambda < 1. It does not know how far. It only looks for the crossover.

Interesting, not exactly sure what the PO did to the cooling system. It also makes sense that the code doesn't kick on unless I've been driving it for a while, seems like as soon as it switches over to closed loop mode it fires off the 1221 code. That line of reasoning gives me even more reason to not suspect the thermostat for cause of this problem. The code doesn't come on nor does the ECU read the O2 sensor output until the car is warmed up enough to be in closed loop mode. If I had severe drive-ability issues when the car was cold, then it would be an easy decision.