Hey guys I've run into sort of a weird issue and I am stuck at what it could be.

I had noticed that my car would go ridiculously rich(<10 afrs) sometimes and if I let off and go back on the gas it would disappear but lately it does it no matter what I do except if I were to go WOT it goes and sits at about 11.5-12 afr which it should do. so far I've done the following trouble shooting:

1.change out stock FPR for a aeromotive one, set the pressure to 40psi without vacuum and when vacuum is plugged in sits at 34psi. No difference at all
2. redid all grounds and added 3 additional ones. Much better lighting but still no difference
3. replace Coolant temperature sensor(not the gauge one but the ecu one). No difference
4. Checked for boost leaks. When I did this I found I had a boost leak right at the throttle body which I fixed but I also heard a very loud squeal from the back of the motor near where the head meets the block(bottom of intake manifold). At first i thought it was a the big o-ring that keeps the injector in and replaced it(it had a small rip anyways) but then I realized it wasn't that and I could actually feel air pressure from underneath the manifold.

I think the intake manifold gasket has to be replaced but I just wanted to get some other opinions before I did that(still have a stock manifold and it's a PITA to remove as you all know).

PS: the build is:

built ka24de(ross pistons, eagle rods)
stock head
650cc injectors/z32 maf/tuned ecu(chipped)
t3/t4 50trim turbo

Thank in advance .

What year car? What's the tune? Changed O2 sensor(s)?

biggie wrote:What year car? What's the tune? Changed O2 sensor(s)?

it's a 1995 240sx, the tune is a custom tune done by a local tuner for 650cc and z32 maf. not running a O2 sensor at all.

There is definately an issue then. Never seen a MAF system without an O2, ECU is probably reading lean without an O2 and dumping fuel.

Correct me if am wrong but don't our cars have a open and closed loop one for if the o2 is hooked up or not?

Don't think so, but I do suck at eletric stuff. As I said, never seen anyone with ECU/MAF setup without O2, the ECU is always looking for O2 input to adjust fuel. No chip I know of would change that.

any tuner should be able to disable o2 feedback via the map and the flag. I have my plx running to the oem o2 wire but its just so its not hanging.


suck through?
bov recirc? if not it may be venting some at cruise.
boost leak?