240sx running rich as hell!

[AbsolutLoss]

ka24de dohc, running so rich the plugs fowl up immediately, light smoke at idle in exhuast (gets thicker if you stop fora second and then hit the gas) i think thats the valve seals maybe and im gonna do them tomorrow anyway cuz its fairly easy. when i unplug my maf sesor the motor revsup to 1200-1500 and its almost like cylinder 4 Has 50% power compared to others.stuck valve? not sure
before everyone states the obvious let me tell you what ive done
Good wet and dry compression 180 accross
Plugs
Plug Wires
Dizzy Cap and Rotor
Temp Sensor
Knock Sensor
Headgasket
head bolts
intake gaskets
all injector o rings replaced
all injecotrs dont leak and atomize correctly


issue? car sounds like a subie!!! cylinder 4 acts dead but kinda feels very weak wheni plug the injector back in there's a tiny difference but not noticable

[NukeKS14]

Did you check the ECU for codes?

Have you checked for vacuum leaks?

Might be MAF.

download a copy of the FSM from this site, go to the EC section, and start working through the troubleshooting procedure(s) if you get a code from the ECU.

[AbsolutLoss]

no vacuum leaks, completely forgot the first thing to check on these cars thank you! the maf is being a little weird the car doesn't die when i pull it, gonna replace it. i get an ecu code 55 which means the ecu does not see anything wrong with the car, but i know a good maf when unplugged should kill the ka24de. after valve seals are done and the new maf gets in ill update this post

[PapaSmurf2k3]

Yikes, that's rough.
FYI - Vacuum leaks will cause it to run lean, not rich. You might want to try pulling a vacuum line just to keep the thing running while you try to troubleshoot.
Its fouling all the plugs right, not just 1?
I think there's only a few things that would allow the car to run that rich. MAF and coolant temp sensor come to mind first.

[NukeKS14]

I don't know what's been done but if your base fuel pressure was too high... could cause this too. Check the manifold reference to the FPR. Should drop fuel pressure down at idle based on vac reference. My initial thoughts were bad clt sensor (seeing low coolant temperature would lock in warmup enrichment) but you said you replaced it and its not throwing a code for that so, fuel pressure or maf are more likely culprits.

[PapaSmurf2k3]

IIRC I also didn't have a CEL when my coolant temp sensor went bad... but that might be because I never let it run long enough (or it wouldn't run long enough) to actually enter any closed loop control.

[NukeKS14]

Yeah that's the downside to the stock ecu; it generally won't throw a code unless sensor voltage is 0 or 5v. Sensors can fail at a value the ecu considers in range that is still incorrect for actual engine parameters. Still, itll tell you if the wiring between the sensor and ecu is jacked. Better than nothing.

[ROULETTE77]

dealt with this recently
maf is very sensitive ,
carefully clean it make sure the plugs terminals are clean and making good consistent contacts inside the terminals. MAF likes smoothed air flow, least amount of swirling or back and forth air the better, so if its other than oem air filter or box think of it in those terms.. this made the biggest difference for me . .my sr is in a tiny engine bay , no room for oem air box... my MAF had such confused signal due to turbulent air, that it ran exactly like yours sounds...

also check your TPS ... set to correct voltage? remove and clean throttle body front and backside of throttle plate , inspect this area for smooth mating of walls to plate...should have a tiny air gap not fully closed to the wall when throttle is full off. . .clean intake when TB is off.. also o2 sensor could use a checking

[4felix20]

I stumbled in here off of curiosity and I haven't had my s14 for a long time, but I vaguely remember having a similar problem and my o2 sensor went bad. Not sure if they're related and my experience is limited, but it's easy enough to check and used to be a cheap part. Good luck, I hope it's something as simple as that plug.

[AbsolutLoss]

Update:

The car will idle now when it is warmed up. I need to hold the gas to keep it alive
I’ve gone over all the wiring harness for the injectors and sensors. New plugs again. New o2 sensor. Cleaned very well iac valve and new gasket. Found a vacume leak and fixed that. On the 4 kinds connecting to one under the intake.
New maf sensor. Valve seals are done.
Plugs look great now no more rich. But the damn car still sounds the exact same. And can’t hold it’s own idle. If it does hold an idle. It’s around 850-1100 rpm and if it goes lower it stumbles.
I have a summit racing 255lph external fuel pump pushing 43.5 psi on the stock fuel hoses. With a summer racing fuel cell in the trunk. I have purchase a new fpr and I’m going to purchase all new 370cc deathswerks injectors in hopes that maybe I have a sticky injector. Timing is dead on. Ignition side is all new. Everything except the injectors and fpr.

Besides those. Is there anything else I can look for. I really think this is it. And if the new injectors and fpr and maybe fuel pump don’t do it. I’m gonna assume the head or block is bad

[AbsolutLoss]

Question. 370cc or 270cc I know stock is 270cc but if I get the larger ones for future turbo build. So I don’t have to purchase another set. Could that be done? Or no. They are the same price 369$ for the 370cc or 270cc

[4felix20]

Timing? I f*** up my distributor install once...

[PapaSmurf2k3]

Can you open the IACV screw to see if it improves? Should drop the dutycycle to the solenoid. Also, it doesn't sound like a spark problem, and you said timing is dead on so you should see if leaning it out or richening it up makes any improvement. If its just 1 cylinder misfiring (which you can tell by unplugging a plug or injector from and not seeing a change), address that cylinder. If its random, give it more fuel by any means necessary (pull a vac line and put some fuel down it) or lean it out (pull a vac line and don't put fuel down it) to see if it improves. Ultimately a wideband O2 would be best, but if nothing else, if its running stupid rich you should be able to smell it.

[ROULETTE77]

get that pump in the tank...under "water" it has a cooling and calming effect ...there designed to push fuel and do fluctuate when sucking through a straw.. get that pump set up so its intake has a proper high flow mesh bag filter
new maf is good, did you address any flow issues to and from the maf ? when air is turbulent in that tube it can swerl pass the maf more or less than the expected volume...the ecu over then under compisates..this is why the idle bobs up and down...when it under comp.s a few times in a row that's...falling in its face...worked on this for 3 years to solve my packaging issues on my jdm s14 1969 datsun roadster . my maf is 5 inches from my turbo's intake runs consistently...14.7afr....idles like a kitten screams like a banchie Bov vent to air with no issues...paaachooooo krackell...brrrraaaaahhhhh
try air straighteners...worked wonders for me before and after the maf

[ROULETTE77]

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