S14 RB20DET,WHOLE YEAR STILL ISSUES...LIL ADVICE PLEASE..:D

[craz4240]

Well long road.Posted on this subject a couple times talked to Carl about it a few times but now it's down to the wire and looking for ideas that may support or possibly object my own.

Car is a 95 240sxPowerplant is RB20DET

equipped with Z32 MAFS,GTR FMIC,2.5" Cooler piping,t-bolt clamps,RX-7 Series 5 Injectors,Custom Built RB25 Turbo,Toyota Supra Lower Injector Isolators,Carl H tune.

K well the car idles at 22.4:1 AFR's and seems to be a little over the map under load.I have had the injectors flow tested and cleaned,all new gaskets for the IAC,TB,Intake upper and lower plenum,supra lower isolators,New hoses for all vacum lines,injectors tested for power and pulse,spark operating fine,CAS operating as it should.Car fires first try but the lean idle alarms me,also it's not really drivable,seems to work better when cold as opposed to once it gets hott.

For the record I had all the same problems b4 I did the gaskets,flowed and cleaned injectors,added GNX coil upgrade.

I still have someone bringing me a spare Z32 MAFS to try out tomorrow,and i plan on just plugging in a stock tune adjusted for MAFS and Injectors Only see how it idles.

Sorry for the long winded explanation but theres alot going on here hehe.Any advice or suggestions would be appreciated.

[240z4u]

Smart move going back to a more "stock" setup.

First thing, check to make sure you maf is wired right. Also, is your o2 sensor working? You are in closed loop and it does use o2 feedback. Is your heater actually working on the sensor? Outer two wires will show 12v. My a/f at idle would float ALOT at idle when my sensor had no heater connected.

Evan

[craz4240]

Carl had turned the o2 feedback off so the ecu is no longer using this.I have thought about the MAFS wiring as well,I have taken the wires up and around the back of the motor to avoid interference from the Alternator etc.I know as a rule the car should run worse with the MAFS un-plugged the car runs a little rougher at idle with it unplugged but the AFRS go to 10:1 at idle.Also the car doesn't fully die when I unplug while it is running it cuts out then catches again.The tune Carl did is for 18psi,this turbo I have was built to be efficient at that boost (bored housing etc. etc.),but maybe a simpler more stockish tune may help rule out that as an issue.

[Carl H]

you should also mention that your 'idle' is 2k...

[craz4240]

With the idle switch set it isn't though,it is right around 1k I know still high atm it is high cause it has to be reset.

What do ya think man.....not blaming the tune just trying to rule things out by process of elimination and drive this hunk of **** for a change.

[Darius]

With that high of an AFR, are you sure you don't have any exhaust leaks downstream of the turbo and upstream from the wideband sensor? Air vacuuming into the exhaust via a leak at idle could throw it off.

[craz4240]

Normally I would cocurr with ya Darius however I just put brand new gaskets on the exhaust mani,turbo,and turbo elbow,also all new bolts and studs,cleaned all threads and used locktite on everything,checked 4 times everything was tight.

Running open DP atm just cause I never jacked the car up to refit the exhaust yet.

[DriftX]

where is your wideband at in your exhaust?

[craz4240]

It is on the elbow where the stock one goes..and i know this will kill the sensor.....however if you heard the car spit and sputter and act all wonky once the AFRS go super lean you'd know it' working.

Funny thing is the car runs half decent...14.5:1 when I first start it up cold (however I think Carl has theoretical set to 12:1),once it starts getting warm the AFRS go to ****.Then after I turn it off it is real hard to start up again,if I start it cold it starts no problem,if I start it cold..turn it off and start it again it starts fine but after it warms up and goes lean it is a pain to start back up...I'm guessing due to the high EGTS fouling the plugs.

This issue is real mind blowing and I know it's a long shot for it to be diagnosed over the net....but the ideas you guys have are very good and helpful,please keep them comming.

Also I have checked resistence on the coolant temp sensor tonight it is operating as it should,idle switch is set but yes it is still idling high for sure and even though it's open dump right now I can still tell by ear,spark and fuel is pulsing as should...:S

[jdmser]

I had the same problems when mine went back together and still do but not as bad. I have noticed there is some correlation between how I turn the wideband on and the leaning out at idle. I'm using the analog signal o2 signal from the lm1. If I start the car before I warm the o2 sensor it leans out. Now, if mine starts leaning at idle all I have to do is make a few wot pulls and it go back to idling at 13.5-14.5. I also think it has something to do with the alternator as well. When my fans kick on my afrs go up to 15.0-19.0 and she starts to stumble real bad. A Quest alternator and a new battery ground are in the near future.

Heres a list of everything I did to get to this point.

Had the intercooler piping rewelded and all leaks fixReplaced ECTReplaced IgnitorFlowed injectors and found out 660cc was really 730ccReplaced chip from Carl with new chip from Carl(Thanks Carl)Hard wired widebandRan 10 gauge wire from battery to fuel pump using relay

[craz4240]

I had the same problems when mine went back together and still do but not as bad. I have noticed there is some correlation between how I turn the wideband on and the leaning out at idle. I'm using the analog signal o2 signal from the lm1. If I start the car before I warm the o2 sensor it leans out. Now, if mine starts leaning at idle all I have to do is make a few wot pulls and it go back to idling at 13.5-14.5. I also think it has something to do with the alternator as well. When my fans kick on my afrs go up to 15.0-19.0 and she starts to stumble real bad. A Quest alternator and a new battery ground are in the near future.

Heres a list of everything I did to get to this point.

Had the intercooler piping rewelded and all leaks fixReplaced ECTReplaced IgnitorFlowed injectors and found out 660cc was really 730ccReplaced chip from Carl with new chip from Carl(Thanks Carl)Hard wired widebandRan 10 gauge wire from battery to fuel pump using relay

I have the quest alternator here but i am not hooking it up till I am sure I need it,I should check my fuel pump and make sure it is getting 12v or greater.This car is gonna be the death of me hahaha

[craz4240]

I'm out of ideas guys HELP lol.

[craz4240]

K well heres the latest.

Took off the AAC/Cold Start Valve....took it apart to check the spring etc.It was ok.....nothing disconnected,clean nothing wrong,sealed that back up with a light bead of nissan rtv.

Made a new observement however, the afr's are great on startup car has a spitting noise not sure what that is somewhat seems like a misfire I guess...I attribute it to the lean afrs and when i give it load it smoothes out,runs good at first at stoich ie:14.7:1,once the temps get to about 80 celcius dunno what that is in farenheit but the afr's take a dump on me....today the car got up to 83 (turned off fans aren't hooked up yet) afrs were 20.2:1 up and down to 19.x:1.

The afrs creep up gradually the longer it runs.Seems to run reasonable afr's under load today anywayz lowest was 10:1 which is alot richer then the ecu is set for.I am freaking lost I have more stuff to try but hoping for a third party insight.

[craz4240]

Did a test on vacum tonight with a jug of brake cleaner,no idle changes anywheres at all...stil doesn't totally rule out vac leak however it's what i had to do till I could get use of the compressor.

Also checked voltage on the MAFS pin B (Z32 MAFS) and ground it was .656 with key just on and it was 1.97 at 80 celcius....seems reasonable to me manual says .8 and 1.5.....what do you guys think?