Engine Won't Run With Afms - Please Help

[RB240Dav]

IT RUNS, OMG, DOES IT EVER RUN!!, WILL HAVE IT ON THE ROAD IN A FEW DAYS!!!

Hello again gents.

I have a mystery of a problem here. Bit of a long explanation but here it goes:

I have a 1990 S13 240sx with an R32 RB26DETT in and running.

I have the turbos, intercooler, and piping temporarily run with PVC. It's sufficient for plumbing design, fitment, and testing. I have built a downpipe to keep the stock twin turbos which is connected to a full 3" exhaust.

I do have several vacuum/pressure lines unhooked, however they are plugged (not well mind you). I have not hooked up a boost regulator or the BOV's yet. Better to get the motor running well first before worrying about getting that worked out.

When the AFMS are unplugged the motor starts at the turn of a key and runs rather well in "limp mode." It's rpms settle in around 2200 most of the time, sometimes around 1600. The motor responds to the throttle by idling down further. It is ofcourse running overly rich to the point it stings your eyes a bit (I figure this is normal as the engine will dileberatly run overly rich to prevent internal or turbo damage). At no point can I get the motor to go over 3000rpms, once again this seems normal for not having AFMS plugged in.

O.K. now the interesting bit:

With the AFMS (stock r33 ones thanks to HUNGRY 6) plugged in the motor will start, but only up to approx. 800rpms before immediately shutting down. The same goes for having in combination either AFM plugged in one at a time. As well as, with the engine running, if I plug in one AFM the motor will sputter for 1/2 a second and then shut down.

I am beginning testing of the wiring harness and other sensors however this process is tedious and even the solution can be overlooked. I have tested the fuel pressure and it hits pretty close:

Test ....................Standard........Actual

Ign. On ..................43psi .......... 40psi

Idle .........................36psi .......... 39psi

Idle w/o vac line.......43psi .......... 45psi

Here are my thoughts:

In "limp mode" (am I calling it right?) the ecu gives me a set amount of fuel and timing, without knowing how much air is coming in, it's ignoring most of it's other sensors.

When the AFMS are plugged in the ecu then attemps to set the correct air-fuel mixture and appropriate timing. Some other sensor (now that it's out of limp mode and being monitored) could be giving faulty information causing the motor not to run.

Or, something else is seriously wrong and ignored in "limp mode," hence when the AFMS are plugged in the ecu responds by killing the motor. i.e. Faulty ECU or Knock sensor.

Also, it's probably not something tuning related, i.e. bad O2 senors, boost/vacuum leak, etc... I believe these sort of issues would cause it to run poorly, not necessarily shut down the motor.

-------------------------------------------------

There are a world of things to test for, however I'm hoping that someone with a little more experience with the RB series than I (which would be none) could help point me in the right direction as I am pretty well stumped here.

Any thoughts no matter how small or seemingly trivial will be helpful. Our collective brain storming might get me going down the right road.

THANK YOU, THANK YOU in advance, This is a full 1 year prodject nearing it's completion and I am beside myself trying to get it finished.

P.S. located in the middle of the U.S.A. there are virtually no tuners within 5hrs of here that have ever seen an RB motor.

Edited November 2, 2005 by RB240Dav

[RB240Dav]

Some random pics so that ya know I'm for real B)

[CEF11E]

With running the RB25 AFMs, What sort of ECU are you running?

if you are running the standard ECU without any extra calibration (SAFC or other) you will not get it to run.

However I would be guessing you are running a PFC?, if so have you selected the correct AFM's on the PFC?

hope this helps...

[RB240Dav]

I'm using stock r33 rb26 afms on an r32 rb26, I have been told that they are the same. And I am using the standard computer.

[Sydneykid]

The reality here is you most likely have a whole host of sensor/wiring problems. Limp home means nothing more than 2,500 rpm. In fact "limp home" is a bit of an overstatement, more like "limp to the side" of the road".

The best diagnostic tool I have is the Consult interface, I guess that comes from years of reliance on the Power FC Commander. They let you see, in real time, the inputs from the sensors which makes fault finding so much easier.

There are a number of them available on the forum;

I just ordered one of these, I like making up kits

http://www.skylinesaustralia.com/forums/in...showtopic=92853

If you don't want to make up a kit, I have used one of these a number of times and they work great;

http://www.skylinesaustralia.com/forums/in...2617&hl=consult

I haven't used on of these, but plenty of guys have;

http://www.skylinesaustralia.com/forums/in...showtopic=92105

Without one of these you are going to spend hours with a multimetre chasing around the wiring looking for an answer. A Consult interface will help you find it in minutes.

Hope that was of some help

cheers

[RB240Dav]

Well, this is about to become one hell of a learning experience since there is no easy way out.

It's time to get down and dirty, and I'll let you chaps know what I find.

I'm sure you hear it a lot SK and I hope you never get tired of it. . .

THANKS.

[RB240Dav]

I want to run a code check on my ecu by counting the l.e.d. flashes on the ecu, but I have a Nissan Remanufactured One, and for some reason it doesn't have any lights or dials on the back of it, WTF!!

So anyways, I know that you can also count the "check engine light" flashes. I'll splice into the wire coming from the ecu to the light but I don't see a "check engine light" on the instrument cluster I've got (it's not installed) What light flashes?

[Sydneykid]

  RB240Dav said:

I want to run a code check on my ecu by counting the l.e.d. flashes on the ecu, but I have a Nissan Remanufactured One, and for some reason it doesn't have any lights or dials on the back of it, WTF!!

So anyways, I know that you can also count the "check engine light" flashes.  I'll splice into the wire coming from the ecu to the light but I don't see a "check engine light" on the instrument cluster I've got (it's not installed)  What light flashes?

<{POST_SNAPBACK}>

Yep, most of the ecu's don't have lights, I kinda figured you wouldn't have a GTR dash in there for the "Check Engine" light to flash codes for you. That's one of the prices you pay for an engine swap. Hence why I suggested the Consult interfaces.

Pin #32 is the output from the ECU to the dash warning light, so try wiring a 12 volt 1 watt globe there, if you can't wait for a Consult to arrive.

cheers

[RB240Dav]

I remember reading about two wires you short (if you have the diagnostic connector you can jump the pins) in order to get the ecu to flash the codes to the dash. I can't seem to find the thread now, anybody know if I'm on the right track again?

SILLY SILLY QUESTIONS.

Thanks again SK

[RB240Dav]

IT RUNS, IT RUNS, IT RUNS!!!!!!!!!!!!!!!!!

There was a break INSIDE the wiring harness (damn importers don't know how to properly pull a loom)

I was wiring up the check engine light to run the codes. So I had to move the harness around a lot, plugged in the mafs. Gave it a turn for the hell of it, and it started, and ran.

OMG, IT SOUNDS SO GOOOOD!!!

THANK YOU ALL!!!!

[Get-Reddy]

Good to see you got it up and running, have fun with it.

In those pics youve got quite a car yard there, is that a FC RX7 in the background?

[GunMetalR33]

Good to hear mate, I must say I figured you were in for a ruff ride getting the thing to start. Dam electrical issues are the worst!

[RB240Dav]

  Get-Reddy said:

Good to see you got it up and running, have fun with it.

In those pics youve got quite a car yard there, is that a FC RX7 in the background?

<{POST_SNAPBACK}>

Thanks,

yeah it's an FC. Rather unfortunate incident for the owner, poor guy. . .

It was near mint and he stored it in the winters. (he's 23yrs old) So he pulled it out of storage this spring, started it up and ran out of gas about a mile down the road. Was gone for 15 minutes to get more gas and when he came back the fire department was there putting his car out. The battery cracked and leaked acid onto the harness underneath all winter long, and then wham, catches on fire. Thankfully it went up on the road and not in storage where there were 2 other rare cars. He's going to work on wiring it back up this winter, as you can see, he already replaced the panels.

The motor just screams, I should have it rolling in a few days, just have to finish the intake, brakes, alignment, and install driveshaft. All the tracks are closed, so I'll have to find someone with one of those G-Force tec thingies to get a 1/4 mile estimate.