RB not idling/revving correctly, HELP!

[gawdzilla]

Please give me some suggestions on making my motor run right! ok, so heres the deal.

start the motor, it always starts up right away. Get good oil press, etc. etc. idles fine, goes to about 950 rpm like the FSM says (rb26). When I rev it a bit, slowly, it can rev up and crawl to an rpm. When I start moving the throttle (letting off and getting on it), the motor starts getting weird on me. It pulls timing like the motor is knocking, and the rpms bounce up and down while the motor is compensating to catch itself. It seems like it is reacting too slow or something, between bogging and running too high for an idle. When that starts, I cant hold a steady rpm anymore, the motor sounds SUPER hesitant on the verge of death, and the motor eventually dies and cuts out.

Things I've done:i adjusted the idle via the screw w/ the AAC plug off, at about 950 rpm. I know the AAC is working cuz when I unplug it the motor ramps up. I took it off yesterday to clean it, checked the ssolenoid, and also read the voltage across it while the motor is running. Voltage crawls up slowly as the motor warms up, and while its going kinda crazy, the voltage is jumping around so the AAC is trying to catch my idle. All seem ok for AAC.

Then I checked the timing and adjusted it w/ the TPS disonnected, set it to 20 degrees. The motor hovers around there when its idling and happy.

I'm running copper 6 plugs, at 1.1 gap. I know thats a bit high, but I'm just trying to get this thing to idle so I can properly break in the motor.

The motor isn't knocking, b/c I've disconnected the knock sensors, and I get the same deal. Plus I never rev it enough to even pull atmospheric, so my cylinder pressures cant be that high.

Running PFC with 550cc injectors, have them dialed in. Running 2 RB25 MAFs, have those dialed in as well.

I'm going to buy some suff to pressurize my intake stream from the mafs all the way to the throttle plate to see if I have any leaks. I've triple checked everything, no vac leaks. I get good vacuum at idle.. between 10-15 in Hg. When I pull one of the vacuum hoses (FPR or BOV), the motor ramps up to compensate just fine.

Questions/potential issues:How important is the idle switch? (the one attached to the TPS unit)Mine is broken, according to PFC. I've hot wired it so that it "works" and PFC is seeing that I want to idle. However, when I disconnect and reconnect it, it doesnt do a damn thing. Miraculously, my TPS still works. I have it set between .4 closed - 4v wot.

How important is the air regulator? I just got that thing wired in, I give it IGN signal basically. It didnt seem to do crap for me.

Only thing I can think of is my TPS unit is screwy...
Modified by gawdzilla at 10:37 PM 10/15/2005

[scottsi]

im gonna have to say its probably the tuning, and 10-15vac sounds kinda low imo, but hey whatta i know

[eh?]

how does it rev without the TPS plugged in? Is your idle at 10-15mmHG or 10-15PSI? It's either too low or way too high.

[Yellow4g63]

dose it run ok other than the idling? what about the CAS do you have another one you could try?

[gawdzilla]

sorry it is 10-15 inches Hg.

the motor IDLES fine as long as I don't mess w/ it. once i start revving it, it climbs up ok, but when i let off the throttle the motor goes nuts, like it cant stabilize again. then when i try to hold a steady throttle it sounds as if im jerking the throttle back and forth until it cuts out. The AAC is trying to catch the motor, but it seems like its reacting too slow.

[eh?]

normal vac is about 17-20 mmhg.

[gawdzilla]

would turbulence around the MAF area cause the motor to run rough like it is? I am running open MAF right now, so it is extra sensitive.

[Valley]

last i checked, if the CAS wasn't sending signal on one or both 1/120 degree's then the car won't start period.

what is the a/f ratio when it starts messing up?

[Bluefire]

do a boost leak check first.... get a squirt bottle with some soapy water and squirt every connection on the motor.

-Bluefire

[gawdzilla]

normal vac is about 17-20 mmhg.

you sure about that? basically you're saying you idle at an NA engine's WOT? I think you mean inches Hg. 17-20 mm Hg is practically nothing. basically no vacuum at all.

im gonna check for piping leaks tomorrow.

[eh?]

yes inHG sorry get confused

[gawdzilla]

ok, i pressurized my intake tract from the turbo inlets on. found two small leaks in my piping, and my bov vacuum was leaking a tiny bit. solved those problems, then started it up again.

I get about 17 in Hg vacuum.

similar problem, lots of weird hesitation followed by motor dying.

would turbulence around the MAFs cause this problem? I am running filterless and the maf element is pretty close to the opening.

[Yellow4g63]

try and put some card board to block any air comming from your fans. The MAF is sensative to air flow without a filter but I don't know if thats your problem. Give it a try tho.

[Yellow4g63]

last i checked, if the CAS wasn't sending signal on one or both 1/120 degree's then the car won't start period.

what is the a/f ratio when it starts messing up?

Not really, My friends CAS was bad on his RB25. Car started fine, idled like normal but kill power all over the board on his car. Changed the CAS and power was back.

[onefastrb26]

Please give me some suggestions on making my motor run right! ok, so heres the deal.

start the motor, it always starts up right away. Get good oil press, etc. etc. idles fine, goes to about 950 rpm like the FSM says (rb26). When I rev it a bit, slowly, it can rev up and crawl to an rpm. When I start moving the throttle (letting off and getting on it), the motor starts getting weird on me. It pulls timing like the motor is knocking, and the rpms bounce up and down while the motor is compensating to catch itself. It seems like it is reacting too slow or something, between bogging and running too high for an idle. When that starts, I cant hold a steady rpm anymore, the motor sounds SUPER hesitant on the verge of death, and the motor eventually dies and cuts out.

Things I've done:i adjusted the idle via the screw w/ the AAC plug off, at about 950 rpm. I know the AAC is working cuz when I unplug it the motor ramps up. I took it off yesterday to clean it, checked the ssolenoid, and also read the voltage across it while the motor is running. Voltage crawls up slowly as the motor warms up, and while its going kinda crazy, the voltage is jumping around so the AAC is trying to catch my idle. All seem ok for AAC.

Then I checked the timing and adjusted it w/ the TPS disonnected, set it to 20 degrees. The motor hovers around there when its idling and happy.

I'm running copper 6 plugs, at 1.1 gap. I know thats a bit high, but I'm just trying to get this thing to idle so I can properly break in the motor.

The motor isn't knocking, b/c I've disconnected the knock sensors, and I get the same deal. Plus I never rev it enough to even pull atmospheric, so my cylinder pressures cant be that high.

Running PFC with 550cc injectors, have them dialed in. Running 2 RB25 MAFs, have those dialed in as well.

I'm going to buy some suff to pressurize my intake stream from the mafs all the way to the throttle plate to see if I have any leaks. I've triple checked everything, no vac leaks. I get good vacuum at idle.. between 10-15 in Hg. When I pull one of the vacuum hoses (FPR or BOV), the motor ramps up to compensate just fine.

Questions/potential issues:How important is the idle switch? (the one attached to the TPS unit)Mine is broken, according to PFC. I've hot wired it so that it "works" and PFC is seeing that I want to idle. However, when I disconnect and reconnect it, it doesnt do a damn thing. Miraculously, my TPS still works. I have it set between .4 closed - 4v wot.

How important is the air regulator? I just got that thing wired in, I give it IGN signal basically. It didnt seem to do crap for me.

Only thing I can think of is my TPS unit is screwy...

Modified by gawdzilla at 10:37 PM 10/15/2005

Datalog tps voltage and airflow % usage. See if anything weird is going on there...Also, what 550cc do you have - low or high impediance? Do you have the resister pack?

Did you try the same scenario with stock RB26 mafs?

[gawdzilla]

i dont have datalogit unfortunately, nor the rb26 stock mafs. motor didnt come w/ them.

my tps voltage ranges from .5-4v, fully closed and WOT.

Does the idle switch being on make a big difference?

Nismo 550cc's pink tops, they are low impedance and yes, i'm using a resistor pack (well 2 of them cuz I'm using 2 4 cyl ones)

ALSO: has anyone had experience w/ turning o2 feedback OFF with PFC? I've turned it off b/c my o2s are fouled (never get less than 1v across them)... still get the hesitation crap.

[onefastrb26]

My O2 feedback is off, and everything is fine.

Without a datalogit it will be really hard to diagnose it.

i dont have datalogit unfortunately, nor the rb26 stock mafs. motor didnt come w/ them.

my tps voltage ranges from .5-4v, fully closed and WOT.

Does the idle switch being on make a big difference?

Nismo 550cc's pink tops, they are low impedance and yes, i'm using a resistor pack (well 2 of them cuz I'm using 2 4 cyl ones)

ALSO: has anyone had experience w/ turning o2 feedback OFF with PFC? I've turned it off b/c my o2s are fouled (never get less than 1v across them)... still get the hesitation crap.

[gawdzilla]

My O2 feedback is off, and everything is fine.

So you're saying that PFC will ignore the o2 readings when this function is selected?

[Wulfgang]

I dunno... your symptoms have all the telltales of a MAF problem. And yes, turbulence can screw up the reading. Try just sticking a cone filter on there temporarily to see if that clears it up. If not, block off one turbo and MAF (open the wastegate) and check each MAF separately for correct operation. Obviously you won't want to rev too high with one turbo spinning freely....

[goofynick6]

Hey, Surpised nobody mentioned it, but yes, the idle switch makes a difference. When mine wasn't wired in the the car idled funny and I had to readjust it a bit to get it to idle normal. However, once I got it working, the car idled normally and it didn't stall out everytime I revved the car. That tells the car it is no longer being revved and opens the idle control valve the proper amount to prevent stalling and to maintain proper idle. Also, the neutral switch needs to be wired in if it isn't; that helps with idle as well.

Good luck,Nick

[gawdzilla]

Thanks for the tips guys. I'm currently converting over to the standard o2 sensors instead of the weird GTR-only ones. once that gets taken care of i'll play w/ the tuning a bit more.

[gawdzilla]

for those running PFC with a different MAF...when you set the MAF in the settings, do you need to do anything in the "next" window? Its the window with all the voltages and the percentages. why are they all the same for all the MAFs???

[onefastrb26]

for those running PFC with a different MAF...when you set the MAF in the settings, do you need to do anything in the "next" window? Its the window with all the voltages and the percentages. why are they all the same for all the MAFs???

Yes, the PFC will ignore the O2 readings if you disable the O2 feedback.

If you select the bigger MAFS, it automatically chooses the voltages and percentages. But I have not done a GTR with a Ljetro and big mafs yet. I have tuned several GTRs with Djetro PFCs, and they were pretty smooth.

I am tuning my car with the original Apexi FCPro software, not a dataloggit or commander. Here is the screenshot of the MAF table for your car. At least you can compare the values.

[gawdzilla]

on the commander, it shows about 6-8 voltages.. varying from 1.x volts to 4 or 5 volts, and a percentage for each.

When i look at each MAF, the settings look to be the same regardless of rb26 standard, r33 rb26, z32, rb25, etc.... are they not preset for you to use?

[onefastrb26]

on the commander, it shows about 6-8 voltages.. varying from 1.x volts to 4 or 5 volts, and a percentage for each.

When i look at each MAF, the settings look to be the same regardless of rb26 standard, r33 rb26, z32, rb25, etc.... are they not preset for you to use?

Yes, the voltage screen is the same , but the air flow screen is different for each sensor. The one I showed you was for a RB25.

Is your PFC brand new? Where did you get it from?Where do you live?

[gawdzilla]

PFC is used, all i have is the controller for now.

i live in Maryland, near DC.

I can't seem to get to that screen with those numbers you posted... is it only available in the tuner software?

Hit me up on AIM if you use it... easier to disuss this, thanks.
Modified by gawdzilla at 2:40 PM 10/19/2005

[gawdzilla]

The car is getting much better now. I've got the narrowband o2s in, and noticed it was running pig rich. I leaned out the maps a little bit, and it actually enters closed loop now. I can rev it around a bit and it will catch MUCH better.

It still gets rough on me, but now I know its the fueling map.

[onefastrb26]

The car is getting much better now. I've got the narrowband o2s in, and noticed it was running pig rich. I leaned out the maps a little bit, and it actually enters closed loop now. I can rev it around a bit and it will catch MUCH better.

It still gets rough on me, but now I know its the fueling map.

What wideband do you have in the car?

You can trim the overall fuel map, too....

[gawdzilla]

i don't have a wideband right now, but the bung for it is already in my downpipe. I'm tuning based on my narrowbands, going very slowly.

The isnt under any load, and i'm only revving to about 2.5k, so I figure it is ok. I cant change the entire map quite yet, doing the first 5x5 group of cells under the injection maps right now.

WHY is the stock map so damn rich?

Thanks
Modified by gawdzilla at 12:12 AM 10/22/2005