Dies while letting off the gas (not just after boost)

[ppctx]

http://www.youtube.com/v/HH_TQrtTI5ICar idles a little rough when warming up, idles fine (900rpm) once warmed up, but after that it dies while driving (not in boost) when letting off the gas to shift gears. I can restart and it idles fine but will die again after driving and letting off the gas. This is with or without getting into boost and it’s recirculated anyway. It also studders a bit (like I'm pulsing the throttle while driving). Pulls great at WOT but again dies when letting off gas to shift gears.

S13 ka24det Enthalpy ECU 480cc DW injectors N62 (z32) MAF t3\04 plugs gapped at .031 removed SAFC to diagnose problem (still dies) open exhaust emissions removed Using PLX wideband O2 sensor and outputting narrow band signal to ECU with it This worked fine while NA A\F ratio during die time is 14.5 +/-1

ANY THOUGHTS... leaky injectors, crapped tps sensor, thermostat out, bad ground, anything,?

I'm fairly bummed about this as this is after finally getting it on the ground after 9 months on jack stands… thought I had every thing perfect
Modified by ppctx at 11:00 PM 5/9/2008

[480sx]

I had the same problem too, its pretty much fixed after i bumped up the idle per Scott's(enthalpy) advice. It will still do it when i drop from WoT tho(open bov+MAF ftl). It still takes some care to not stall it, im sure i could turn the idle up even more and it would go away. However i dont want my idle any higher than it already is. Cruising around town though it catches the idle perfectly.

Just take a philips head screw driver and adjust the IACV screw out. I put my idle IIRC at about 1000, idles at about 1200 when cold. When adjusting it, be really careful if you have a S14 motor. The screw itself is PLASTIC(WTF NISSAN), instead of the metal one in the s13's.

[ppctx]

900rpm isn't that far off from 1000rpm (but I'll crank it up a bit) and it dies like I turned off the key, no hesitation or trying to stay started. Strait from what ever rpm to 0, kind of like the dist was unpluged

[DevilMB3017]

Scott @ Enthalpy told me two things when I had this problem.

1) Make sure your recirc'ing your BOV, but everyone will agree with this.

2) Move your MAF to be at least 12-16 inches away from the turbo, and with a couple bends in the piping.

You'll see bigger results from number 1.

[ppctx]

With a JGS mani, I could only get the maf ~6" away from the turbo. The BOV is recirculated but may not be functioning properly, per reply on another forum. Will post some pic's of my bay this evening.

[ppctx]

Here are some pic's of the bay. Let me know if a closer shot of anything would be helpfull. No making fun of my TEMPORARY attic inslulation/heat shield or the ribbed for her pleasure recirculation hose!

[C-Kwik]

Getting the MAF further from the BOV return line helps, but what might also help is to angle the hose at the turbo more. You might consider having a new tube made to relocate the MAF into a vertical position closer to the filter or perhaps bending towards the corner of the engine compartment. Of course, the latter would likely require a flatter filter.

But bbefore you start replacing parts try making sure all your hose connections are tight. A loose connector in a pressurized portion of a pipe can cause similar smptoms as a non-recirulated BOV. Bear in mind these can also be hard to find as the connector still may be in place while the air simply escapes between the pipe and the connector itself. I had this issue once and it took me some searching to locate the leak.

[Craving4Boost]

clean install Aaron! you've come a long way. No one better hate on that recirculating hose because it took me a long time to find it lol. Anyways you have 2 options:

Make sure you enable the Dec-air settings on the SAFC. I enabled it and I never ever stalled even with going from Wot to neutral. For your info, my settings were as follows:

Thr% - 2%NE1 - .7NE2 - 1.7

IN ADDITION, I lowered my TPS voltage from .49V AT CLOSED to .41. man i do not know why this fixed it...but it did. You'd think .08 wouldn't do **** but let me tell you, I used the same dec-air settings with it at .49V and it still stalled.

For your studdering issues, I had the same problem...wasn't that big of a deal. I've heard a new TPS (around 80$ i believe) wil help greatly. Also, not calibrating your TPS to .49V at closed will also create sputters throughout at low cruising speeds. But like I said, I went with .41V and although I get more sputter, the no stalling out was well worth it.

Looks like you've learned a lot. Maybe I should call you up and give you an exam and test ya

[Craving4Boost]

Oopz sorry I didn't tell you about your second option. That is, of course, to go with a blow through MAF set up. That is, instead of having the MAF sensor before the turbo, have it after the turbo. Some people have had success...some people have had failures...join one club one way or the other.

[480sx]

Some serious rigging you got goin on there man! I love seeing dudes ka-t setups.

Gotta tell you though man, that insulation is fire resistant not fire proof. I mean your turbo is far enough away from the BMC as it is, you can get rid of that stuff all together. Also, your DP is heat wrapped and thats gona cut down on the radiant heat in that area tremendously. The brake lines are the only thing i can see that might be a problem and that wad isnt covering them.

I still think your problem can be fixed by bumping up the idle to 1000-1100. I think mines actually higher than i thought, i remember the needle being above the 1000 line a little bit.
Modified by 480sx at 6:58 PM 5/7/2008

[Craving4Boost]

regardless of how you set your idle via IACV, TB plate, etc....it will not hold it when boosting and harshly throwing into neutral. And for people who just give it some gas so it wouldnt die....try that in San Francisco and you'll run right into a car. You need to find an alternative that will let you brake suddenly without worrying about your idle dying and then your brakes are crapped out cause your engine isn't running.

[480sx]

On a turbo charged car the throttle plate bypass has to work extra hard to get air through the turbo when its not spooled(at least this is my theory as to why allowing the IACV to move more air got my car drivable again, when i had this exact same problem). The IACV was designed to work at atmospheric pressure, and i would imagine that there is a slight vacuum on the IC system at cruising speeds.

Hes recirculated man, he shouldnt have any problems thrashing the car and letting it idle down. Were not talking about the normal stalling due to VTA bov's, were talking about daily driving conditions here.

Im just sayen, i had this exact same problem and fixed it by simply bumping up the IACV a considerable amount.

[ppctx]

Could it be the Enthalpy ECU? Previous owner of had the same stall issues. More info. It idles fine when warmed up but if you give it a little gas then let off, the wideband reads LEAN then it dies and. While parked, I can keep it started by feathering the gas back down to 1000rpm but "slightly" goose it and let off > LEAN > stall????? Please help!

The TPS reads 8.86k ohm when close (fsm says it should be ~10k ohms? I wouldn't thik that'd be enough to kill it) temp sensor reads perfect disconecting the O2 sensor has no positive effect on stall various gound to chassie, mani, ect test points read great (< 0.5 ohm resistance)

Modified by ppctx at 10:55 PM 5/7/2008
Modified by ppctx at 11:50 PM 5/7/2008

[Craving4Boost]

Enthalpy can't really do anything with a tune. And even if he could, it's something that he can't do with a mail-rom tune. your reading lean when you let off probably because your recirculated. It would be rich otherwise.

[esahuque]

Could it be the Enthalpy ECU? Previous owner of had the same stall issues. More info. It idles fine when warmed up but if you give it a little gas then let off, the wideband reads LEAN then it dies and. While parked, I can keep it started by feathering the gas back down to 1000rpm but "slightly" goose it and let off > LEAN > stall????? Please help!

The TPS reads 8.86k ohm when close (fsm says it should be ~10k ohms? I wouldn't thik that'd be enough to kill it) temp sensor reads perfect disconecting the O2 sensor has no positive effect on stall various gound to chassie, mani, ect test points read great (< 0.5 ohm resistance)

Modified by ppctx at 10:55 PM 5/7/2008

Modified by ppctx at 11:50 PM 5/7/2008

Its supposed to go lean on decel. even n/a goes lean on decel, its Nissan way of saving gas. its when it goes rich on decel, thats what usually makes it back fire and stall. if its going lean on decel its not in your tune, your tune is working right. try seafoaming your acc valve and do a boost leak test.

[ppctx]

http://www.youtube.com/v/HH_TQrtTI5IHopefully this works as it’s my first time to upload vid to the web. First stall shows the tach and boost gauge sitting at -20, the second stall show the tach and wideband. The only time I give it gas is when you see the rpm’s stable at ~1000rpm then I gave it a little throttle. No throttle given to start or prevent stall.

Setting decel on the SAFC did not help Voltages check out fine on the TPS
Modified by ppctx at 11:01 PM 5/9/2008

[Craving4Boost]

maybe you should loosen the BOV more to get that recirculation into drive more. Loosen the nut on top of the BOV and I believe you can stick in a allen key and turn it too 'soften' it. See if that works.

And also, kind of a bad place for the wideband don't you think Aaron? I personally had it on the steering column in front of the RPM where it could be seen better.

Nice idle and AFR's though..once you cure this stalling..you'll be set.

[Craving4Boost]

Also try playing with the del air settings on the SAFC as well. maybe go for .6 / 1.6 as opposed to .7 / 1.7 . It took me a while playing with those numbers to finally get it right. But try and see if it at least has any affects.

[ppctx]

Thanks Steven. I did try the decel after talking with you the other day, didn't have any positive effect, I'll play with it some more. I used the BOV as you gave it to me, then tried tightening it... I'll try loosening it up.

Blew degreaser down the IACV line... didn't help

I have another theory I'll try when I get home.

[Craving4Boost]

You should tighten it if it leaks to much during atmospheric ventilation. But it's ok if it leaks a little if you recirculate it IMO. Just see if it affects anything first because I don't even see your AFR's changing much when you were revving in neutral.

And also, is your wife getting pissed off your spending so much time on the car? lol I can only wonder..

[ppctx]

I wouldn't know how mad she may be, she's usually in bed by the time I get done working on the car and internetting for solutions

I was curious how much unmetered are was entering the intake via the valve cover being vented so I put a plastic baggy on the filter and twisty tied it on. To my surprise it sucked harder an a crack whore. Interestingly enough, instead of my a/f richening up, it leaned way out during idle. When I turned the car off, the vacuum remained so I'm going to look into my pcv set up.

[ppctx]

Two questions. Could it be an O2 sensor issue or a MAF issue. When I unhook the MAF, It idles like crap but can not get it to die. The O2 seems suspect because I will get different readings at different times. Sometimes it read super rich, sometimes spot on then sometimes super lean. I am using the PLX wideband to output a narrow band signal to the ecu, been told and have read that this can cause issues?

Let me know what you think. As you know it's not fun cutting/splicing the ecu harnes, expecially multiple splices if these probably aren't the problem.

the PCV system is hooked up good (but its still intresting that the valve cover sees so much vac an thus unmetered air)

[ppctx]

Well its not the ECU. Put the stocker back in and used the SAFC to cut fuel. Idled a little richer but stalls just the same.

Im starting to lean toward it being the idle control. I cant get it to idle any faster than 900-1000 rpm. Gets there with just a little turning of the screw, then levels out there, even if it is turned to max high.

[Craving4Boost]

unplug the TPS and adjust Idle. If it still has no effect, then something is wrong with it.

[ppctx]

Unhooking it lowers it a bit and the on voltage and off resistance are "close" to spec. I removed the IACV this evening, will test, clean and reinstall tomarrow. Cross my fingers, pray, anything, I'm running out of things that it could be.

Please dont hesitate to throw posibilities my way.

[esahuque]

Using your wideband as your O2 signal will cause problems. you need to put your stock O2 back in and have your wideband as a stand alone. That is probably not your whole problem but its definitely not helping it any. I battle rough and dipping idle for almost 6 months before i figured out that my wideband as an O2 was causing it.

[24DSXY1]

Would this work:HKS EIDS TYPE H-1(Electronic Idling Stabilizer)The HKS EIDS has been developed to buffer dramatic airflow meter signal fluctuations. By buffering these fluctuations the EIDS prevents engine stalling or stumbling associated with sudden imbalances in air/fuel ratio of airflow meter-equipped vehicles that utilize atmosphere venting blow-off valves.

go to optauto.com>forced induction>blow off valves>nissan

[ppctx]

I'll definatly look at the EIDS (but I am recirculated).

I'm changing over to an adjustable FPR this weekend. If that doesn't get it, I'll wait till the pipes cool down and throw the stock O2 back on (only have one bung at the moment, so wont be able to monitor a/f for that test)

Got an email into Enthalpy and waiting on a responce...

[ppctx]

Scott @ Enthalpy told me two things when I had this problem.

1) Make sure your recirc'ing your BOV, but everyone will agree with this.

2) Move your MAF to be at least 12-16 inches away from the turbo, and with a couple bends in the piping.

You'll see bigger results from number 1.

Scott at Enthalpy rock (and knows his ****e) Move the MAF away from the turbo and problem solved)

[480sx]

Yea Scotts a good guy, def knows his stuff. Glad you fixed your problem man. happy boostin