KA24DET rich bogging/stalling on decel, not catching idle

[Chugpuppy]

Hey guys, need some help here

I've had this problem ever since I was N/A, although it was a LOT less pronounced than it is today. Basically, when the engine warms up and the idle settles at its normal operating rpm (around 800ish, with 15 afr), letting the rpm drop from anywhere above ~1500 rpm causes the engine to drop past 800 rpm and die. When it drops like that I'm getting readings of ~10 afr (maybe lower, the UEGO sometimes takes a while to register really rich conditions, and only reads down to 10). Sometimes it will catch itself, bounce up and down for a couple seconds, then even out, but nowadays it usually just bogs out and leaves my wideband reading a solid 10.

The second symptom is rich throttle transition. When I feather the throttle (just baaaarely giving it gas) it causes it to run really rich, again sweeping the wideband to a 10. It seems to hesitate when I get on the throttle also. If I'm in a parking lot or something, and have a jerky start (350z pp and 6 puck rated for 500hp, what) if my foot accidentally bounces on the throttle it will jerk VIOLENTLY, causing my foot to hit the throttle more, which makes it worse. I have to clutch in at that point, while also holding the gas so it doesnt die, then slip the clutch a little to get going smoothly again.

This also happens in second, and to a lesser degree in the higher gears. If i get off light throttle, then get back on in quick succession, it'll jerk roughly. Pisses me off. It especially likes to happen when I'm cruising at low speeds, but just barely need to touch the gas to keep myself going. Goes really rich when it does this, and will afterfire if I get back on throttle.

Everything besides throttle transition and idle is fine. Feels a little sluggish at wot, but pulls good afrs.

TL;DR: Once warmed up, car dies when clutch is pushed in and rpms drop, wont catch itself at idle. Throttle transition sucks, jerks around a lot. In both of these situations it goes really rich, with afr @ 10. Fine afrs under constant accel.

EDIT: car is also hard to start when warm. cranks fine, but doesnt catch unless i fiddle with the ignition and give it gas.

Now, mods and diagnosis:
S14 KA
S13 harness, coil, distributor, etc
Most of the Greddy 20g kit
Z32 MAF
440cc injectors
Enthalpy tune

What I've done recently to solve it:
Boost leak tested at ~25 psi, didn't hear any obvious leaks
Pulled codes, found 34, 12, 13
Cleared codes, 34 and 13 still showing up
Wired in a resistor to emulate a knock sensor, as my KS wiring circuit is bad. Resistor brings signal from ECU down to 2.05v, no more code 34.
TPS adjusted from .44v closed to .5v closed, currently reads .5v closed 4.35v open
Pinched and disconnected fuel pressure regulator vacuum line, no change in idle?
Disconnected MAF and started car. Idled lower, ~500, but still dropped a little when I let the rpms fall.

What I think may be wrong:

Bad MAF wiring/grounds - I'm not sold on this one though. The fact that it still did it with the MAF unplugged makes me think it isn't related.

Bad coolant temperature sensor - A possibility, although I wouldn't think it would cause this serious of a problem. Still have code 13, popping in a new one tomorrow.

Bad fuel pressure regulator - This is my new target. It worries me that it doesn't change the idle when I pinch or disconnect the vacuum line. I'm thinking maybe the diaphragm inside is sticking? or caught? Could be holding it at a pressure level suited for being on-throttle even when it goes back down to idle, causing extra fuel to be injected and it to bog down.

I can get pictures and video of my setup if that'd be of assistance.

I've been dealing with this for like a year now though, and any help would be appreciated :hs: so fed up with this car, missed a fucking awesome Dspot event with the Tuercks and Drift Faction guys today because I thought I could have it fixed once I pulled the codes, but nope...

[Chugpuppy]

54 views and not a single comment... cmoooon

[ultimateirving]

Kas have an iacv right? If that's the case test and replace. I had major issues with dying at decel and my idle would surge between 600-1300. Got a new iacv and it fixed all my idle decel issues

[Chugpuppy]

Kas have an iacv right? If that's the case test and replace. I had major issues with dying at decel and my idle would surge between 600-1300. Got a new iacv and it fixed all my idle decel issues

Took out IACV and cleaned it up, thing was spotless when i put it back in. No change :/

[drifting1two40]

i have a 93 ka24de with deleted emissions and egr blocked off. charcoal canister deleted. headers test pipe and catback. cold air with a 3 angle valve job all the valve seals replaced and arp head studs...ive been doing all this modification so that after i fininsh collecting my pieces im going ka-t.

but im trying to get my car running A1 before i boost so that i dont have the same problems transfer over once i turbo.

Well my ecu has the ECT code as well and a couple others. Basically my car runs pig rich and i have started to notice my oil getting black faster than usual and smelling of fuel lightly.

but two days ago i was looking at my ECT connector on the harness side and noticed theres was green corrosion all inside of it. also it didnt have the metal retainer holding it in place. so since i work at a nissan dealership i basically made a new connector with new metal contacts and everything on the inside and a new retainer now it seems im getting better gas milage and my exhaust doenst smell of fuel, or my oil. just my two cents about my ECT experience

[ultimateirving]

Took out IACV and cleaned it up, thing was spotless when i put it back in. No change :/

Have you tested it to see if it functions? because this part specifically is designed to hold idle and catch the rpms from dropping too low and dying.

[Chugpuppy]

i have a 93 ka24de with deleted emissions and egr blocked off. charcoal canister deleted. headers test pipe and catback. cold air with a 3 angle valve job all the valve seals replaced and arp head studs...ive been doing all this modification so that after i fininsh collecting my pieces im going ka-t.

but im trying to get my car running A1 before i boost so that i dont have the same problems transfer over once i turbo.

Well my ecu has the ECT code as well and a couple others. Basically my car runs pig rich and i have started to notice my oil getting black faster than usual and smelling of fuel lightly.

but two days ago i was looking at my ECT connector on the harness side and noticed theres was green corrosion all inside of it. also it didnt have the metal retainer holding it in place. so since i work at a nissan dealership i basically made a new connector with new metal contacts and everything on the inside and a new retainer now it seems im getting better gas milage and my exhaust doenst smell of fuel, or my oil. just my two cents about my ECT experience

Going out to replace the coolant temp sensor now... I'll let you know if it changes anything

[silviaks2nr]

unplug your iacv from the harness and see if it runs any differently. My car runs 100% perfect with it unplugged so I just leave it off. Is your bov vented? if so can you stiffen it or recirc it? Shitty alternator/battery/grounds can cause symptoms like this as well. It would also be a good idea to change out the plugs if it's having warm start issues.

when you boost leak tested it did you open the throttle body?

[Mitsubayati]

I didn't read through the whole thread, but I had that same idle drop issue you had. It turned out that I needed to replace my distributor cap. The contacts were corroded. When I replaced it, the car idled perfect and I actually had more noticeable power as it had diminished.

[drifting1two40]

i would check the resistance on the sensor first before you just replace it. because mine wasnt the sensor . just the connector on the harness wasnt getting good contact

[Chugpuppy]

Coolant temp sensor replaced, getting code 55 on the ECU so electronically things are looking OK. Letting her cool off then taking her out to see if it made a difference.

[Chugpuppy]

unplug your iacv from the harness and see if it runs any differently. My car runs 100% perfect with it unplugged so I just leave it off. Is your bov vented? if so can you stiffen it or recirc it? Shitty alternator/battery/grounds can cause symptoms like this as well. It would also be a good idea to change out the plugs if it's having warm start issues.

when you boost leak tested it did you open the throttle body?

I'll try unplugging the IACV next. BOV is atmospheric, but I dont think that's the problem. Only running like 7lbs of boost. I have a grounding kit installed, so grounds should be good, and I had the battery and alt checked out not too long ago, but it wouldn't hurt to double check. Just changed the plugs recently, so I'm gonna leave em in til I can get this figured out

[silviaks2nr]

I'll try unplugging the IACV next. BOV is atmospheric, but I dont think that's the problem. Only running like 7lbs of boost. t

Even if you're only running 7psi if it's soft enough that it's open at idle you are going to basically have a very large vacuum leak and the car can idle down and run poorly under part throttle and when transitioning from vacuum to boost. I guarantee this is at least part of your problem.

[Chugpuppy]

Even if you're only running 7psi if it's soft enough that it's open at idle you are going to basically have a very large vacuum leak and the car can idle down and run poorly under part throttle and when transitioning from vacuum to boost. I guarantee this is at least part of your problem.

It's not open at idle, spring's pretty hard actually. I still get a little flutter. Also, it's bogging down because it's running rich, if it was allowing air to get in it would be running lean afaik. I'll crank it all the way hard just to make sure though.

[Chugpuppy]

UPDATE: New engine coolant temp sensor in. Not getting any more codes. Car runs more or less the same :/ maybe a little less rich and more predictable while driving, but still exhibits the same symptoms as before.

I unhooked the BOV so it doesn't open at all, car still wanted to die when rpms dropped back down from revving it, so that isn't the problem.

When IACV was unhooked the idle dropped to ~400. Car still stalled after being revved to ~2500.

[Chugpuppy]

Bored at work bump. Thinking about replacing FPR soon.

[Chugpuppy]

Bump before I order a new FPR

[BryanS14]

I am having almost the same issue to a "t", I am thinking FRP too, mine is noisy at time. Not sure if I will have it replaced within the next week, so ill be looking to see if that fixed it.

[s13drob]

I saw your link in another similar thread. I think you should do the same as i suggested on his issue. Check base timing/idle...
KA-T.org - The Home of 1000+ whp/7 sec Turbo KA's (http://www.ka-t.org/dohc_basetiming.php)

[Chugpuppy]

I saw your link in another similar thread. I think you should do the same as i suggested on his issue. Check base timing/idle...
KA-T.org - The Home of 1000+ whp/7 sec Turbo KA's (http://www.ka-t.org/dohc_basetiming.php)


First thing I did. Right on the money.

Ordering a new FPR today when I get home from work. *pretty* sure that's what it is. All the symptoms point to it. Just not sure whether or not to just get a replacement stock or go adjustable aftermarket...

[Chugpuppy]

New Borg Warner stock replacement FPR installed along with new Z32 fuel filter. No change. Checking MAF voltages again tomorrow and adding a chassis ground. Running out of ideas.

[tayloray]

holy shit this is a though one. Have you checked you're tps voltage? Granted that would be cutting fuel rather than adding, but i've had issues with mis-calibrated tps's, and it does that on-off throttle bobble. The tps was still reading 0 at part throttle. Not sure if it'll help, but just throwing an idea out there.

[Chugpuppy]

holy shit this is a though one. Have you checked you're tps voltage? Granted that would be cutting fuel rather than adding, but i've had issues with mis-calibrated tps's, and it does that on-off throttle bobble. The tps was still reading 0 at part throttle. Not sure if it'll help, but just throwing an idea out there.

Yeah, I'm trying to cover everything. TPS has been checked and adjusted to spec, was .44v closed, increased to .5v closed with no change. 4.35v WOT.

[tayloray]

Have you checked your injector o-rings? I had issues with them going out and causing vacuum leaks. As well as them causing fuel to pour past the injector into the cylinder.

[Chugpuppy]

Have you checked your injector o-rings? I had issues with them going out and causing vacuum leaks. As well as them causing fuel to pour past the injector into the cylinder.

I have a top mount injector setup and Greddy rail, so that can't really happen afaik... My engine is bogging because of a rich condition, not a lean one that could be caused by vacuum leaks.

Checking voltages and rechecking timing when I get home from work. Could it be possible that the distributor is off a tooth, and even though it's at the stock 20 degrees it could actually be advanced or retarded?

EDIT: I shot it with a light and the timing was at 20*... so it should be perfect correct? If the dist was off a tooth, therefore skewing timing, shouldn't the light catch that?

[tayloray]

I have a top mount injector setup and Greddy rail, so that can't really happen afaik...

Checking voltages and rechecking timing when I get home from work. Could it be possible that the distributor is off a tooth, and even though it's at the stock 20 degrees it could actually be advanced or retarded?


Oh yeah duh. Forgot ka's where top feed. You could still get and injector leak but you would definitely hear it.

If timing was off it wouldn't run well at all. It would still idle alright too.

Checked your intake manifold gasket?

[Chugpuppy]

Oh yeah duh. Forgot ka's where top feed. You could still get and injector leak but you would definitely hear it.

If timing was off it wouldn't run well at all. It would still idle alright too.

Checked your intake manifold gasket?

KA's are side feed stock. I converted mine to run RC Engineering 440cc top feed injectors.

Intake manifold gasket was recently refreshed with a new Felpro one, which resulted in no change. The intake system from the turbo to the block has also been tested to 25lbs of pressure and no obvious leaks were present. Again, the car is dying due to a rich condition, not leaning out as would indicate a vacuum/boost leak.

[tayloray]

KA's are side feed stock. I converted mine to run RC Engineering 440cc top feed injectors.

Intake manifold gasket was recently refreshed with a new Felpro one, which resulted in no change. The intake system from the turbo to the block has also been tested to 25lbs of pressure and no obvious leaks were present. Again, the car is dying due to a rich condition, not leaning out as would indicate a vacuum/boost leak.

Have you tried letting it die then checking your plugs? Could have a bad injector that's sticking open. Flooding out one cylinder.

[Chugpuppy]

The plugs don't really change color, but I can see a little puff of black smoke when it dies. If one injector was sticking open it'd run weird during accel and also idle weird. It idles perfectly, but dies if it's revved and then not given gas after.

[tayloray]

The plugs don't really change color, but I can see a little puff of black smoke when it dies. If one injector was sticking open it'd run weird during accel and also idle weird. It idles perfectly, but dies if it's revved and then not given gas after.

I know someone already mentioned this. But I had the same problem with my old rb20 setup. Turned out to be a leaky bov. Which may make sense because if you rev, start to build boost then release, you loosing metered air. Causing a rich condition. Have you tried a new maf?

[Chugpuppy]

I know someone already mentioned this. But I had the same problem with my old rb20 setup. Turned out to be a leaky bov. Which may make sense because if you rev, start to build boost then release, you loosing metered air. Causing a rich condition. Have you tried a new maf?

Disconnected the vac line and covered the BOV so it didn't open, still no change. Not the BOV. I haven't tried a new MAF yet, but I will this weekend. Problem is, this started (albeit it was much less serious) before I was turbo, when I had a stock KA with the stock MAF. Current Z32 MAF has been cleaned multiple times with MAF spray cleaner.

[tayloray]

Yeah I know what you mean. It just can't really be anything else. There's only so much that controls fuel

[c-los13]

i actually read your whole thread
i had 2 friends w the same problem
"ka-t's dying when after the left off the gas"
they both went with a different kinda tune since the never figured it out, one of them even tried for a whole year :smash:
they both got a "blow through" setup and theyre problems were gone!
it was actually done by Enthalpy (again, Martin is awesome)
I know many ppl is done without going that route but at least my 2 friends couldnt.
just my .02

[tayloray]

Maybe the injector driver in your ecu is going bad and not shutting off the injectors when you let off the gas like it should?

[Chugpuppy]

i actually read your whole thread
i had 2 friends w the same problem
"ka-t's dying when after the left off the gas"
they both went with a different kinda tune since the never figured it out, one of them even tried for a whole year :smash:
they both got a "blow through" setup and theyre problems were gone!
it was actually done by Enthalpy (again, Martin is awesome)
I know many ppl is done without going that route but at least my 2 friends couldnt.
just my .02

I've been trying to figure it out for close to a year haha. I'm thinking it has to do with either the MAF wiring, or a vortex effect created by the turbo that's causing the MAF to read incorrectly. Checking voltages tomorrow.

Just sending the ECU in to get tuned for blow-through would be easier though.

Also, I tested the idle air controller systems today by unplugging the IACV/AIV/that other one and blocking off the IACV air feed. Cracked the throttle plate via the throttle cable adjustment nuts, revved it, and still got the same old stalling shit. Gotta be MAF.

[c-los13]

damn, if your ka was running good before it was turbo'ed then it has something to do w your set up
also, one of my friend did mess bolt on the TB so the TB could stay slightly open
not the wire!!!
not the best option but it works
good luck

[sleepyeyeds14]

I seem to be having the same exact problem as you. Do you ever get your car to idle for a small period of time then it jumps from ~500rpm to ~2000rpm? im completely out of ideas as to why mine is doing this. BTW im NA so you could most likely rule out any of your turbo stuff as the culprit. And please keep us posted when you find the solution to your problem! i have found many threads on this same issue, but no one ever tells us how they fix it...

[c-los13]

i had a rebuilt a ka before i got my sr
i had all kinds of idle problem before the rebuilt
my best advice is to delete all the emission and clean out maf, also itd be a good idea to clean up your iacv
check voltage on tb sensor
spray brake cleaner around the intake area and see if idle changes
thats just basic stuff

[Chugpuppy]

I seem to be having the same exact problem as you. Do you ever get your car to idle for a small period of time then it jumps from ~500rpm to ~2000rpm? im completely out of ideas as to why mine is doing this. BTW im NA so you could most likely rule out any of your turbo stuff as the culprit. And please keep us posted when you find the solution to your problem! i have found many threads on this same issue, but no one ever tells us how they fix it...

Yeah it's so annoying, all the threads I've found never have a clear answer as to how they fixed it. I'm PRETTY sure it has something to do with the MAF in my case. I'm gonna go check out the voltages.

[Chugpuppy]

i had a rebuilt a ka before i got my sr
i had all kinds of idle problem before the rebuilt
my best advice is to delete all the emission and clean out maf, also itd be a good idea to clean up your iacv
check voltage on tb sensor
spray brake cleaner around the intake area and see if idle changes
thats just basic stuff

All emissions are removed and securely blocked off, MAF has already been cleaned once, IACV has been cleaned also. Voltage on TPS is spot-on .5v closed 4.35v WOT. I have no vacuum leaks, pressure tested to 25 psi.

[LBK S13]

I had the exact same problem on my old s13 before I sold it and just as you have done I went through everything replacing all the little stuff and nothing changed. My MAF was getting good voltage and seemed to be working fine but I changed it out for a mustang MAF and it got better but still had problems when letting off the throttle. It ran fine WOT so I made it a drift slut and sold it. That said my money is on MAF just because it's getting good voltage doesn't mean it's actually sending proper signals. IMO MAF=nightmare

[sleepyeyeds14]

Yeah it's so annoying, all the threads I've found never have a clear answer as to how they fixed it. I'm PRETTY sure it has something to do with the MAF in my case. I'm gonna go check out the voltages.

What voltages are we supposed to be looking for. I want to check mine too, but i havent been able to find the specs for what the voltages are supposed to be. Also, did you ever suspect the probablem being lack of fuel pressure? Cuz i finally was abe to get my car to start today :redxd: but only for a quick second, then it died:mad: as if the fuel pump decided to stop pumping...

[LBK S13]

There is a thread with all the MAF/MAP specs. If you can't find it I'll post a link

[sleepyeyeds14]

There is a thread with all the MAF/MAP specs. If you can't find it I'll post a link

my search button wont work... so if you could post the link i would really appreciate it...

[LBK S13]

40368

I hope this helps. I still can't find the thread I was looking at earlier but I will keep searching and if not I will do some research google wide to find all I can to help because I'm sure at some point my car will have the same problem. As it has happened to my other ka in the past

[Chugpuppy]

What voltages are we supposed to be looking for. I want to check mine too, but i havent been able to find the specs for what the voltages are supposed to be. Also, did you ever suspect the probablem being lack of fuel pressure? Cuz i finally was abe to get my car to start today :redxd: but only for a quick second, then it died:mad: as if the fuel pump decided to stop pumping...


My fuel pressure is fine, the car's dying out because it's bogging RICH, not lean like most vacuum/fuel pressure related problems.

I'm pretty sure I just need to extend the MAF away from the turbo or go blow-through, I've been talking to Martin at RS Enthalpy and gotten some good information. These things are apparently very sensitive, so he recommends placing the maf 18 to 24 inches away from the turbo. I'm gonna rig something up for now, and if it works then I'm cutting a hole in my inner fender, boxing it to protect from dirt/dust, and stuffing the maf/filter down there. Top-mount sucks for space.

[waxball88]

I have been fighting with the same issue for a while. I'm hoping its just vacuum leaks. After i put my manifold on today i will know 100%
Things i've tried
Replaced wastegate(was leaking)
Different throttle bodies/TPS
Injector seals/cushion rings
Different n62 mafs
Boost leak testing
Timing check
Fuel pressure regulator/filter
Cleaning IACV
Moving maf away from turbo with 90* bend
Converting pre-tb to IACV tube stuff to push lok AN (never leak again)
Tried isis egr block but it leaked, so i just had the hole welded shut.

Manifold going back on today. It will be the most optimum set up to prevent any sort of leak.

[jmac636]

Before going blow thru just try extending the distance from the turbo to the maf. Do it as a temporary experiment first. Your maf is most likely too close to the turbo creating a turbulence of some sort that your maf doesn't like. Z32 mafs are far more sensitive to this. If you go blow through with the z32 maf you will blow off the sensor cover if you don't reseal it with epoxy. Blow through will make the car feel like it was turboed from the factory. No stalling or ill effects. Make sure you don't have any reducer in front of the z32 maf.

[Chugpuppy]

Before going blow thru just try extending the distance from the turbo to the maf. Do it as a temporary experiment first. Your maf is most likely too close to the turbo creating a turbulence of some sort that your maf doesn't like. Z32 mafs are far more sensitive to this. If you go blow through with the z32 maf you will blow off the sensor cover if you don't reseal it with epoxy. Blow through will make the car feel like it was turboed from the factory. No stalling or ill effects. Make sure you don't have any reducer in front of the z32 maf.

Are you running blow-thru? I'm gonna move the MAF farther away using a temp setup tomorrow, but I'm not quite sure how I could go draw through if it did work. What's your setup look like?

[lysticalz]

any updates chug?

my cars been doing the same thing after i switched from safc2 to an enthalpy tune and z32 maf a long while back.

[Chugpuppy]

any updates chug?

my cars been doing the same thing after i switched from safc2 to an enthalpy tune and z32 maf a long while back.

I put at least 2" of pipe between the MAF and my 20g, and that helped a LOT. Way better response, drivability, and AFRs all around. It was running PRISTINE for about half an hour, then I shut it off and tried hooking up the idle air control systems and resetting the throttle cable. Now it runs rich EVERYWHERE. :cry: Screwing around with it some more when I get home from work today.