New issue. smooth in boost at first, then later on sputtery/misfires...;

[zerepdivad]

Ok you might have seen my last thread where i was having some boost leak issues and such. WEll now i got all of that taken car of * i think so at least *

I'm smooth in boost once again and it pulls as it should and once i removed the egr, and fixed a lot of vacuum leaks and got rid of unneeded lines i went from 9 psi to 11. So that was kind of a plus i suppose.

Here's the issue though. Upon start up in the mornings the car is smooth and is smooth in boost. But after driving for about 20 minutes or so if i get on it it gets real sputtery/ misfires. I'm thinking it may be an issue with possibly my coil? It maybe is getting too hot after driving for a while.

Because when i boost leak test after driving it for a while it holds pressure up to like 20 psi so i know it's not a leak in my piping. And it's just plain odd that its fine upon start up but once it's been running a while it breaks up under boost. That make any sense to anyone out there? Or have you possibly had a similar issue? This one kind of confuses me a bit honestly. any help or suggestions is appreciated.

[Infinitiguy19]

Check the knock sensors, injectors and the coils.

[zerepdivad]

Injectors should be fine i don't foul plugs and i don't go insanely lean ever so i'm sure those are good. No leaks on them either. Unsure as to how to test the knock sensor...., The ignition coil is what i think may have something to do with the issue.

I've been daily driving the car the last week and it's the same thing everyday. Plenty of power and is smooth in boost when i first start up and go somewhere. But once i'm driving for like 15 minutes and get on it it makes like a weird popcorny sound? and somewhat misfires only during boost though. Regular driving is normal.

[TJcars2]

What are your spark plugs gapped to? You could have spark blow out.

[zerepdivad]

.030 is what they're gapped at. I doubt it's that since it's good on initial starts but it sputters and whatnot during boost once i've been driving a while.

[Lonismos14]

sounds like detonation

[zerepdivad]

I doubt it's detonation. It's done it many times i cant imagine a stock ka holding up to detonation that many times. And why would it only do that after i've been driving a while?

[neverlift]

sounds like det to me as well from the description

heat soaked pistons are more prone to det.

I have looked over at my wideband and seen 20:1 at 11psi , as far as I know my motor is stock stock, but it does have 212psi compression across. Making it a freak in general

[zerepdivad]

Yeah but my afrs while it's missing like that are like low 12s high 11s on my aem wideband. I thought for detonation it was supposed to be really lean?

[trackslut240]

have u checked ur coil? coz i had a similar issue when i was non turbo, after a while of driving, it would be missing, i can see some black smoke on hard accel. how i figured it to be the coil is, i put a piece of insulation from the car floor on it and poured water over it. for a little while no probs, then once the coil heated up, same issue. swapped the coil for another one and then no problems. try that and see.

u r rich like that when it sputters in boost or even out of boost?a cracked ring land runs funny, it does get sputterry on higher revs, at least from what i learned when it was non turbo. i had a cracked ring land on #4 piston, if i get on it, sputter. it would take forever to gain speed and would sputter all the way. i cant remember if it did that when cold.

do a quick compression test, it will rule out cracked pistons or ring lands.

good luck man...

[zerepdivad]

can any body help? should i get lowering frist or coil?

EH?

I don't get smoke or anything of that nature under boost. Those are fairly normal afrs even when it doesn't sputter so i know i';m not insanely rich or anything. The thing that's got me weirded out is that it pulls great with no sputtering or missing when somewhat cold but when warmed up after driving for a while i'm like missing really bad. Don't understand it at all.

[WDRacing]

Knock is caused by ALL kinds of things. What's your water temp when it starts to knock? I really really easy way to see if it's detonation is to mark the dizzy where it's at right now, then retard it a few degree's no more then 5. Basically just a small bump backwards, whats that counter clockwise right? Then test it again, see if it has the same or different symptoms. Then realign the timing marks and retest, noting all changes.

Check your wires, I had a similar problem a few years back, turns out my #4 wire wore through and was grounding out. I didn't notice it until I was really into boost. Not the same issue, but it's definitely worth a look. Might as well pull the plugs and have a look to. If any of the plugs look different, snap a pic and post it.

WD

[RunninMeBrokeS13]

what is your base timing set at? what tune are you running? what a/f reading are you getting when this happens?

[WDRacing]

what is your base timing set at? what tune are you running? what a/f reading are you getting when this happens?

Dude...

Yeah but my afrs while it's missing like that are like low 12s high 11s on my aem wideband. I thought for detonation it was supposed to be really lean?

i went from 9 psi to 11.

I told him to check his timing already and even try retarding it and testing to see if the symptoms remain or change. If you can't keep up take notes

[zerepdivad]

I did go ahead and retard the timing a bit and it seemed to be about the same. It's hard to describe. It still "pulls" but it feels like it loses power for a sec, then gains it then loses then gains it, once warmed up. And sometimes i hear like a "popcorn popping sound" if that makes sense. I'm gonna mess with it some when i get off work today.

[WDRacing]

Popcorn means knock. I've blown 4 or 5 motors pushing the knock envelope and every time I heard it it was almost to late. To me it sounded like having my ear right over a bowl of rice crispies and milk...lol.

Things to check:

Base timing.Plugs for discoloration.Fuel pressure, static and on boost.Compression.

One thing to remember, the ecu pulls a ton of timing when the knock sensor registers any noise. As the motor warms up, knock can occur easier. The motor also leans out once warmed up, not lean meaning you're dangerously lean, but it's always richer on start up. So as the motor warms up it makes everything is hotter, from the fuel entering the motor to the block itself AND the mix is leaner then it was when cold.

I'd run a can of seafoam though the intake to clean any deposits etc. Maybe fill up with some good gas and add some water remover and octane booster in case you got a batch of crappy gas. Do those things after you check the above, if you can't check fuel pressure it's not a biggie since you have the wide band. But plugs/wires/compression/base timing should all be checked and then do the seafoam and fuel additives. Might wanna change your oil after the seafoam as well, can't hurt to have a fresh place to start.

WD

[zerepdivad]

Ok well i found my timing light and my timing is at 20*btc which is stock. My plugs look ok my fuel pressure was at 35 and i bumped it up to 40 and took it for a spin and it still did it. I've still got to do a compression test which i've got to exchange my pos autozone one. I took a video just now and am in the process of uploading it as i type this. Not sure if you can quite hear but i definitely got it on tape, so hopefully you can hear it.... I'll upload in a bit. I'm starting to think maybe i got a dying cylinder or something. hopefully not but we'll see i suppose.

[zerepdivad]

http://www.youtube.com/watch?v=ZfkI2qE8N7o

On the first pull you can't really hear it because it barely did it but on the second pull you can hear what i'm talking about. Any ideas?

[Razi]

Sounds like detonation, but perhaps it could be a loose exhaust bolt or something that is rattling?

I get a very quiet rattle when transitioning into boost.Now you guys got me worrying.
Modified by Razi at 2:28 PM 12/4/2009

[neverlift]

if you guys think you have some detonation you should get a timing light and pull a couple off, then do some testing.

[D-UNIT]

I can see your fuel level is close to empty. Do you always run it low like that? Running less than 1/4 tank all the time can burn up your fuel pump. My car is doing something like that right now. I'm thinking I have a hole in the intank fuel line or my 5 year walbro is about to die. It had a good run.

[D-UNIT]

nope not my fuel system. fuel pressure was higher than normal so I changed the fpr to spare one I had and same problem. I think it is my coolant temp harness wires cuz when I touch the engine harness my idle rpm goes up to 2000. gonna check with a scan tool tommorrow.

[zerepdivad]

I don't generally go that low on gas. I actually filled up after that video and it did the same thing. I actually haven't touched the car since that day because now there's snow on the ground here. So it'll be a few months. I bought a compression tester the other day though so hopefully that will help narrow down if i got a low compression cylinder possibly?

[D-UNIT]

good luck my engine is brand new so I know my compression is good. Tried to tow it in gear and the the tires dragged on the ground. I having the same problem as you. I'm leaning towards fuel pump. gonna pull it out tommorrow and test it. This is what I did so far.....

Changed--

FPRcap and rotorignition coiligniton coil wireyanked a set of stock ign wires off an altimasparkplugscoolant temp sensorknock sensor off altimaengine control fusecut open harness looking for bad connections

NOTHING HELPED!!!!

but I did changed the fuel filter yesterday and it seemed to run a little better for a longer while , but then started to act up again. Arrrgh!! gotta be fuel pump or in tank connections. I WANNA BOOOOSSSTTT!!!!!

[biggie]

Didn't read everything, but...

Mine was doing this on my first real test drive. Smooth until I hit close to 6k RPMs. Noticed by FPR had moved a little and the FP was too high, apparently dumping too much fuel.

Do you have a FP inline gauge to see what your FP is at?

[D-UNIT]

Sorry to thread jack but I need help too. what did you do to bring it down? I tested FP the first time and I had 41psi at idle and 52 no vacuum. So I change the fpr and same problem. So I check FP today before yanking Fpump and wadaya know 51psi and 62psi on boost. WTH is going on. I thought it was leaning out but I guess(hope) it wasn't.

[zerepdivad]

My fuel pressure is at around 35-40. I have a nismo adjustable fuel pressure regulator.

[D-UNIT]

FSM says FP should be 35(vac) and 43psi no vacuum/ boost. You could be leaning out slightly up top. How did you make the nismo reg fit? did you get that special reclocker from xcessive?

[D-UNIT]

I watched your vid again and I'm think plug wires or cap and rotor. could be anything

[biggie]

FSM says FP should be 35(vac) and 43psi no vacuum/ boost. You could be leaning out slightly up top. How did you make the nismo reg fit? did you get that special reclocker from xcessive?

I have a Nismo FPR as well, stock rail, greddy swivel adapter from enjukuracing, and inline FP gauge under the hood. I'm set at 35/43 (vac/no vac). When I was having the problem it was around 43/50.