st280

So I've searched and searched and searched.

Set up:
FP 20g w/hks actuator 16 lbs
540 cc Sti injectors
Z32 MAF
Nistuned with this setup
Basic bolt ons:
headers
3" exhaust
fmic
255 lph walbro

Ok, it just started doing this 2 days ago. And it had been pouring rain here in the Valley for the past 2 weeks. (Don't know if that could be related or not). Anyways, was leaving work, kinda punched it going around a corner, everything fine. Come up to the light, and car seems to have a slight stutter to it every couple of seconds, idle will drop, vacuum will drop. I start to take off seems like it's missing more, as if firing on 3 cylinders. So I just cruise it home, everything runs fine while cruising, just taking off and more than half throttle is when it breaks up.

I get home, start jiggling wires around to make sure none of the injector wires came loose, or nothing was loose. Nothing changed, still had slight stutter every couple of seconds. I changed spark plugs today, and it somewhat cleared up the stutter at idle, but whenever I hit boost 2 lbs or above, it will just stutter, buck, and misfire. So I can't boost at all.

Thing's I've checked/ruled out:
-I haven't touched the car engine bay wise in about 2 weeks. (So can't exactly rule out most recent thing I've done)
-Has new Walbro fuel pump.
-New z32 fuel filter.
-Has had the Z32 MAF for over a month.
-No boost leak, unless something came ajar in a second? It holds vacuum at 19/20 lbs ok. And I have boost leak tested it.
-Checked injectors, unplugged each one at a time, each causes it to shake violently.
-Adjusted TPS/tried new TPS
-AFR's via wideband all seem to be just about normal, don't see any major fluctuations, even when bucking occurs.

Only thing I can think went wrong was the turbo? But there is no smoke, and I can hear it spooling while I'm driving. I will be taking off the intake to inspect the turbo propeller blades on Sunday.

Any other things I should check for? I hate not being able to figure this out on my own...

Thanks

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Tantwoforty

things i have had happen to make this happen
1. bad fuel pump/filter.. low or inconsistant fuel pressure.
2. collant temp sensor, idk why it caused this.
3. CAS went bad.
4. bad coil on a clynder.
5. boost leak
6. seized turbo, dude who installed it used teflon on feed line, bad.
7. bad seized or stuck actuator.
8. bad or stuck injector
i know you checked some of these but idk.
hope you get it figured out, those reasons are pretty much all the big ones i came across from working at a shop for 2 years building turbo cars..
best of luck

Waylayer

A big tell on what the problem is would be what you AFRs are doing during that time.

Edit: Just read that AFRs didnt do anything out of the ordinary.

I'm going to keep thinking about this, but when my car did this, it was because it was running really lean do to a failing Fuel pressure regulator.

Check your timing also, and how much gas in the tank did you have? Could also be bad gas freaking out the tune.

fliprayzin240sx

Have you checked the spark quality? Take the spark plugs out, double check to make sure they're gapped down to .030-.028, stick it into the coilpack, ground the sparkplug to the head and crank the car. Check and see you're getting good spark.

Also, double check the ground wires for the coilpacks. Personally, i've grounded mine straight to the firewall.

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st280

I was able to move the actuator arm (tough) but it moved.
And all of the items on this list would keep me from boosting at all?

I was thinking bad gas also, I had just filled up at a Chevron that I frequently get my gas from. I also put in some Iso-Heet in case the gas was bad/had water in it from the floods around here.

My car just recently came from DC Performance, and they said timing was ok.

I'll swap out FPR on Sunday, with a nismo regulator to see if any change.

I'll check spark on Sunday. One thing that concerns me though, would something like this just happen out of the blue as far as if one of the coil packs went bad? And if say a coil pack went bad, would it cause me from seeing any kind of boost?


Thanks for the replies guys.

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encludemeout

What kind of intake are you running? Sounds like you are hydrolocked, sir. If so, just don't get into boost, and give it a couple of days to dry out. It'll be fine

Used to happen to me anytime it would rain and I would get into boost. Water gets sucked up, and bam, no boost for two days.

st280

Hydrolocked? Where at? I have an HKS intake.

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st280

Been brainstorming... Would a faulty actuator/wastegate cause the bucking? I'm thinking if it's not sealing up properly, then it's not letting boost build up, and making it run too rich to cause the bucking?

I was thinking this because it seemed as though when I try to boost/when it starts to really buck the AFR seems to be 11.0 or lower.

Thoughts? Hopefully this stupid Cali rain stops tomorrow.

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hektik13

had same problem i had a faulty actuator replaced it, it helped but still did...then gapped the spark plugs to .28 ran fine

st280

Regapped the spark plugs to .28. And swapped out the actuator. Still having same problems. It is actually making it up to around 5 lbs, but it is really shaky making it up to that now... I also checked the intake side turbine wheel, everything is still nice and tight. Normal shaftplay, no chips or anything... Video is being uploaded right now to show what is going on...

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st280

YouTube - sr20det boost problem...

YouTube - stupid sr20det

Hard to tell, but it's shaking and ish once I get past 0 lbs.

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KaminaSan

Had this SAMEEEEEE exact problem dude. last time we had rain in cali.

BAD COILPACK and plugs.

I would rev just fine free revving. It would drive fine with no boost(slow accel), but as soon as I hit boost in the 3500 rpm range, it would buck and or not build boost properly.

Took it to my garage, and they pulled the plugs, which were all jacked up, and one coilpack was completely miscolored and white.

Threw in new plugs and coilpack, and it ran SMOOOOOOTH.

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st280

a LITTLE update.....

It's fixed. It WAS bad coil packs. 3 of them were cracked up, but I never had a problem with them until the stupid rains that we had...

Borrowed 4 non-cracked good working ones, threw them in. And everything is good, no break ups, can boost up fine, etc.

Thanks for the help guys!

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