Jake_240sx

Hey all,

Long time follower on here, and a few other forums. Most of the time I've been able to search and find the answers to my problems, but this time I've come up empty handed. I am at a loss, and need some help.

Here we go:
S13 Chassis, SR20DET
Stock: Engine internals, turbo, FPR, MAF.
Walbro 255 fuel pump.
Aftermarket FMIC.

Car had the swap done last year. Has run fine up until yesterday afternoon.
She's been running about 9 lbs of boost without any issues (never lean).
A good friend of mine(bought the car from him) and I decided to put the boost controller that was in the car back into it. I had seen the car run 15lbs (for a few months) without breaking a sweat. First pass, only made 5 lbs. Adjustment made. Second pass, made the normal 9lbs. Adjustment. Third pass, boost went past 15lbs up to 20lbs. Immediately came off the throttle, pulled over for another adjustment. Fourth pass, made 15lbs, right on the money. Then she starts getting squirrely. As i decelerate, she starts bogging, starts bucking, and feels like she's only running on 3 cylinders. I immediately think I've just put a rod through a piston face (scariest environment imaginable). First thing we did was pull the controller, and put the vacuum lines back to the way they were. No change. We get the car back to my house, and we start diagnosing.
From the top:
Fuel pressure reads 42 psi at idle. It goes to 50 psi when vacuum line is pulled from the FPR. Fuel pressure is also affected correctly by the addition of vacuum(from hand-held pump).
No fuel in the vacuum line for the FPR.
Spark plugs are all gapped properly. None of the plugs were wet when I pulled and checked them.
Conducted a compression check, all the same, all normal.
Car has a full tank of good fuel.
Injectors resistance was the same across the rail, and within parameters.
Conducted a boost leak check, found a few small ones, and fixed them.
It sounds like there is still a small leak coming from the turbo(unconfirmed, need to get it up on jack stands to be sure).
Wastegate actuator works as it should during boost leak check.
Disconnected the MAF, car stalls when I try to drive it. Doesn't stall when its connected.
I individually disconnected each coil pack and each injector. With each disconnect, the engine idle got worse.
The only thing that was changed was the manual boost controller. It was removed, and the effects have stayed with the car.
I need some help guys. I'm pulling my hair out going through what it could be. I'm hoping someone out there knows exactly what I'm talking about. I am open to suggestions and questions. And before I get flamed too hard, I spent the last hour searching zilvia and 240sxforums for an answer. Nothing matches the symptoms I'm experiencing.
Thanks in advance,
Jake

cotbu

Aside from the fuel pressure being high, and the tune being slightly off for it. I'll elaborate
370's at 50psi base flow about 396cc min\37.7lbs hr instead of the correct 370cc min\35.2lbs hr. You could be just over fueling, which could cause your symptoms.
Pull codes, if no codes are stored. verify timing, if base timing is correct, try adjusting the fuel pressure to: vacuum disconnected 43.5psi and with vacuum connect and pulling 20inhg/9.8psi subtract from 43.5psi would roughly be 33.7psi with vacuum connected.

This may not solve your problem, just what I gathered from your description. G\L

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ultimateirving

Did you try to pull codes from the ECU, Whats ur ECU say?

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Jake_240sx

I unbolted the ecu, tried to get it into diagnostic mode, wouldn't do it.
Id like to verify that what I did was correct:
Unbolt ecu.
Locate screw and led window.
Turn key to acc. Ecu should blink (mine does not).
Turn screw fully clockwise, wait 2 seconds, turn screw counterclockwise.
Wait for flashes(mine does not).

Car ran fine, a little bit rich at times, before the increased boost.
At this point I'm trying to diagnose anything that could have been affected by the increased boost levels. Iacv works like it should. Tps works just like it should.
Could I be looking at timing issues?
I'm about to check the coolant temp sensor.
I'm going to try and get my hands on a known good injector and swap it out one by one, and see if one of mine has been buggered somehow.
With the encreased fuel pressure at idle and load I'm not thinking its the pump or the filter. Which only leaves the fuel rail and the injectors.
I'm going back to basics now: air, fuel, spark.
Air is good from everything I've checked so far.
Fuel is good up to at least the rail.
Spark plugs keep coming out dry(no extra fuel in the chamber from lack of spark).
Also severe negative changes when each coil pack is disconnected.

Still open to any and all input/suggestions.
Thanks again guys.
Jake

Jake_240sx

UPDATE:
Made the realization that the issues I'm experiencing is only AFTER the engine warm-up period, my understanding 45-60 seconds. Once the ECM starts to listen to sensor inputs, she bogs, has no power, and feels like she doesn't have compression when you try and accelerate.
I noticed that if I drive it and watch my boost gauge, keeping it under 10 inHg, she acts totally normal.
I am suspicious now more than ever of the boost leak i noticed coming from below the turbo. First thing tomorrow morning I'll get her up on jack stands, and re-pressurize the system and hunt the leak down.
If that still doesn't solve the issue, I'm taking her down to a local shop that has diagnostic equipment, and one of my friends works there.
Also, coolant temp sensor resistance is normal when cold.
I'm hoping that hooking up to a consult cable and computer will tell me exactly what I need to know. Guess we'll see. When/if I find the answer I'll be sure to post it.

Jake

cotbu

No incorrect, fixed it for you. G/L 5000!

I just wanna say, the more I think about it my comment seems more and more likely. As I keep picturing your responses.
As soon as you warm up or reach operating temp, closed loop the ecu take over. When it does it can not every inject the correct amount of fuel. Anyway G\L Versace outfit cost me 3000!

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Jake_240sx

ECU Codes pulled:
12, 34
Are those the "diagnostic Procedures" listed in the FSM?
or are these codes listed somewhere else?

ultimateirving

code 12 - bad maf/bad connection
Code 34- Bad knock sensor ( this easy to test and replace)

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Jake_240sx

I agree with 12, MAFS.
My FSM says 34 is Knock Sensor.
Thoughts?
Jake

ultimateirving

oops my bad, looked at wrong code, ur right 34 is knock.
This can be checked pretty easy too, but you need a multi meter

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Jake_240sx

UPDATE:
Conducted another boost leak check, found a few pin hole leaks in silicone boot seals, sealed them up, and now no leaks(tested to 15psi).
Chased out the Knock Sensor code. Can't seem to find anything wrong.
When disconnected she runs no differently.
Chased out the MAFS code. Again, can't seem to find anything wrong.

I have noticed that during idle when she stumbles(feels like a misfire) that the A/F ratio leans out temporarily. I am hoping to borrow a know good fuel rail, FPR, and injectors from a friend and see if that's the issue.
Might not be able to get my hands on that until the day after tomorrow.
I'm open to other suggestions in the mean time, I've got a day to kill anyway.
Jake

ultimateirving

U should spend a few bucks and buy a multi meter, You can test so many things with it! so many activities with a multi meter.
Honestly tho, if u get one Id start testing voltage and continuity on the MAFS,TPS, and CTS.

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Jake_240sx

Have a multi meter. I've been checking against fsm values. Resistance and voltage, etc.

Jake_240sx

UPDATE:
Here's what I did today:
Clear codes.
Drive it.
-Codes came back, same.
Watch stoich levels during limited boost rise.
-Was a little rich, not 10, more of a 12.5.
Check MAF voltages when running.
-All normal.
Check coolant temp sensor warm resistance.
-Normal per FSM.
Listen to idle, pull injectors one by one. Listen for misfire, NOT just a drop in rpms.
-Drop in RPM occurs with every injector and coil pack disconnected. Cylinder 4 was the only one that, when removed from the drive train, did not stumble. When the suspect cylinder was still in the drive train, it would stumble down to 2 cylinders. This leads me to believe that my issue is either spark or fuel in cylinder 4.
Pulled coil pack 4 and spark plug 4. Swapped with coil pack and spark plug from cylinder 2.
Check coil pack resistance.
-All normal per FSM measurements.
Rough idle is way less noticeable, and the stumbles were further between. So much so that when i removed cylinders 2 and 4 from the drive train, could not notice the stumble. Read a little bit about similar issues. Discovered the ability for the coil pack to become weak(sometimes spark on a big gap, weak spark with boost, or no spark with high boost), and not completely fail(no spark at all). I remembered re-gapping the plugs during the first day as part of my troubleshooting (.036, as per the FSM). Apparently when I introduced more boost, at a fairly "normal-large" gap, the coil pack couldn't create the spark, and fried itself. Not noticeable with FSM checks of resistance, or continuity with grounds.
MAYBE that gap was a bit much, considering some guys run a .028 with boost levels in the 12-15 psi range.
Plugs regapped.
IT CREATES BOOST!!!
ok, only the normal 7-9 lbs, and it still breaks up a little above 5 psi..
Replace fuel filter
-Needed it, and wanted to check it off my list.
Replaced spark plugs.
-Again, needed, and wanted to check it off my list.

Should be getting 2 known good coil packs tomorrow. Will swap it out with my suspect one, and then I will repost and update.
I'm seriously hoping it's just a bad coil pack. I've also got a known good fuel rail and injectors that I might swap in if the coil pack doesn't fix it.

Thanks for all of the input guys, I appreciate all your help.
Jake

KendallH

Check your fuel pump and gas tank. I've seen a lot of S13s (including my own) have crud and rust buildup in the gas tank and it clogs the fuel pump.

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Jake_240sx

Thanks for the advice. I was gonna check it out tomorrow. Hoping I don't need to clean out the tank. Would you advise a simple visual inspection at the pump mount location?
Thanks.
Jake

KendallH

Pull the whole fuel pump assembly out and either use a gloved hand or some kind of scoop to check the bottom of the tank. Its not always easy to see, when I was having issues with my SR I replaced and cleaned the pump twice before noticing all the gunk in the tank.

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Jake_240sx

Good to know. I'll check that out tomorrow when I'm swapping the coil pack. I'll post what I find down there..
Jake

Jake_240sx

CONCLUSION/PROBLEM SOLVED:
Bought a new coil pack from a friend, swapped it with my suspect coil pack.
She runs perfect. Holds boost all the way up to and at 9lbs. No sputtering/misfires at all.
I hope this thread helps somebody down the road. All the ones I found about similar issues never had an end or a fix.
Thanks for all the help guys.
Jake


Now.. what to do with this old coil pack...?
Maybe a neat e-brake handle..

ultimateirving

Nice man glad to hear!

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Twiglet240

Man I have the exact same problem thanks for posting. Ill check mine next.