Silvia Running Lean - 13.1 @ WOT no power

[veloz]

Hey Guys,I usually search and don't post.

I Tried searching but have not found anyone so far with my problem.

I have a 94 Silvia

Has anybody had a simliar scenario?My only guesses now are clogged/dirty injectors or failing FPR.

My car was running great. Very quick and ARF's at WOT 11.5 - 11.8 in 3rd

All of a sudden, the car began to run lean. AFR's were 13.2, 13.1 at WOT.Sometimes they dip to 12.5, 12.6

The car also bucks, studders and hesitates. It feels like it has no power compared to before.

I added 10% more fuel accross the board just to test.(3K - 8K)Hesitation gets worse, AFR's stay the same.

Mods:Walbro 190300zx fuel filterS14 SR20DetStock S14 SR Maf94 octaneGt2871RS Turbo @ 15psiFMIC and PipingNismo 555 cc injectorsNISTUNE Standalone

I figured it could be my maf.I swapped out and cleaned it, no diffrenceI swapped a known good one in my car, no diffrenceI swapped mine into a good car, no diffrence.

maf = good

I thought it was the fuel pumpPulled the pump and put in a brand walbro 255No diffrence.Pump = good

Any Ideas?

Thanks


Modified by veloz at 8:40 AM 10/8/2009

[Emperor_Tha]

Clog injector, clog fuel filter.

Possibly a vacuum leak.

[mRodiek]

Vacuum leak, check FPR pressure, how much boost are you pushing at WOT? Could be leaning you out if your injectors cant match it

PS-your car is a 240sx, not a Silvia

[veloz]

Vacuum leak, check FPR pressure, how much boost are you pushing at WOT? Could be leaning you out if your injectors cant match it

PS-your car is a 240sx, not a Silvia

My car is a Silvia.RHD S14 from Tokyo.



Would a vaccum/boost leak cause it to go LEAN at WOT?

Fueling was always good before this scenario.

I'll check FP as soon as possible.

[pauliedrft]

go to lowes or a hard ware store buy a t and a fitting that will make the top go to a 1/8npt then buy a fuel gauge and put it in line from fuel filter , you can keep an eye on your fuel pressure for like under 20.00 dollars . then you already have your gague for a after market fpr .Do a boost leak test if you have a vacuum leak you might find it that way .

[Emperor_Tha]

Vacuum leak = boost creep and over boost

can cause a lean issue.

[WizardBlack]

A vac leak can potentially destroy your engine. The FPR runs a vac reference. If you lose the pressure to the fpr you will get the fuel you need at 0 psi when you are boosting max. Be careful boosting in your condition. A vac leak in another area won't do this.As devil's advocate, increasing fuel should make it run richer; even with a vac leak. Increasing fuel should make it run richer with a clogged injector. Not necessarily so with a bad fuel filter.Check your plugs for imbalance that indicates a clogged injector.Check your fuel pressure for a failure in the pump/lines/filter.Visually inspect your vac lines very carefully. Tug and wiggle on them.

I tell you, though, bucking and stuttering sounds like a fuel ratio imbalance between cylinders. If one has dropped out somehow, the averaged air fuel ratio will be much leaner but not dead lean. Bucking and stuttering could be a the other cylinders choking on extra fuel (spark blowout).

Plugs are probably the biggest indicator of where to look next. That, and compression test.

[veloz]

A vac leak can potentially destroy your engine. The FPR runs a vac reference. If you lose the pressure to the fpr you will get the fuel you need at 0 psi when you are boosting max. Be careful boosting in your condition. A vac leak in another area won't do this.As devil's advocate, increasing fuel should make it run richer; even with a vac leak. Increasing fuel should make it run richer with a clogged injector. Not necessarily so with a bad fuel filter.Check your plugs for imbalance that indicates a clogged injector.Check your fuel pressure for a failure in the pump/lines/filter.Visually inspect your vac lines very carefully. Tug and wiggle on them.

I tell you, though, bucking and stuttering sounds like a fuel ratio imbalance between cylinders. If one has dropped out somehow, the averaged air fuel ratio will be much leaner but not dead lean. Bucking and stuttering could be a the other cylinders choking on extra fuel (spark blowout).

Plugs are probably the biggest indicator of where to look next. That, and compression test.

Thanks for your post.Very informative.

I went straight the the FPR Vaccum line and checked that it was still connected.That line is fine.

I'll have to wait till tomorrow to check compression, plugs, coils, etc.I'm also testing FPR and pressure.

I like the theory of the fuel imbalence and I'll try to get some proof this weekend.

I probably will try to run a boost leak test as well.

[veloz]

Alright,

First of all, I think I would have blown my car up IF I DIDN'T HAVE A WIDEBAND,Trust me, you'll thank yourself later!

Got some time today and tested a bunch of stuff

FYI - My timing is perfect.

1) I checked my Fuel pressure and regulator.

Line off it tested at 50 psi. Line on it dropped like normal.

2) I checked and changed my plugs back to copper bkr7e's instead of the bkr7IX I was running.

The plugs looked normal. No clear signs of imbalance.

Still studders and runs lean = No difference

3) I checked over my coil pack wiring and it "looks" good.I'll have to check it more thoroughly later, in any case, i have a spare harness.

4) I checked my coil packs and tried a known GOOD set = No difference

5) I checked to see if adding fuel would help... It studders worse.

The "best" AFR I can see is 12.6 and it scares me to hell being that lean.

6) I checked my normal fuel delivery at idle by disconnecting the o2 sensor

It runs about 14 AFR at idle w/o o2 as compared to 14.7 - 14.9 with the sensor connected. It's not bang on, but it's close.

Car still runs like poo.



Recap - I've checked my: o2 sensorMafPlugsFuel pumpFPRPlugsCoilsWiring Turbo

So, now I'm here scratching my head even more.

Only obvious things to left to check are Compression, Injectors and Boost leaks as WizardBlack said.

Compression and boost leaks seem good but I will check them regardless later.

Injectors are a pain to do on and S14 SR as I have to disassemble the intake manifold

BUT..........................



THE other thing I was thinking about is the possibility of a clogged CATALYTIC CONVERTER.

It runs fine with low back pressure but as soon as I boost, it chokes. This would cause the AFR's to show lean, cause a loss of power and probably the studdering as well.

Luckily, I'm a parts whore. I have a straight pipe to install when I get a chance.

Besides that, I'm fresh out of ideas.

Any thoughts or theories?

I wanna spend more time drifting and less time fixing!


Modified by veloz at 10:24 PM 10/13/2009

[veloz]

Put the straight pipe in.

NO diffrence.....

I'll have to start testing injectors, boost and compression when I have the space.

[veloz]

Any other Ideas guys?

I'm not sure what else to swap that doesn't cost a bundle...

[NISMOlvr]

check your intercooler piping especially intercooler,A buddy had same prob ,no wide band and blew his motor cause intercooler had a pencil size hole in it.check all vacuum hoses.fuelpressure @ idle should be 36psi ,off idle should rise to 41psi.
Modified by NISMOlvr at 11:18 PM 11/9/2009

[homeslicej2]

You state you have NISTUNE so, have you checked to make sure it's not in the tuning?

[veloz]

I have run a compression test. 150psi COLD across the board.

I've also tried putting the tune back to stock S14 Sr20det Map.

No change.

I still have to run a boost leak test.

[NISMOlvr]

ok this might help. I dont mean to jack this thread. I will speak from personal experience. I have a blacktop from rps13 with t28,z32 maf ,480cc injectors and emance tune.wallbro 255 nismo fpr ,FMIC.I increased boost yesterday to 12psi.I have a plx wideband and its hooked up to my ecu.I noticed from time to time my car would beging to run lean when i began to boost ,afrs would be 13 and so on.felt like it had no power.so i checked fuel pressure at idle it was 36psi and 41psi off idle.so I checked for vacuum leaks and could not find any.I would start car next day or a short time later and lean condition would go away ,i mean this thing ran great ,no more leaning afr at wide open was 12 and lower.I checked battery voltage and ground straps on engine bay.Finally i decided to check voltage at fuel pump,it was low 12v.I went to auto part purchased 12 gauge wire bosch relay and connectors and a switch,I just finished wiring it up with switch on ground side of relay ,damn this thing starts right up now and voltage now at pump is 14+.also switch will completely disable pump ,added piece of mind.also no more pump whinning noise.

one of the most over looked things to check is fuel pump voltage.check yours .hope this helps

Modified by NISMOlvr at 6:15 PM 11/12/2009
Modified by NISMOlvr at 11:06 PM 11/12/2009

[Sil80315]

Check voltage to Maf and fuel pump. Also Im not to familiar with NISTUNE but if nistune runs on open loop tune off the wideband o2 sensor then it could be a bad o2 sensor (unless you swapped it out. I noticed you said you checked it)

Another thing you can try is to take out the Injectors and see if they are blacked and try sending them out to get sonic cleaned

[240zac]

try turning the boost down and see if it runs better.... maybe you are maxing out the MAF?

[Didderson]

My first thought is you haven't checked for leaks in your IC piping system yet right? I saw you did a compression test but you could have a leak in the IC or piping somehow. Maybe a coupler has a cut in it now or a rock busted a runner in the IC. The fuel pump voltage is a great suggestion also.

[veloz]

Hey Guys,

Getting ready to come out of the year.

Did some work last weekend and removed my manifold.

Manifold was cracked at the collector.

I think that my have been the main problem.

Will keep you updated.

Thanks

[veloz]

So, it continues.Crack was the MAJOR problem, as I could easily fit a paper clip inside it. It was about 2- 3 inches long all around.

I checked boost leaks and I have a small, small leak in between my T-bolt clamp and my piping.Worm clamp should fix that.

To my surprise, all the lines are okay BUT I'm leaking like crazy from where the BOV is supposed to be sealed (piston itself, BLITZ BOV) AND from my Intake Manifold to Head gasket.

It holds only about 10 psi, and tapers off. Definitely going to be running on low boost for a while.

I pulled off my Tubular Manifold (I had to remove my Cas) and now I have to reset my timing and probably switch valve covers while I'm at it and go for a test drive.

If I'm lucky, it should be out next week for a test run, and go from there.

You guys that suggested a boost test were right.

Only reason I was running okay, was because I was compensating with my stand alone.

[veloz]

As you can tell, I don't have a lot of time any more to work on my car.

Took it out for a test drive, and it is still running a little lean.

I will be installing my Intake manifold spacer, which SHOULD get rid of my major leak, and find a new IC clamp.

The Good news is that it DOES feel like it has power back, but it is still running a bit lean.

I think that may change once I fix the boost leaks and redo the tune.

[MR.chris]

Keep us posted. I am having very similar problems.

[veloz]

Okay, So I found I had another exhaust leak .One of my turbo elbow studs broke so I replaced it with the newest style MEGAN Elbow.I now have ZERO exhaust leaks.

My boost leak at my Intake Mani is still there but I'll get to it soon enough.

I pulled the car out today and it runs okay.I only have a few hours a week to work on it with my schedule so progress is slow.

I hooked up my NISTUNE and found something funny.

My car Rev's FREELY to 7.5K. The TACH rev's nicely.

I tried to do some logs, but when I went to check it out after the drive, the highest revs measured were 3.5K

Fuel Trims are about 13.5-13.8 all the way to 7K in 3rd gear with .7 Bar.

So, I think this may be the reason why may car is running like crap.

I'll have to confirm and see what's going on when I have more time, but that's what I found this week.

At this point, I just want an LS1....

[veloz]

Popped stock maps on the ECU for 555cc Injectors.

Still running at like 13.8 - 14 AFR at WOT.Car feels like it's running well now but AFR's are Stupid lean! If I didn't have a Wideband, I would think everything was okay.

Car does not Hesitate anymore which is good and pull nicely to redline.

I'll have my friend check my Fuel Pump Voltage tomorrow.

I also double checked that I had a good vaccuum line with no leaks to my FPR.

Very Frustrating....

On the bright side, it's running now.


Modified by veloz at 8:43 PM 4/13/2010

[surfer240]

im having a similar problem only my afrs are way leaner i jus got a wideband thinking i was gonna be on the rich side of the scale.... if i didnt have my wideband it would have been over! my f/p is fine 46 vac unplugged 36 otherwise raises when pedal applied, timing is on point... as soon as i give any throttle it goes from a 14.6 crusin to at least 15.1 at wot!!! ill feather the gas and when i go into it it leans. here is the kicker tho its on stock boost with a toob manifold, intake, exhaust and a walbro checked for vac leaks had one under the tb nipple on left had my vac gauge hooked up to my fpr line took that off, swapped my sr fpr for my friends ka24 fpr are they the same? didnt change anything anyways... one thing i did notice is if i have my key in the fuel pump wont shut off like it used to after a few seconds i checked my f/p and i hear it leaving the fpr but the fuel pressure is stabil on the gauge why would the pump stay on like that?

[240life]

Veloz, Well it seems like your almost there...I run into that problem usually 2 times a year after our spring and fall classics, and it is alway a g-dam stud and turbo to manifold gasket...thank god for wide bands. I hope you get your AFRs' corrected...probably somewhere in your tune.

[veloz]

Tested my Fuel Pump Voltage. My car reads 14V.
Fuel Pump Reads 12 V.....

Yeah it's low.

I'll try and trace to see if I can find the drop.
If not, I'll rewire the pump.

It's not the tune. Running on Stock maps.

Reason it's leaned out further is cause I fixed some boost leaks.

[veloz]

Rewired pump.

Straight 14V now.

Same issue. Still running lean.

FML


Adjustable FPR next.

[veloz]

So, I've ordered up the HKS -6an adapter for the fuel rail.

I'll have my new AFPR setup some time next week.

I also ordered up a brand new o2 sensor.
We'll see if it helps.

[veloz]

Fuel line adapter not here yet.

I switched mine up with a known good regulator and I still have the same issue.

I have a feeling my FPR will not be fixing the problem either.


Anyone have insight on this?
Anyone had a BAD AEM wideband sensor? Short of that, I don't know.

Thanks