running to lean under boost

[ryancoke]

a new problem has occured, when i go into boost full throttle, it goes insanely lean, and backfires, and hesitates, the wideband is all over the place, and will go right to 20ish on the meter, but if i go say half throttle, or so it's better, some backfiring, but better, Now i have checked the injectors, the fuel filter, and TPS, and mass sensor, and it seems to be in working order. I have cranked the safc right up to the max settings, and right back down to zero, and no change on the wideband, or drivability. it just geos lean, if anyone has had this problem before, or could offer some suggestions, it would be greatly appreciated

P.s it's a KA24DET with sr370 injectors, safc, and stock everything else

Edit: i should mention that this started about 3 days ago, and progressivly got worse
Modified by ryancoke at 1:29 AM 4/13/2007

[rotorimp]

It has to be something like TPS, MAF, temp sender--something that controls fuel under load. How did you check the TPS?

[Edub1]

First, check plugs for carbon fouling, then pull codes and proceed as per FSM. You could have a bad injector of fuel pump too.

[NateDogg]

most likely you're experiencing spark blowout. install new plugs at a smaller gap, check your cap, rotor and coil voltage.

[ryancoke]

Well i checked the TPS's voltage read out with a voltage meter, and it's in spec, fuel pump is about 2-3 years old, and spark plugs are a week aand a half old, with a gap of .032

[Edub1]

I tried a .34 gap and my car wouldn't run worth squat. Unless you are boosting over 20lbs I would run the stock .44 gap.

[Chezedik]

At what voltage ranges did you check the TPS?

[NateDogg]

Check the fuel pump voltage at the connector at the fuel tank. It is common for the tiny stock wiring to dry up, especially with a high amperage pump.

Also, what do your spark plugs look like after this occurs? Just shut her down when it goes lean to see what you can see.

[ryancoke]

At what voltage ranges did you check the TPS?

i don't remember what range it was, cause it was late when i did it, but i believe it was in the .2-.10 range, it it speced out accordingly

[ryancoke]

Check the fuel pump voltage at the connector at the fuel tank. It is common for the tiny stock wiring to dry up, especially with a high amperage pump.

Also, what do your spark plugs look like after this occurs? Just shut her down when it goes lean to see what you can see.

Plugs look lean, good white color, and low if any carbon, i'm aslo running the stock fuel pump

[Chezedik]

What sort of multimeter are you using? I ask, because it seems to me that:1) Your closed throttle voltage is too low, it should be .4-.5. 2) You may have a bad spot on the wiper.

Sometimes, a TPS can fail on part of the wiper and so it will only freak out at a certain throttle position, for you this may be WOT. That is why I would check that. But before anything you need to reset your TPS to the correct location.

[Chezedik]

Oh yeah, check out your TPS at mid throttle and WOT, it should read something like:Mid - 2.5-3.5vWOT - 4.8-5.1v

If neither of those checks out, you have a bad TPS.

[ryancoke]

-------------------------------------------------------------------------------- O.k so managed to track down the problem, it was a timing issue, but with that said, it still runs lean, i have the safc cranked up to like +50, and still no change, that and it seems to be struggling real hard to get to redline, ( from idle to 4000rpm, pulls great, then from 4000rpm on, it has no jam, and will actually stay stuck there for a while like having a plugged exhuast), i beleive the timing is set at 16 degrees now, but thats only a rough guess cause my idle won't go down to 750ish when i unplug the TPS, so it's probabaly still advanced somewhat. any ideas??

Edit: it leans out progressevly from 3500 onward( like 12.1, 12.2, 12.4, 13, 14.5,15 and so on)

[DammitBobby]

1st You need to install a fuel pressure gauge. At idle it should show around 34psi.

2nd You will need to monitor fuel pressure under load to see if is still holding and going up 1 psi per pound of boost.

My guess if you checked everything else and have found nothing it is either a clogged fuel filter or bad fuel pump.

I had the same problem with my stock pump as soon as you would go into boost it would hesitate and buck around. The old fuel pump worked fine before I started boosting. I was able to determine it was a bad fuel pump because the fuel pressure gauge would fall to zero pressure when I turned the car off. It is actually suppose to hold the pressure for a while before completely going to zero pressure.

Good luck.

[boriquaS13]

Sounds like you need to upgrade your fuel pump. You could have good pressure not enough volume or supply. Hope this helps good luck.

[ryancoke]

Yes i will be buying a walbro here very soon, it actually may seem to be the pump, as it starting to sound a bit funny.

[Chezedik]

****, I assumed you had a high flow pump.

[WDRacing]

The SAFC shows TPS voltage. Get a fuel pressure gauge like suggested.

How much boost are you running? What turbo, what mani, what size DP etc?

WD

[ryancoke]

The SAFC shows TPS voltage. Get a fuel pressure gauge like suggested.

How much boost are you running? What turbo, what mani, what size DP etc?

WD

10psi, t-25 turbo, SSAC bottom mount manifold, 2 1/2 down pipe

[WDRacing]

The T25 is far to small of a turbo. The stock fuel pump sucks@$$. You need to figure out EXACTLY where your timing is.

That turbo is way out of range at 10 psi...back it down to 7-8 at the most.

WD

[ryancoke]

So problem fixed, it turns out my fuel pump is junk, and i needed a new one, so for now i have a inline fuel pump feeding my injecotrs untill my walbro comes in