fuel cut I have no idea whats wrong. help

[Merkles]

I have no idea what is wrong with my car. My mods are listed in my profile. Here is my problem. My car rips until 15psi where I have my boost set and holds until anywhere between 4500 and 5500 rpms then hits fuel cut. I have no clue why. I ran a boost leak test and had 1 tiny leak at the throttle body but I fixed that and I changed my spark plugs and put new ones in. Any ideas?

 

[DSM_PWR]

Hmm... well ive had this car for 11months now and havent changed it. But today ill be changing the coilpack and transitor and ill try using my friends battery to see if that helps

 

[DSM_PWR]

So i can rule out the coilpacks, changed those yesterday and still did it... ill try the battery tommorrow

 

[Merkles]

Make sure the connectors are clean on the battery too.

 

[v8s_are_slow]

Check your grounds also. I'm having a sputter problem right now but I know for a fact it's my plug wires. Yesterday I went to the track but didn't think about what I was doing when I added some 110 octane. It definately made it harder to ignite the fuel and started sputtering really badly. Can't wait to get some 93 back in. As for me, I'm NOT gonna be going cheap on plug wires. It was running great at 25psi on 93 and then my dumbass had to put a higher octane. Tard. Track was wet anyway though so no biggie.

 

[DSM_PWR]

ok so i THINK i FINALLY fixed the probelm today, the GM MAF...

I swapped my 3' for my friends 3.5' GM Maf and i was able to redline at 17psi. However now it leans out bad.. as low as 17:1 by redline. I cant seem to figure out the settings on the MAFT for the 3.5'.

I sold my SAFC so all i have to tune with is the MAFT... i know the 1st one out of 4 switches has to be up but what else do i mess with??

 

[v8s_are_slow]

With the 3.5" maf, the number 1 dip switch needs to be on, the rest to off.

MAFT Version 2.0+ Tuning Guide - Full Throttle Speed Tech Support

Then just get your base and aux knobs set to the injector size you have and keep the low, mid, and high all to 0. Fire it up and watch your wideband. If it's way lean or rich, start adjusting the base or aux until it gets close to where you need it to be. Then drive it around and adjust the rest to fine tune it. It's not bad at all.

 

[DSM_PWR]

Hm... im having the hardest time tuning w/ the maft. my WOT issues are finnally over
but very very lean by redline 17:1 eek!!

it seems as though i can get a steady cruise (MID). The injector setttings for 650cc seem to just lean it out so i have it set to AUX 5 and everything else zero out so i can get a sorta drivable state. idles at 15:3.. i hate MAFT so i think im just gunna buy an AFC really quick and just zero out the maft. Hoping DSMLink v3 comes out next month so i can sell them both

 

[v8s_are_slow]

The GM Maft is cake man. But keep in mind that just because you have it set for 650's that that's where your base and aux needs to be. Set it according to your wideband to get it close. If it's leaning out only at redline, you might wanna richen up your high setting and see if that helps. But if you're familiar with an afc, it might help to zero out the maft and use the afc along with it.

 

[DSM_PWR]

K, well thanx alot v8s!
I appreciate all your help and i recommended you for "Reputation Points"

 

[v8s_are_slow]

No problem man, and what I meant to say is that although you have it set for 650's, that doesn't mean it's where it's suppose to be. Set if for 650's and then adjust accordingly to what your wideband says, not by what the graph of numbers says it should be.

Personally, when I 1st got this current car, it was really rich and with 2 clicks, it was right where it needed to be. You can add or subtract a bunch of fuel with the base and aux knobs. The low, mid, and high knobs add or subtract in 5% increments.

 

[DSM_PWR]

son of a b****, it did it agian, it seems as though its having trouble holding boost!!!

Really starting to piss me off to where i just wanna sell it...

 

[Merkles]

Do you think maybe the ecu could be messed up?

 

[DSM_PWR]

i hope not... hmm ima have someone look at the timing and see if maybe it jumped a tooth or so..

 

[Merkles]

Mine did it again tonight, let me know how the timing is. I just got my socketed ecu in the mail, my bigger new injectors are on the way and this week I am ordering my keydriver chip from DSMchips. If that doesn't fix the problem I am going to try seafoam. Maybe there is a carbon build up. highly unlikely to cause this but its worth a try. Lol it has to be something and between me and you we have covered most of the engine bay.

 

[DSM_PWR]

i havent had a chance to check timing, but for some reason i cant help but think its a boost leak somewhere underneath the intake manifold or something?? either way i just ordered a JM Fab SMIM and 1g TB so when i install those ima pull out the motor and clean around/rewire/relocate a few things so I HOPE!! it will go away

 

[randyknightjr]

i have a 92 laser RS and i had the same "brick wall" feeling in my car. this is all that i did to fix it. first i have to say i have a 3" MAF with a translator, 650cc injectors, fuel pressure regulator and 255 lph fuel pump. first i thought it was the fuel cut, so i bought a HKS fuel cut defender. the problem persited . then i put the cam timming back to stock setting ( thinking i had it too advanced) i still had the cut, so i adjusted the cam timming back to where i had it before because it wasnt the problem. then i made sure the MAF translator injector setting was set right for 650cc injectors and that the mid and WOT settings were set to zero or(no change) setting, and it was set correctly. so i started thinking and ran my own test, i adjusted the mid and the wot settings to one click leaner. and it went away. problem fixed.

i also noticed a diffrent problem a week or two later. sometimes when i was under hard exceleration the car would studder innermitionly. i checked alot of things before i found that the connectors to my translator were loose, i tweaked the male pins and put a tiewrap around the connetors to keep them tightly connected. also thats when i found out that if u disconect the translator from the car harness for more than a few mins, the translator thinks whatever setting its on is the zero setting. there for whenever i disconect it to do some work i have to turn all the dials back to zero after i disconect it, and after i reconnect it i must turn the key on and set them back to the proper settings. it may not be the same for you translator but mine is that way.

 

[mmmmbst]

But what if you have this same problem with the sputter and no MAFT or GM MAF? Ive been stuck on this problem for like 8 months and strapped for cash. I thought it was an ignition problem too. A/F dropps down to 10. I kinda gave up an now drive the truck everyday. But i think this thread made me want to try to fix it again. Anyone have any ideas?

Also my mods........
2.3 stroker
Big 16g (internally gated)
660cc injectors
walboro 190
magnecore 8.5 wires
NGK br7es (go through them like water)
SAFC
Wideband 02
and more in my profile....

any help would be greatly appreciated

 

[Merkles]

I have the stock 2G MAS as well and this is happening to me

 

[randyknightjr]

thats too rich of an air fuel mixture. remember the lower the number the richer it is. ## car is running too rich on the top end thats why it is cutting out. i will sen you a PM.

 

[Merkles]

I went to advanced auto today to use the diagnostic tool and here is what I came up with"

At idle with the car warm:

TPS = .4%
Load = 18%
Coolant = 214
IAT = 126
Timing = 5-6 Degrees Advance
LT FTRM1 = 12.5%
ST FTRM1 = 17.5%
Fuel = Switch between Open/Closed
O2S11 = .02V
O2S12 = bounced around sometimes high sometimes low
LT FTRM12 = 5.5%
ST FTRM12 = 5.5%


Can someone help me out? Once again my car is accelerating then hesitating or misfiring for a split second then pulling to redline. Do these values look fine? I think my one O2 sensor is messed up with the constant voltage at .02V

 

[DSM_PWR]

i got a check engine code today while driving, P0170 "Fuel trim malfunction (Bank 1). I remember getting this code a bit before i started getting the whole problem. But as i recall i think it was because i was running to rich? thats what triggers it correct??

Right now my idle is extremely lean, around 17:1 and lower, no matter what i do to the SAFC or MAFT, the idle wont stay stoich for to long.

EDIT: found out my wideband was reading a lean idle because the dp gasket was blown eek!

 

[randyknightjr]

to merkles

to try to answer that you will first have to know how a narrow band o2 sensor works (assuming that you have a narrow band)

Technically narrowband oxygen sensors produce an oscillating voltage signal, When the air/fuel ratio is perfectly balanced, a narrowband O2 sensor produces a signal of ABOUT 0.5 volts (500 millivolts). When the fuel mixture starts to go rich, the O2 sensor's voltage output will move twards its maximum output of close to 1.0 volts. Conversely, when the fuel mixture starts to go lean, the sensor's output voltage will start to drop twards 0.1 volts.


so based on my first statement of the oscillating signal, and yours did not change i would say that the front o2 sensor is bad. unless you were looking at freeze frame data.

 

[Merkles]

Put my Eprom ECU with the keydriver chip and my Denso 720's in today. Car is running great so far, no issues as of now. I'm most likely still replacing that O2 Sensor though, its pretty much shot.

 

[v8s_are_slow]

Good to hear. Hope we don't hear "I'm still having problems" in a couple of days. Lol.

 

[DSM_PWR]

aw man, i really wanna wait for DSMlink v3 to upgrade fuel controller...

either way i swapped out my ECU with my sisters GST and still does it