Lean Misfires at 2700-2800 rpm

[TurboBob]

perhaps his issue is not fuel. If adding fuel doesn't clear it up, and you are sure fuel is actually being added, then the trouble is elsewhere.

Use MMCd to log the scanmaster at 57.6K baud and log a ton of stuff, creep up on the condition and creep thru till it clears up so we can see what happens at the thresholds.

BTW, ignition troubles will cause this kind of crap and are tough to find....

Bob

[badass3000]

Originally Posted by keithmac

Badass, have you added fuel in at the point of missfire?, mine`s been working like a charm, hits 15.5:1 where it would have been >16:1 and missfiring on the stock map..

I have a dyno graph that shows I am at 12:1 at 2700rpm. Of course thats WOT but theres no way that is a lean missfire.

Ill work on a log...

[badass3000]

alright, everytime I record a log the car seems to act fine.
I guess my car knows when its being recorded?!.

[jwetzler]

Originally Posted by badass3000

alright, everytime I record a log the car seems to act fine.
I guess my car knows when its being recorded?!.

Mine did the same thing. When I would plug in the data logger cable to the diagnostics port, the stuttering and hesitation would go away. As soon as I unplugged the cable from the diagnostics port, it would come back all of the sudden. No one seemed to have an explanation for that lol.

[keithmac]

Wierd, maybe having the ECU in diagnostic mode alters the fault?, Badass is your fault at WOT?, it`s in a totally different part of the map at light throttle so WOT readings don`t really show much. Mine was awful at light throttle openings around 2800 rpm.

[badass3000]

just a thought, as I am still fighting this.
has anyone tried unhooking their A/F gauge?
Im not saying "if I cant see it then it must not be doing it" but that these A/F gauges are "active" and if you dont use both +12vdc and ground then you will be throwing weird signals (ie +5vdc as a NB reading) to the ECU, they are seen by a logger but what if they werent seen?

Reason I thought that might be the case (turns out negitive) is bc I knew I unhooked both my O2's but was recording a normal looking signal from my rear O2 sensor, turns out my gauge was hooked up to the rear and was somehow making up a voltage (even w/o +12vdc going to it) that simulated a working O2!!!! HOW??

Anyway, unhooked gauge, zeros for both O2's.
go for a ride, felt fine at first, then two min later its back.
This time a make a log!!
Im looking at the log and dont notice anything weird,
other that a strang ACLE graph, but mabey its normal?
Its never below 50%, then jumps to 100% when ever TPS increases.
Does that sound right to anybody? Shouldnt it be below 50% sometimes?

I cant upload my logs but here are the ranges of each sensor for the 2 min log.

RPM=1000-4000
INJD=2.0-13.0
KNCK=0
O2-R=0.01
O2-F=0.03
TPS=25-100
MAP=-8 to 2psi
TIMA=25-37
COOL=189'
AIRT=105-113
INJP=1-6
BATT=13.7
ISC=42-67
**VSPD=0-100 ossilation???
FTRL=100
FTRM=100
FTRH=100
FT02=100
MAFS=94-407Hz
**ACLE=50-100 steps???

[J-Ville VR-4]

Originally Posted by badass3000

just a thought, as I am still fighting this.
has anyone tried unhooking their A/F gauge?
Im not saying "if I cant see it then it must not be doing it" but that these A/F gauges are "active" and if you dont use both +12vdc and ground then you will be throwing weird signals (ie +5vdc as a NB reading) to the ECU, they are seen by a logger but what if they werent seen?

Reason I thought that might be the case (turns out negitive) is bc I knew I unhooked both my O2's but was recording a normal looking signal from my rear O2 sensor, turns out my gauge was hooked up to the rear and was somehow making up a voltage (even w/o +12vdc going to it) that simulated a working O2!!!! HOW??

Anyway, unhooked gauge, zeros for both O2's.
go for a ride, felt fine at first, then two min later its back.
This time a make a log!!
Im looking at the log and dont notice anything weird,
other that a strang ACLE graph, but mabey its normal?
Its never below 50%, then jumps to 100% when ever TPS increases.
Does that sound right to anybody? Shouldnt it be below 50% sometimes?

I cant upload my logs but here are the ranges of each sensor for the 2 min log.

RPM=1000-4000
INJD=2.0-13.0
KNCK=0
O2-R=0.01
O2-F=0.03
TPS=25-100
MAP=-8 to 2psi
TIMA=25-37
COOL=189'
AIRT=105-113
INJP=1-6
BATT=13.7
ISC=42-67
**VSPD=0-100 ossilation???
FTRL=100
FTRM=100
FTRH=100
FT02=100
MAFS=94-407Hz
**ACLE=50-100 steps???

I think if you change the log files to .jpg or some other format the forum accepts then you can post it up. Did you ever get a good TPS? I remember something about yours was screwed up, I think it was the idle switch?

[LUSTFUL]

that and it looks like you recently reset the ECU as well judging from the 100% fuel trims across the board. HAve you tried driving the car to acquire a set of fuel trims first before you dismiss it as the ECU entirely. I know my car drives like shit when it is on a fresh reset, up until it starts to develop a new set of fuel trims

[badass3000]

Jake, yeah TPS switch is bad, but I dont think that could be it.
I bought one from someone, but received a TPS that had only 3 pins, and guess what the missing pin is wired for, yep the idle switch.

VSPD is vehicle speed???
its jumping around faster than an O2 sensor at idle!
whats that all about?

I remember hooking up a water temp gauge around the time this started. Could the sensor that I unhooked be in any way related to this???

[J-Ville VR-4]

Originally Posted by badass3000

Jake, yeah TPS switch is bad, but I dont think that could be it.
I bought one from someone, but received a TPS that had only 3 pins, and guess what the missing pin is wired for, yep the idle switch.

VSPD is vehicle speed???
its jumping around faster than an O2 sensor at idle!
whats that all about?

I remember hooking up a water temp gauge around the time this started. Could the sensor that I unhooked be in any way related to this???

I havent put too much thought into your problem and how it could be related to a bad tps, but off the top of my head since the idle position switch is bad the ecu might somehow think the throttle is at idle when its really not. Chances are this is nothing, as the ecu still has the tps step counts to go by, but I'm just thinking out loud.

And as for your vehicle speed, I really doubt that matters, considering mine has been FUCKED for years now - my turbo timer is wired into my speed sensor, so it reads the signal and outputs my speed in kph. Sometimes (rarely) my speedo works normally, most of the time I see 0kph no matter what speed I'm going, and most of the time the speed will bounce around crazy, reading anywhere from 0 to 399kph. When the reading is bouncing around on the turbo timer, usually my speedometer just sits at 0mph. Sometimes on the turbo timer it sticks at 399kph too. The even weirder thing is that sometimes my speedometer will read how it should, yet the kph reading on the turbo timer is bouncing around. So the speedo and turbo timer dont respond the same, even though they are both getting the same input signal. I havent datalogged my car in ages, but I think it read crazy too. I just dont care since my car still drives fine. But what I'm getting at from all this is that since the screwed up vss readings dont affect my driveability, then I would assume they shouldnt affect yours either.

Does your speedo work right?

Since we are now basically guessing as to what the problem could be, why not try and unplug the speed sensor at the trans and see if anything happens. I think you might get a check engine light and a code, but just ignore that for the time and see if unplugging it helps fix the misfire.

And as for the water temp gauge, I trashed my stock water temp gauge and sender and installed an aftermarket one too, with no ill effects on driveability. The stock water temp gauge sender isnt even seen by the ecu anyway, it has its own water temp sender so its not part of the problem either. And since your datalog shows 189 degrees, then yours appears to be working correctly.