Hesitates, no power, stumbles, runs sh*t rich

[LS1toSVT]

Ive been dealing with this $*** for a month now... and Ive had it.

Mods: whipple 3.0 pulley, 60's, K&N, MAFia, BAP, Accufab, o/r xpipe, flowmasters.

Car ran solid for a month with that setup. One morning I started the car and noticed the hesitation when starting off in first gear. Problem gradually progressed to constant hesitation, power loss, stumbleing.

Problem:

o2's are pegged(.98ish) at idle, fuel trims are pegged at -25% trying to pull out fuel. ALL plugs are black, car hesitates at any rpm, stumbles under boost. Lacks ALL power.


Checked so far:

MAF's were switched
new tune was written without MAFia
EGR system was removed
No vac leaks
TPS is set at .99
IAC was removed/cleaned
FRPS was replaced
No misfires
Brand new PCM was installed
FPDM was swapped with a working unit
Plugs were replaced, now they are black
Fuel filter was changed
switched tunes

Fuel rail pressure is normal
ECT is normal
IAT's are normal
TPS is normal
VAC is normal


I dont know what else could cause my car to run like this. The problem went from random, meaning it would hesitate, then 20min later run perfectly fine, to constantly like this.

[Viper_ed]

Have you tried bypassing the BAP? Maybe something is causing it to max out the FPDM. Did you cut or shorten the RCA Cable that runs to the switch for the BAP? I know that there is a certain resistance value that the BAP sees from that switch that has something to do with the length of the wire.

I'd also try running it with the stock injectors instead of the 60's. Maybe something is either wrong in the tune or you may have an injector hung open or something like that.

[Wolfpack Speed]

double check your o2 connections and verify your sensors are good. your symptoms are exactly what happens when the o2's are bad...good luck!

[LS1toSVT]

double check your o2 connections and verify your sensors are good. your symptoms are exactly what happens when the o2's are bad...good luck!

I will look into that. Is there any way to test the o2's? They do move/sweep during part throttle/cruise speed. And when I pull a injector harness off the driver side, that o2 leans out. So Im assuming they are reading whats actually going on.


Have you tried bypassing the BAP? Maybe something is causing it to max out the FPDM. Did you cut or shorten the RCA Cable that runs to the switch for the BAP? I know that there is a certain resistance value that the BAP sees from that switch that has something to do with the length of the wire.

I'd also try running it with the stock injectors instead of the 60's. Maybe something is either wrong in the tune or you may have an injector hung open or something like that.

Bypassed the BAP. Swapped FPDM's. Didn't touch/modifiy the RCA cable or BAP. I tried different tunes from different tuners, also with a brand new PCM. And the problem is global, as in all 8cylinders. So if one injector was stuck, all 8 plugs shouldn't be going black. Correct?

Keep em coming guys. Anything you can think of.

[Chris00GT]

I'd remove the chip/tune go back to stock and install the stock mass air meter and injectors and see if she runs better.

Hmm this one even has me stumped. You've replaced or checked most things that we'd look at The only other thing is do a leak down and compression. M t with it being radom it has to be an electrical gremlin. Didn't you have the car down at our shop(Kauffman Motorsports) to have us try to figure it out?? Sorry we get alot of car with problems and it's hard to remember.

[LS1toSVT]

I'd remove the chip/tune go back to stock and install the stock mass air meter and injectors and see if she runs better.

Hmm this one even has me stumped. You've replaced or checked most things that we'd look at The only other thing is do a leak down and compression. M t with it being radom it has to be an electrical gremlin. Didn't you have the car down at our shop(Kauffman Motorsports) to have us try to figure it out?? Sorry we get alot of car with problems and it's hard to remember.

The mass air meter is stock. I just have a MAFia. Also, I tried 3 different tunes. I can definitly say its not the tune/PCM. I was thinking about going back to the stock injectors, but I need 60's for my setup, and I can't see all 8 60's going bad on me. It has to be something telling the 60's to run rich. Last resort will be going back to the stock injectors/tune.

RWTD sent me a tune that disabled the LTFT's and the "adaptive stratagies" in the PCM. I then logged the car at 500rpm incraments for 15seconds. Sent them the file and they went over it. James from RWTD confirmed that the tune is solid. But the car still runs like crap.

And your right, I've checked/replaced damn near everything possible. The only things I haven't swapped out are the TPS(which is showing proper voltage), the o2's(which respond accordingly from what I can tell), the injectors(which can't ALL be bad).

I haven't brought it to Kauffman's, but thats not out of the question right now. I may have a new friend(thanks PJ) that may be taking the car off my hands and is going to try to trouble shoot it in his free time. Because right now I dont know what else to do. I can't afford to just keep replacing things that aren't showing up as a problem. I have a new FPDM on the way to my house, and thats been ruled out already. Anybody need one? lol

I hate the world right now.

[Chris00GT]

Another thing that I'd also check is the crank postion sensor. If it's gone bad the computer doesn't know when to fire the injectors at the right time. When mine started to go bad it would jerk and back fire and slowly got worse. It tripped no check engine light. Just another possible cause.

[LS1toSVT]

Thanks. How can I check that? Where is that located on the block? Also, at idle, my timing sits around 20, is that normal?

[Chris00GT]

I'd pull it out and look at it and check for cracks, but honestly mine looked fine. It's located at the bottom passanger side of the timing cover. With your car being an 03 cobra it's going to be easier to see it from under the car. And your also going to have to remove the 3 bolts that hold the A/C to the block so you can swing it out of the way so you can remove the crank position sensor.

[Rodeheaver's]

sounds like the fuel pres. reg might have taken a dump, pull off the vac line at idle and see if fuel is coming out, also, check fuel pres, does the car seem to be blowing any smoke at all? and what is your plug gap, i know you changed them but with the smaller pulley you may have to tighten the gap... and also i find it ness. for top performance, to keep the maf really clean, meaning i spray a little "air intake cleaner" on the sensor itself and wipe out the inside of the case... just my 2cents

[LS1toSVT]

Thanks for the reply, and trust me, everyones 2cents means alot right now because I'm all out of ideas.

Car isn't blowing any smoke. I changed the frps, and the frp is normal at idle.

Cleaned my maf and swapped mafs.

Plug gap is at .35, which is where my tuner suggested.

[Viper_ed]

Plug gap is at .35, which is where my tuner suggested.I'm guessing you meant .035. Don't think the gap is causing your problem though. I'd suggest gapping them at .028 though.

[Wolfpack Speed]

Thanks for the reply, and trust me, everyones 2cents means alot right now because I'm all out of ideas.

Car isn't blowing any smoke. I changed the frps, and the frp is normal at idle.

Cleaned my maf and swapped mafs.

Plug gap is at .35, which is where my tuner suggested.
did you swap your o2 sensors yet???????????

[LS1toSVT]

did you swap your o2 sensors yet???????????

2 new o2's and a new MAP sensor are on the way to my house. After that I dont think there will be many sensors left!:hissyfit:

[Wolfpack Speed]

2 new o2's and a new MAP sensor are on the way to my house. After that I dont think there will be many sensors left!:hissyfit:#1 or #2 sensors???????????

[LS1toSVT]

I only have the front 2. Rears are gone.

Also can someone try this test for me?

Plug in your predator, key on, car off.

Under "gas fuel" look at your BARO reading, the very first one (on mine anyways)

Then start the car and see if it changes at all. Also scroll down and look at the reading called FPM, it has a ON/OFF reading. See if it constantly switches from ON to OFF about every second or so.

My BARO stays at 28.1 car off or on. Also stays there when I unplug the sensor on the back of the blower base. Something tells me that the MAP sensor at the back of the blower doesnt record the BARO.

[LS1toSVT]

Never mind. The map sensor is fine... the baro isn't supposed to change.

But can someone look at that FPM value on their predator for me?

[Rodeheaver's]

check your fuel pressure!!!

[LS1toSVT]

Thanks, fuel pressure is normal. Also swapped FPDM's and removed BAP and installed a new FRPS. The fuel pressure is normal.

[LS1toSVT]

The one and only thing that looks off is the TPS %. A friend of mine has a scanner that shows tps voltage and tps %. The TPS % is at 14% at idle, but the tps is set right where its supposed to be at .99. The only way I could look further into this would be to check someone elses cobra.

[00blackSS]

Still not running right yet?!? damn u need a hand with anything let me know

[LS1toSVT]

Still not running right.

Can someone check another thing for me on their predator? The reading should be about 1/2 way down under "fuel"

Check the Throttle position mode, at idle mine has a "?", at part throttle it says "WOT" and when I go WOT it says "P/T"

Could someone please check this out on their car for me? Thanks guys.

[Stangman701]

That sounds like it might be part of the problem. I'll try to remember to check mine at lunch time :goodidea:

[LS1toSVT]

Thanks man!

-UPDATE-
Just to put things in a little better perspective, Im going to try to explane what I think is going on. Keep in mind I still have NO clue whats causing it.

So, the cars running shit rich. All 8 plugs are black, so there is my physical proof. Both O2's are pegged at .9x at idle, and the fuel trims are both at -25% at idle. This means that the O2's are reading the rich condition, and are telling the computer to pull fuel.

According to my predator, there is no indication that the computer thinks there is a load on the engine. MAFv is low, LOAD is at 17-20% at idle which I was told is normal, TPS is at .99(even though the TP mode says "?" which hasen't been sorted out yet) fuel pump duty cycle is low, and the FRP is at 38-39.

SO lets say all the sensors are reacting/reading properly. Could the computer by acting up and sending the wrong signal to the injectors causing a rich condition? Doubt it, because the computer was replaced.

Vac leak? I can't see how. Its my understanding that a vac leak would cause unmeasured air to enter the system, causing the o2's to read a lean condition, which would then show the fuel trims adding fuel to compensate, my symptoms are the opposite.

EGR is gone, and the EVAP hose has been removed from the blower. Neither have helped.

So thats where Im at right now. I've ruled out just about every sensor on the car, and can't think of any other mechanical situations that could cause this...

[Stangman701]

I just checked it man, mine says the same thing... the search continues :frown:

[Twin01cobra]

I'd maybe check for a broken wire or maybe a wire is shorting out somewhere. Just a thought.

[LS1toSVT]

I just checked it man, mine says the same thing... the search continues :frown:

Man, thats the LAST thing I wanted to hear... Thanks alot though man, I appreciate it.

As for a shorted, damaged wire, how can I check for this?