LS1 not running need help

[Camarokid08731]

Ok i need help in a big way. My car seems to run fine and then it feels like a few cylanders die and it richens itself out. then itll idle like its got a monster cam in it and stalls. when it stalls it shoots fire out the exhaust and makes a huge backfire that sounds just like a gun shot. then ill let it sit and itll start up after it cools down a bit. sometimes itll just fix itself. wich is why i beleive it is a sensor of some sort. it also happens worse in the cold and rain. If i give it gas itll sputter backfire and stall. Please help here are the mods list
Ls1 with 90k on it
Stock 4l60e
Stock Gears
Flowtech Longtubes with catless flowtech y pipe.
Flowmaster Cat back
The 02 sensors are the stock ones out my stock manifolds and are delcos
I have a LS6 manifold
Im running TR6 plugs because im planning on spraying it down the road
Ported throtle body
MSD wires
Timing is at 26 degress total
Any advice is greatly apreciated

[NJ Torque]

Check your 02 sensors... make sure the wires are not burned agenst the headers.

Also, try and unplug the MAF to see if it worsens...

[Camarokid08731]

yeah ill give that a shot i replaced them though nothing seems burnt any other theories?

[SRGN]

Would be a lot easier with some scan tool data. Even with no codes, could be an in range failure of a sensor. For a wild guess, I say coolant temp sensor not reading proper temperature at all times due to faulty sensor or wiring, and providing cold start enrichment to a warmed up engine.

[V]

*shivers* im having flashbacks of my catastrophic engine failure....

[Camarokid08731]

great....lol

[Camarokid08731]

oh and i already replaced my coolan sensor when it died on my at the track this summer also when the car acts that bad i have no tach reading

[98tadriver]

check engine light on? is it throwing any codes? check your EVAP lines under the hood. it plugs into the driver side of the intake. if any of that is loose, it will idle like it has a cam and run crappy after a while.

[Camarokid08731]

the code i pulled was 02 sensor heater circuit not working thats another thing i found out in my diagnostics ill have a scanner on her tomorow night for more data loging

[98tadriver]

good stuff. youre off to a good start. scanners for the win!

[Camarokid08731]

yeah hopefully itll be ok nothing serious its gotta be a sensor of some sort i hope because like i said itll magically fix itself sometimes

[Camarokid08731]

anyone else have any ideas?

[V]

does it get better or worse weather dependent, like rain/water?
at one point i had the JET plug in module for the ECM... it moved the connector out far enough that the wires rubbed on the hood hinge, wore through and when they got wet... my car went insane. TCS on and off, abs, misfires etc

[Camarokid08731]

it does it really bad in the rain and the cold

[Camarokid08731]

cant figure out why the tach becomes inop during the misfires either...

[V]

ill post more ideas/things to check tomorrow, right now im tired and a lotta stuff going on here, roommate going to afghanistan tomorrow. and in my engine failure, diesel fuel in my gas was the cause, so dont worry.

[Camarokid08731]

alright thanks bro i feel better about the engine failure now lol talk to you tomorow night when i get the scanner on her ill post the data log info

[Camarokid08731]

jus throwing the idea out there crank position sensor would throw a p0300 code if it senses a misfire now if that sensor is not reading correctly wouldnt it make the car run horrible and backfire?

[Jersey_TA]

Check the plugs. I had a prob like that recently with my vette. Check the grounds on the PCM and also check the fuel pump/filter.

[NastyEllEssWon]

when your car misfires it dumps fuel out the valves that didnt get burned and it burns up in the exhaust and backfires.


id check everything along the lines of the PIP (proper ignition pickup) which would mean everything in the ignition system....from the coils to the cam sensor to the crank sensor and back again.

sounds like you need a DVOM and start testing voltages and resistances of your sensors...unless you like throwing parts at a motor

[1_BAD_NBM_SS]

sounds like a Crank Position Sensor. Def check the PCM and the Fuel Pump. Just take the pressure line off the fuel rail and put the hose in a cup and turn the key to run, DO NOT START. Just to see if your getting any fuel!

[Camarokid08731]

im leaning in the direction of the crank sensor due to loss of tach ill keep you all posted goin to work on it right now

[sweetbmxrider]

well does that tac completely drop off? or does it drop down because your idle went to crap? also, you said you had an 02 code. did you fix this?

[Mike]

you probably just need to change the opti...........................

[Camarokid08731]

my cars coil on plug....its an ls1...and the tach shuts completely off when the car misfires

[Mike]

my cars coil on plug....its an ls1...and the tach shuts completely off when the car misfires

oh i know, it was a joke

[Camarokid08731]

oh lol ok i thought so

[sweetbmxrider]

so your car runs like crap but if you let it cool down it "fixes itself"
you have a code set for an o2 heater circuit malfunction
did you address that problem yet?

[Camarokid08731]

no i havent yet but the 02 circuit wouldn't make me loose my tach signal but ill have more info in about an hour on the issue im currently under the car on my sidekick

[NastyEllEssWon]

id be willing to bet its the crank sensor. after awhile sensors get old and a common occurance of a crank sensor going bad is seemingly random stall outs and ignition problems. once an old crank sensor gets hot it ''blacks out'' and loses functionality until it cools back down again and ''wakes up.''

[Camarokid08731]

Ok i fixed it turns out that when i installed the headers a few months back the harness for the crank positon was next to the header. the header melted the harness. so i re wired my harness cut out the bad section and re wired it. then wraped it in heat resistant tape.

[NJ Torque]

told you it had to do with the headers.

they absoultly suck on these cars.

[JL8Jeff]

Put some new O2 sensors in the car as well. If you had to hit the sensors hard to break them loose from the manifolds you most likely damaged them. And if they're the originals with 90K miles they should be replaced anyway.