ruled out fuel by replacing the fuel filter and testing my fuel pressure when it starts stumbling, replaced ignition control module, and ignition coil, opti is only 3 months old. it started doing it when it was snowing, let it sit for a day and cleared codes (and put on new fuel filter) and it was fine. rained the following day and it started doing it again. pulled off the opti and theres no moisture or anything of that sort. loctited the rotor screws even though they werent loose and cleaned the opti with electrical cleaner, still the same exact symptoms. i have a HPTuners log file from when i scanned it and its reading -26ish degrees of timing at idle and it goes more into the negative as the RPMs go up. id be more then willing to send the file to someone if they want to take a look at it but im stumped at this point. any help would be greatly appreciated.

 

The -26 is degrees before top dead center. It is right. The miss comes from the optical sensor not the cap and rotor usually. Have you checked to be the wires are not arcing?

 

yup theyre new as well. im thinking bad gas or the crank sensor

 

I don't think the cps can cause a stumble/misfire. Have you scanned it with an enhanced OBDII scan tool? That should find the cylinder(s) that are missing.

 

i was told it could by the engine builder, and yes i did and it just comes up as P0300 which is Random/multiple cyl missfire. i really dont wanna replace the opti this soon but i know they can be bad right out of the box so it may be the only solution

 

Make sure you didn't burn a plug wire. I did and gave me a bad misfire and P0300.

 

you might want to replace the coil wire

 

you might want to check your maf sensor it may be getting moisture on it. it seems to only happen when it is wet out. you might also check the opti vent hoses to make shure they are conected and not clogged.

 

checked, none burnt

brand new as of lastnight, changed nothing.

checked lastnight and everything is good. no codes and shes clean. opti vents arent clogged and are hooked up. also there was no moisture in the opti when i took it apart.

anyone else have any ideas lol

 

Check for vacuum leaks. A small hose on the side of the intake might have come off. It happened my mother's LS1 car so I guess it could happen to an LT1 car.

 

ehh i doubt its that only because it ran fine then messed up, then ran fine again and now its all fubar. ill check tho

 

For ignition purposes, the crank position signal comes from the Opti optical sensor. The CKP sensor on the crank is used to detect misfires, not set the ignition timing. There is a separate code for the CKP sensor.

Might want to add a "signature" with basic info about your car.... year, model, engine, trans and any major mods.

 

Did the scanner have "GM enhanced parameter" capability, as moparman suggested? If so, it can recall the specific misfire count, by individual cylinders. Not all scanners have that capability.

 

i was hoping youd chime in Injuneer, i used HPTuners to scan the car and thats all that came up. im gonna swap out the crank position sensor and check for bad gas and check plugs. beyond that im gonna have to swap the opti

 

I am having the same symptoms 86formula described. No engine codes but a stumble while driving. I recently replaced the cap and rotor too and my wires and plugs are all good. I checked fuel pressure and vacuum, those are good too.

I really dont know what else could be wrong, I will try the CPS and some dry-gas

The problem has been around for so long that I dont think its bad gas. I was starting to think sticky Fuel injector?
What do you guys think?