P.O.S. RS

I hate to do this and ask for help, but I'm finishing up my LT1 swap into a thirdgen and i cannot seem to solve my issues with the car misfiring when it goes into closed loop.
The car has lots of new parts in it, brand new taylor plug wires, ngk tr55 plugs, optispark that has 0 miles on it although it is about 3 years old. I took the cap off and it was dry, everything looked good although there was some black carbon buildup in it. cleaned it all out. msd coil, new injectors, swap wiring harness was built from scratch by me, checked the resistance of all wires when i finished and everything seems good.

The car runs fine in open loop when cold, no shake, idles smoothly, has good throttle response, no backfires. but as soon as it hits closed loop, the car starts missing, shaking badly, and generally running like garbage. all of this is with the car in neutral, as its not smogged yet and cant really do any road testing without risking getting pulled over and that kinda stuff( not good on a car with 7 year old tags)
I just replaced the 02 sensors with new ac delco ones this morning and the problem persists. I also tried an extra PCM i have laying around from a caprice, and the car ran better in closed loop but worse overall, trying to idle at 600 didnt feel very good. also, the car doesn't seem to be throwing any codes.
02 sensor wiring has been checked and everything has continuity to the pcm and the heating elements are getting 12 volts with good grounds with the key on.

I use scan 94/95 to check on things as it runs and the o2 sensors still are giving me strange readings as soon as it goes into closed loop. one will be very low(under .015) and the other bank will be around .950 or so. I am massively confused and really desperate to get this thing running nicely in closed loop. Any suggestions would be greatly appreciated, i wont discount any advice given, i need to get this darn thing finished.
Attached is a short run from cold to a little after the closed loop switch from scan 94/95 if anyone can help. It is an excel file( the engine goes into closed loop after row 1557)
Thanks in advance!

AdsoYo

iTrader: (1)

Well you definitely have a fuel issue on the driver's side. Your O2 mV are fine until closed loop kicks in but the injector pulse is also longer than the passenger side. Once closed loop starts your injector pulse gets even longer but the O2 mV take a nose dive. The PCM is delivering as much fuel as it can on the drivers side. Your long term trims are maxed at 160 and your short term trims are maxed at 194. Your passenger side isn't perfect either. Even though the long term trims are at 128, the shorts are bottomed out at 62 so the PCM is having to pull fuel there. Then there's is a period of time where the IAC counts are zero, that's crazy.

At first I was thinking your hardware is fine and this is tune issue but seeing how the O2 sensors are reporting a ton of air relative to fuel and your injectors are staying open for so long, now I'm thinking you might have a vacuum or exhaust leak or a stuck injector.

P.O.S. RS

Thanks for taking a look for me. I appreciate the advice.
I will double check for vacuum leaks and exhaust leaks tonight or tomorrow when i get a chance, I will probably pull the intake and try to seal it up as best as i can again.
The engine is completely stock except for some short tube headers that have all the provisions for EGR and AIR systems. i couldnt seem to find a gasket for the header to EGR tube connection on the passengers side so i made my own out of some asbestos material i had lying around that might be a possibility for an exhaust leak.

I see what you are saying about the drivers side getting too much fuel and the injector pulse length getting crazy long after the switch to closed loop, but even when it is in open loop the drivers side long term fuel trims are at 160 when the passengers side long term trims are at 128( which is normal right?) the injectors are brand new and claimed to have been tested and pressure matched, but i will try and listen to each one to ensure that they are all clicking.
Just to confirm, you are saying the problem likely lies in the drivers side of the engine?

Again i really appreciate you taking your time to help me out.

AdsoYo

iTrader: (1)

The PCM is going off a separate table in open loop that doesn't use fuel trims so that 160 shouldn't be considered as an indicator of engine operating health at that point. However it is unusual to me that your driver's side pulse width is higher than the passenger side in open loop. Maybe someone else can shed some light on that one. Yes 128 is the trim value you're shooting for.

Yes I am saying the driver's side of the engine has a big problem. I'm just thinking through this here: if the car idles fine in open loop then your injectors are okay. If it idles poorly and shakes in closed loop, then maybe there's so much fuel in the combustion chamber that it can't ignite and that's where your shaking is coming from. Maybe check spark plugs on driver's side to see if they're darkened?

Your MAP increases a lot in closed loop so combustion quality went to poo. I think that's because of how much fuel is being dumped into the driver's side. I think making sure your intake and exhaust are nice and sealed on that driver's side, then checking spark plugs on the driver's side is a good start.

P.O.S. RS

Thanks for the advice! ill check that all out and see if anything improves. Again, thank you

97sswcubes

Hey guy you get your car running right?
Check for exhaust leak at the header flange.
Thats what kept me from driving my car for half a year.
Damn gasket had been burned up and was leaking slowly at first so i really couldn't hear it. The worst it got the worst the car ran Finally took the header off and replaced the gasket and wala runs perfect.
I had tried everything else in the book and nothing worked.
02 sensors were reading to much oxygen and making the car run rich as hell and causing misfire.
Hope this helps