Cadillac STS The newest installation of the performance sedan from Cadillac, having replaced the Seville

05 STS V8 Misfire

  #1  
Old 04-19-2016, 12:11 AM
Tomcat_AL200's Avatar
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Location: Montclair, VA
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Default 05 STS V8 Misfire [Solved]

Good evening all,
I have a 05 STS with the Northstar with 115k on it that has been nothing but a pleasure since I bought it last year. Friday the car started idling rough out of no where while my wife was driving, only noticeable at stop lights, but it threw multiple codes:

P0174 Bank 2 Too Lean
P0446 Evap Emission Sys Vent Control (Preexisting code)
P1101 Intake Air Flow System Performance
P0068 MAP/MAF - Throttle Position Correlation
P0302 Cylinder 2 Misfire detected
P0171 System Too Lean Bank 1
P0420 Catalyst System Efficiency Below Threshold
P0300 Cadillac FSC DTC Random Misfire Detected

Going off of what some other people have expierenced, I changed the spark plugs to OEM (completely wrong ones were installed), replaced the throttle body gasket, and re-torqued the Intake Manifold bolts to torque in proper sequence. Unfortunately, once I fired it up, there was still excess vibration, albeit it a hair smoother. A short test drive gave me the following codes:

P0302 Cylinder 2 Misfire detected
P0446 Evap Emission Sys Vent Control (Preexisting code)
P1101 Intake Air Flow System Performance
P0068 MAP/MAF - Throttle Position Correlation
P0300 Random Misfire Detected

So, what do you all recommend for my next step? Could it be the MAF? It looked clean and I was hesitant to spray it down. Since the misfire is primarily highlighting Cyl 2, might it be the coil? I'd appreciate any help as I have a 1 hr commute to base as it is and dropping my wife off at work and picking her up is really not making that commute any shorter.
 

Last edited by Tomcat_AL200; 04-19-2016 at 11:34 PM.
  #2  
Old 04-19-2016, 11:28 PM
Tomcat_AL200's Avatar
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Location: Montclair, VA
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Well gents, replacing the bank 2 Coil pack seems to have done the trick! I swapped the suspected bad #2 Coil to the #1 cyl and boy did the car run like **** but, all the bank2 Codes transferred over to bank 1 and the misfire code for cyl 1. After that I cleared the Codes, put the good ignition module on Cyl 1, installed the new bank 2 ignition module by disassembling it so that I could get it in around the refrigerant(?) lines. Hell, it took me longer to do an oil change (another story), than to swap the modules.

Thank you all for your help in getting our beloved "Vera" back on the road!
 
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