I'll try to be as thorough and as short-winded as possible-

Car: '02 Camaro SS, 50k miles, stock LS1, Am Racing long tubes with catted y into intermediate pipe, MagnaFlow catback, dual exit, tune.
Car driven rarely, parked for a couple months over winter with fuel stabilizer.

Drove car a couple times in the spring, ran fine. In May, got the car out to have the tune updated, changed from SD tune back to MAF, and for dyno # curiosity. I was on the SD street tune for about 4 yrs, zero problems. The day prior to the scheduled tune, I changed the oil on the car and cleaned the MAF (CRC MAF cleaner). The MAF never came out of the car, just unplugged.
Irridium plugs/MSD wires were done concurrently with headers and orig SD tune in 2009, but no more than 5k miles on them, so left them.

Upon starting the car to LEAVE for the tune (still SD, MAF still unplugged), there were a couple very subtle pops out of the exhaust...I didn't think much of it, topped off with some 93, and drove about 30 miles for the tune appt. As the car was dyno'd, it continued to occasionally pop at idle and idle a little rough. Everything on HP Tuners looked good per the tuner...attributed to old gas. Car made 360/370 on the dynojet...tuner said similar cars are typically 350-360 on his dyno.

In route home from the tune, I get an SES light...P1153, B2S1 insuff switching. Figured this is the source of my troubles. Ordered new O2s for both fronts. Rears have been tuned out since first tune. For the hell of it, cleared the code and took it for a drive a couple weeks later before swapping O2s....set 0133 (b1S1), 1153 again, and 0161 (B2S2, wtf!?!). Idle becoming worse, exhaust pops louder.

Replaced both O2s (previous Delcos, replaced with NTKs). Checked thoroughly for exhaust leaks. Cleared codes, drove. Set 0153, 0133 (both fronts slow response) and now 0300 (random misfire). This more and more sounds like bad gas. Still shitty idle, car still pulling good in higher rpm range.

Decided to go for a long trip tomorrow to assure I had all fresh gas in it, and then was going to change the fuel filter. I drive out to my shop tonight to park my truck and get the Camaro, and while idleing as I locked up, it throws 0300 FLASHING (no other codes). On previous occasions, it took 15-20min of driving to set any DTCs. I went ahead and drove the car about 2 miles to see how it acted and went back to the shop...now more of a backfire than a pop, and was now noticeable at high rpms (0300 came back flashing after clearing, no others).

Diagnostics: Driver side cat around 500 degrees, passenger cat around 350. Tried to check primary temps, but tough to measure at the same distance at the same spot on the primary...temps veried as much as 50 degrees with no pattern. When feeling the exhaust at the tips, the driver side tip is emitting more flow and hotter exhaust than the passenger side (50 degrees difference).

Thoughts: Obstruction somewhere in the exhaust? If it's a cat, why is the exhaust flow out the tips different? If it's in the muffler, why is one cat hotter than the other? Why the O2 involvement? My shop is rodent free as far as I know, but I suppose mice could have made a nest somewhere. I plan to pull the front O2s to see if that smoothes up the idle to eliminate the above thought.

I know I'm going to probably need to hook up to a better diagnostic tool to pinpoint the issue, but I thought I would see if this series of events stands out to anyone as something obvious before calling the tuner. And I know the O2s codes are freq with longtubes, but I've gone 4 yrs with these headers and never have had that issue. Any help/theories are GREATLY appreciated...I'm anxious to figure this out. Thanks!

 

I just fixed my exhaust pops. Plugs and wires were at fault. I didn't have any SES and my O2's were switching fine. AFR's were good but there was unburnt fuel in the exhaust. I suggest you revisit the plugs/wires.

 

Thanks, definitely in my plans to check. The way the problem has progressively gotten worse makes me think it has to be something bigger tho. I'm just going nuts because I'm out of town and can't work on figuring this out.

 

Mine got progressively worse as well.

 

Any other thoughts/suggestions to troubleshoot? Get back in town tomorrow and have a few hours to attempt diagnosis. Thanks

 

Do you have a way to monitor O2 sensor voltages? STFT's and LTFT's?

Be good data to see.

I have a Bluetooth OBDII module and an app for my android and it works great.

 

Don't believe my scan tool does that. What would that tell me? I did replace both sensors and traced the wiring to make sure nothing was damaged

 

To see if either or both banks is running lean and causing the comp to dump fuel at it causing your exhaust pops. Looking for balanced STFT's side to side and low numbers, same for LTFT's.

 

Freeze frame data from when the last random misfire code set...not sure if this helps...

Fuel sys 1 CL
FS 2 CL
Calc load %3.5
ECT (F) 192
STFT B1 5.4
LTFT B1 0
STFT B2 3.1
LTFT B2 0
MAP 10.6
RPM 905
Speed 7mph
MAF (lb/min) 1.309
TPS% 0

I cleared the DTC and started it back up...when freeze frame after that showed STFT and LTFT for both banks as 0.

 

Had a minute to pull plugs this morning...cylinders 5 and 7 were fouled. MSD wires all tested around 25 ohms. Any more thoughts? Gonna pull the valve cover while the coils are off and take a look.

 

Springs looked fine. Replaced 2 plugs, swapped coils 1 and 3 with 5 and 7 to see if the cylinders changed. Car ran much better until it went to closed loop, then same thing again. Pulled out B1 plugs again, but no evidence of fuel...hard to read the new plugs though with that little time. I'll try to get to bank 2 today to see what it looks like.

 

Plugs and wires all good on bank 2. Springs, rockers, pushrods fine. Have a friend of a friend bringing out a Tech2 in a week to see if the misfires are still in 5&7 and to isolate how often the misfires are happening and if one cylinder is more prevalent.