Performance Issue

[shadycamaro]

I've been chasing down an issue that I just can't seem to pinpoint... hoping maybe some one else has experienced or has a fresh idea 💡

Car runs great when it wants to. Experiences an intermittent issue (that is progressing in frequency)... where powerband is lost, slight bucking/possible misfire, deceleration backfiring/exhaust popping, and overall sounds like trash (loud drone at cruising). Almost sounds as if the mufflers just fell off at rear.

I've replaced the spark plugs, the wires, Evaporative Purge Solenoid Valve, sprayed the MAF sensor, cleaned/reoiled the CAI filter. My tuner says not worth investigating/replacing coil packs (as they rarely go bad). Contemplating front O2 sensors (cats are deleted), but again was told if it were them it would not experience the issue WOT (which it does; won't pull hard during issue).

Car has approx 76k, LT headers, CAI, and cammed. Rockers and valve springs checked out good. Only other noticeable issue while performance is lacking is with AC off it sounds like the blower motor is on but is not and feel no air from vents. The car doesn't usually rattle interior wise, but when this occurs it will cause some plastic pieces to (from the loud exhaust vibration).

Used to run great when 1st started and only happened when I stopped shortly after and restarted the car (ie. Gas station, quick store run, etc). Now noticing it happening while driving, will run well, get loud and bogged, then go back to running well.


Any thoughts??? Much appreciated 🙏

[1JEWLDSSRS]

No CEL, no codes??

[shadycamaro]

Originally Posted by 1JEWLDSSRS

No CEL, no codes??

Showed P0430 (perm) and P2099 (perm)... Catalyst System Low Efficiency Bank 2 and Post Catalyst Fuel Trim System High Limit Bank 2.

Chalked this up to the CATs being deleted, but also figured that the tune should have them shutoff (downstreams)... but that's all that was showing.

Car has never displayed CEL during any of the issues experianced.

[ZL1_Chris]

No service stabletrack? Just a thought, how old is your battery? Possible ground issue. Possible crankshaft or cam sensor but there'd be DTCs to read unless they've been turned off.

[shadycamaro]

Originally Posted by ZL1_Chris

No service stabletrack? Just a thought, how old is your battery? Possible ground issue. Possible crankshaft or cam sensor but there'd be DTCs to read unless they've been turned off.

Didn't appear to be cleared/erased... everything at top was solid green. I'm gonna drop it Thursday at the shop for him to diagnose, was just hoping to not shell 160+ an hour 😒

I'm not scared of turning a wrench or tearing something apart, but nothing is showing its ugly face to be fixed.

[Tmcgee2010]

sounds exactly like what mine does when it goes into limp mode on a hot start. these usually happens if it takes too long to crank and it causes the symtoms your having but usally my rpm gauge stays off as well. i recently added the 2nd ground cable from the trans to frame and it seems to have helped alittle but im thinking the battery has some age on it now and is on its way out

[shadycamaro]

Originally Posted by Tmcgee2010

sounds exactly like what mine does when it goes into limp mode on a hot start. these usually happens if it takes too long to crank and it causes the symtoms your having but usally my rpm gauge stays off as well. i recently added the 2nd ground cable from the trans to frame and it seems to have helped alittle but im thinking the battery has some age on it now and is on its way out

Thabks for the suggestion!

I just bought a set of additional ground cables from a forum member selling them... hopefully that helps out. Will look into replacing the battery as well, I'm sure it's older.