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2021 Trackhawk P0300 Help

1897 Views 5 Replies 4 Participants Last post by  Leophay
Hello all! Joining some of the forums outside of Facebook seeking some additional help. I'll provide a link to that post as well as it's a bit lengthy, I'll keep it short(er) here.

I'm getting a rough idle accompanied with a P0300 code. Jeep drives fine but obviously want to resolve the issue and not risk long term damage.

My rig: 2021 Trackhawk, ordered June of '21 and took delivery in September. Currently at 5478 miles. Modifications include a GT Haus cat back exhaust (installed at ~1500 miles), Legmaker intake (installed at ~2500 miles, Billet Technology catch can (installed ~50 miles), and Ravelco anti theft unit (installed at ~150 miles). PCM is unmodified on the stock tune. Always fueled with 93 at a Sunoco or other top tier station, and always watch them press the button due to some mild OCD and paranoia.

Timeline of Events:
5/24CEL first appeared after making a couple stops at stores on the way home from work. Before light appeared, I had notice a bit of a rough idle to the point where the truck sounded like it was cammed. After CEL, truck driven home at highway speeds, no harsh acceleration of aggressive driving. Catch Can removed per FB recommendation related to possible vacuum leak.
5/25Called dealer to schedule appointment for CEL Diagnosis and oil change.
5/26Dealer dropped off prior to opening for service. Dealer called mid morning and first impression was a PCM issue. Did inquire about the aftermarket exhaust and requested remote to close/open muffler valves. Wife dropped off remote during lunch break. Dealer also questioned aftermarket "alarm" system. Explanation provide for the functionality of Ravelco.
5/27Dealer had advised no change in misfire with exhaust valves open or closed. Commented that the misfire only occurs while idling and not tied to a specific cylinder.
5/28Vehicle collected from dealer for long weekend after advised that there appears to be no risk of catastrophic failure.
5/29 - 5/3010 gallons of new fuel from different station added to the roughly 1/4 tank still in vehicle. CEL did not appear but rough idle still noted. Additional code for C0572 also appeared at this time. Vehicle parked for weekend and was not driven.
5/31Vehicle was returned to the dealer at opening for further diagnosis. Loaner vehicle requested if vehicle was going to be at dealer for additional time.
6/1 - 6/6Dealer continued diagnosis and system testing. Complete list of tests not provided but was noted that fuel quality had been tested and passed.
6/6Dealer advised that loaner vehicle was not available and root cause for misfire not identified. C0572 code still present advised to be related to unplugging of harnesses during diagnosis. Was advised to drive and monitor. Post collection, vehicle filled with full tank of 93 fuel and bottle of Techtron Fuel System cleaner.
6/7 - 6/10Vehicle driven without incident totaling ~150 miles. CEL remained off but code for C0572 persisted
6/11Battery unplugged in an attempt to clear C0572 code. Reconnected battery and drove vehicle for weekend errands in the area. After visiting a local Lowes nearby to the dealer, I stopped in to update on condition. Advised service agent that CEL had not reappeared all week and attributed the CEL to possible bad gas. As vehicle was exited the dealer, CEL re-appeared. Updated service agent and was told to drop off on Monday.
6/12After market air intake removed and replaced with OEM unit. Battery again disconnected to clear codes and reset parameters. CEL reappeared and issue persisted.
6/13Vehicle was returned to the dealer at opening for further diagnosis. Loaner vehicle was again requested if vehicle was going to be at dealer for additional time.
6/14STAR ticket opened stating CEL and rough idle. Star responds to check exhaust timing then proceed to smoke test through brake booster hose and introduce propane through IAT sensor opening while running.
6/15Dealer updates misfire persists and timing at 0.4 degrees retarded. STAR advised to check purge valve and run compression test while vehicle running, then to check airflow through exhaust at TDC. Dealer advised that attempted cam phaser cleaning. Vaccuum needle from equipment fluctuates but tech questions 12 year old gaugef.
6/20Dealer updates that exhaust phaser cleaned, scoped cylinder and found no signs of damage. no leak down found on Cylinders 6,7 or 1,2. New vacuum gauge validates 15-17 hg with no fluctuation. STAR recommends cooling system check. Dealer advises no overheating issue, none of the plugs or pistons look "clean" and still misfires in P or N but not in D or R, normal and aggressive driving. Dealer inquires about catalytic converter restriction. STAR recommends reinstalling factory exhaust and re-evaluate concern. Service manager called and advised that likely culprit is the aftermarket exhaust. Vehicle was picked up same day and I swapped the exhaust to the factory unit in home garage. Battery disconnected during installation. Upon completion ~20 start/stop cycles before CEL reappeared.
6/21Vehicle returned at opening and again requested loaner vehicle.
6/21 -6/25Vehicle sat without further diagnosis - No STAR response
6/25Loaner vehicle granted and collected from dealership
6/27 -7/4Vehicle sat without further diagnosis - No STAR response
7/5Dealer advised that additional testing performed to check Air/Fuel condition which appears normal. Star case advised to be commented on and will be re-opened. Internal recommendation from another tech to remove valve covers to investigate any sort of mechanical failure.

List of possible areas to investigate I've given dealer (I'm sure I'm forgetting some as it was a last minute handwritten note):

Sending Unit/Fuel Pump
Spark Plugs
Vacuum Leak
Throttle Body
Coil Packs
Valve Seal
Leaking Intercooler
Bent Valve
Valve Seal

Link to FB post: Facebook Forum Posting

Trying to see if anyone has had a similar issue or possible additional areas to try. I don't want to go lemon law route. At this point I just want the Jeep fixed. Thanks in advance for the assistance!

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Has STAR sent anyone out? After a certain point they would usually send someone out IIRC
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