Interesting issue on my 18 JLU with the PUG 3.6. Took it on a long road trip from WI to UT. Made it through the mountains in CO, to Moab for wheeling, then out to sand hollow to play in the dunes. No issues.
The issues started after going to the hotel in St. George, UT. Went to the hotel, parked it for a bit then ran back out (like a 15 minute drive). Got on the I-15 entrance ramp, got a blinking CEL and a "Stop/Start Unavailable Service Stop/Start System" message. The CEL went off right away. got back to the hotel and shut it down and started it back up, no issues or warnings or anything. I scanned it and it showed a P0300 and P0305. Cleared them, took it on the same route again, no issues, no codes pending or set. Just thought it was something weird maybe with it being 94 degrees and having worked it hard in the sand dunes. Drove perfectly normal.
Next day, go to leave. Got on the highway early in the morning, made it to Richfield, UT without issues. Got gas, got back on the highway and about 15 minutes after getting gas, get a blinking CEL again and the stop/start unavailable. Went completely off in a few seconds. In the middle of nowhere, so I thought as long as there wasn't a blinking CEL (or any CEL for that matter), keep going. Still driving normal. Next stop - Grand Junction. Got gas, and just as I got on the highway again, blinking CEL, then quickly turns to a solid one. Pulled over, scanned the codes, same P0300 and P0305. Cleared them and they didn't come back on, so kept going. Driving normally. Once I got into the high elevations, it seemed like it was intermittently struggling. I'm used to it in the mountains loosing some pep, but even with that in mind it just didn't seem as peppy as usual. But then sometimes it seemed perfectly fine and willing. No CEL. Made it to the east side of Denver, got gas, and again right after getting gas got a blinking CEL that then went out right away. Kept going to North Platte, NE and it's running fine. Get gas again, pulled out onto the highway and again, blinking CEL. this time it turns solid after a few seconds. Figure if its solid its not an active misfire, we only have another hour to go, so kept going. At this point, I am suspecting something purge valve related since getting gas seems to trigger it and the higher elevations and temps (in the 90s this whole time) would exacerbate the fuel vapor issues. Get off the highway in Kearney, as soon as we stop at a stop light we get a rough idle and blinking CEL, along with a very strong fuel smell. Coast into the hotel a block away and get it towed to the Jeep dealer down the street. Left a note summarizing everything above. (we continued the drive with our in-laws in their Jeep the next day).
Dealer calls, they got the same misfire codes plus a P0171 Fuel System 1/1 Lean. Also found that the t-stat housing was weeping. Had them replace the purge valve and t-stat housing, they clear the codes and say it's good to go. We drove down from WI last night and today to get it.
Got on I-80, first half hour goes fine. even got gas, no issues. About a half hour into the drive, the CEL blinks again but then goes right off. I called the dealer and told them, they said sometimes air gets into the EVAP system when it's opened and that if it doesn't come back on, that's all it was. I googled it, maybe some truth to it. IDK. Kept going since I just want to get it home. We got to Des Moines and as soon as we pull off the highway, rough idle and blinking CEL. Get gas, same thing. CEL changes to solid, and no issues the rest of the drive (no blinking CEL, always felt like it had full power). Only got a blinking CEL once after the final stop when I took it up to 4500 RPM. It seems like any large swings in RPM trigger a misfire. Keep it between 1500-4000 and it's fine. Finally made it home and got the same misfire codes.
Other notes: 119900 miles, Spark plugs are Champion/Mopar (replaced at 106k). OE coil packs still. Haven't done anything to it besides mods and fluid changes. No ticking or knocking from the engine. it's quiet throughout the RPM range. There's a jingle somewhere (sounds like a dog's collar) but its from under the drivers seat and I suspect its either something loose underneath or a skid plate making weird contact with something. No bad noises from the engine at idle or when I rev it.
Sorry for the long post. Any ideas? Thanks so much!
The issues started after going to the hotel in St. George, UT. Went to the hotel, parked it for a bit then ran back out (like a 15 minute drive). Got on the I-15 entrance ramp, got a blinking CEL and a "Stop/Start Unavailable Service Stop/Start System" message. The CEL went off right away. got back to the hotel and shut it down and started it back up, no issues or warnings or anything. I scanned it and it showed a P0300 and P0305. Cleared them, took it on the same route again, no issues, no codes pending or set. Just thought it was something weird maybe with it being 94 degrees and having worked it hard in the sand dunes. Drove perfectly normal.
Next day, go to leave. Got on the highway early in the morning, made it to Richfield, UT without issues. Got gas, got back on the highway and about 15 minutes after getting gas, get a blinking CEL again and the stop/start unavailable. Went completely off in a few seconds. In the middle of nowhere, so I thought as long as there wasn't a blinking CEL (or any CEL for that matter), keep going. Still driving normal. Next stop - Grand Junction. Got gas, and just as I got on the highway again, blinking CEL, then quickly turns to a solid one. Pulled over, scanned the codes, same P0300 and P0305. Cleared them and they didn't come back on, so kept going. Driving normally. Once I got into the high elevations, it seemed like it was intermittently struggling. I'm used to it in the mountains loosing some pep, but even with that in mind it just didn't seem as peppy as usual. But then sometimes it seemed perfectly fine and willing. No CEL. Made it to the east side of Denver, got gas, and again right after getting gas got a blinking CEL that then went out right away. Kept going to North Platte, NE and it's running fine. Get gas again, pulled out onto the highway and again, blinking CEL. this time it turns solid after a few seconds. Figure if its solid its not an active misfire, we only have another hour to go, so kept going. At this point, I am suspecting something purge valve related since getting gas seems to trigger it and the higher elevations and temps (in the 90s this whole time) would exacerbate the fuel vapor issues. Get off the highway in Kearney, as soon as we stop at a stop light we get a rough idle and blinking CEL, along with a very strong fuel smell. Coast into the hotel a block away and get it towed to the Jeep dealer down the street. Left a note summarizing everything above. (we continued the drive with our in-laws in their Jeep the next day).
Dealer calls, they got the same misfire codes plus a P0171 Fuel System 1/1 Lean. Also found that the t-stat housing was weeping. Had them replace the purge valve and t-stat housing, they clear the codes and say it's good to go. We drove down from WI last night and today to get it.
Got on I-80, first half hour goes fine. even got gas, no issues. About a half hour into the drive, the CEL blinks again but then goes right off. I called the dealer and told them, they said sometimes air gets into the EVAP system when it's opened and that if it doesn't come back on, that's all it was. I googled it, maybe some truth to it. IDK. Kept going since I just want to get it home. We got to Des Moines and as soon as we pull off the highway, rough idle and blinking CEL. Get gas, same thing. CEL changes to solid, and no issues the rest of the drive (no blinking CEL, always felt like it had full power). Only got a blinking CEL once after the final stop when I took it up to 4500 RPM. It seems like any large swings in RPM trigger a misfire. Keep it between 1500-4000 and it's fine. Finally made it home and got the same misfire codes.
Other notes: 119900 miles, Spark plugs are Champion/Mopar (replaced at 106k). OE coil packs still. Haven't done anything to it besides mods and fluid changes. No ticking or knocking from the engine. it's quiet throughout the RPM range. There's a jingle somewhere (sounds like a dog's collar) but its from under the drivers seat and I suspect its either something loose underneath or a skid plate making weird contact with something. No bad noises from the engine at idle or when I rev it.
Sorry for the long post. Any ideas? Thanks so much!
-- and before you label me a hater I own a '19 JLUR.