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CEL Flashing When Driving Uphill

4K views 21 replies 7 participants last post by  mntnbnjo 
#1 ·
Changed the oil for the first time in a WJ I recently purchased. I live on a large hill with a very slanted driveway. I used a fluid transfer pump (have used in the past with other cars for oil changes and no problems) to pump the oil out via the dipstick tube and when no more oil came out I removed the drain plug and pumped what remained from the pan. I refilled with 5 quarts 10W30 and a bottle of Rislone Engine Treatment concentrate (16.9 fl oz). I pumped the old oil out into a 2 gallon jug and removed a hair over 5 quarts. I assumed with the capacity being 6 quarts that refilling with 5 quarts and then half a quart of Rislone Engine Treatment would probably put me at about 6 with an residual oil that didn't pump/drain out.

Drove it down the hill to a flat parking lot and the oil pressure was around it's usual mark. I checked the oil level and the oil level was about half an inch above the max level after idling about two minutes. I drove it back up my hill and noticed a loss of power and the check engine light began flashing. I pulled into my driveway and turned the engine off and let it sit a minute and started the engine back up and it flashed again. I turned it off and checked for a code but it didn't produce any. I turned the engine back on and let it idle for about five minutes and the light didn't flash. I've never had a CEL come on nor flash before so wasn't sure if this was normal for a WJ after a change.. maybe the oil hadn't circulated enough to build up enough pressure before I drove up the hill? Read that a flashing light can sometime be a cat issue, could the Rislone engine treatment be causing a catalytic converter issue?
 
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#3 ·
5.5 quarts in your crank case is fine but if you're seeing your level a half an inch above the max level, you have way too much oil in your engine.

A flashing CEL likely means you're misfiring, which would also explain why you felt a loss of power.

Edit: Missed your second post. A half a CM is not near as big of a deal as a half an inch!
 
#5 ·
mntnbnjo said:
Took it for a five mile drive and up and down several hills and power is back to normal, cel didn't come on and checked the oil level again and it's in the middle of safe. Not sure what happened. Sent from my iPhone using Tapatalk
you never mentioned replacing the oil filter in all that other detail. Flashing engine light is a misfire. It's interesting you did the key dance to check codes and all it said was done.
 
#7 ·
Ya know, that reminds me...

YEARS ago when I first bought the WJ, a lifter wiped out a cam lobe and started misfiring badly. I successfully replaced what was needed and off I went. Granted, I was then very sensitive to any "hiccup" and thought I felt them every now and then. Not too long after, it would randomly do just what you described - misfire, run rough, flash the CEL. I'd turn it off then turn it back on and all would be well. I was paranoid it was a lifter/cam issue but it eventually stopped the odd behavior. It happened to my wife multiple times as well. She would call worried and I'd tell her to pull over, turn it off then on, and she'd be good to go. I don't think it ever stored a code either.

Quite a while later, my crankshaft position sensor went out. Was that the cause? Perhaps, but I'd only be guessing.

Another possibility - perhaps you had a bit of injector heat soak causing your misfire and by letting it cool off, it resolved the issue on its own.

Just throwing out ideas.

:tea:
 
#11 ·
Had similar issue recently. Passing on the highway in heavy rain, engine went weak, laid the pedal down to WOT, power became intermittent and jolting. Pulled over, shut her down, got codes for misfire. Fired back up, never did it again. Codes went away. I thought it may have been a bad coil, so I carried a spare one around for a few days just in case. Not sure if rain had anything to do with it. Ended up just taking the coil back to the store before return period was up.

Old jeep with random electrical issues, probably "normal", or at least expected on some level. At least for me, not the first time something odd happened and simply cured itself.
 
#12 ·
Just yesterday, in a non-Jeep vehicle, I pulled up to park and the truck was running quite rough. My wife asked if I felt it. I told her that I could and that it was misfiring but with no light on the dash, if I turn it off and back on, it would run perfectly fine. Sure enough, that's exactly how it worked out.

Why vehicles do this from time to time, I haven't a clue. I figure they're angry about something and acting out.
 
#14 ·
While driving to work yesterday morning my CEL came on again. This time it came on about three minutes into my drive while getting on the interstate. It flashed for a bit then went solid and then flashed a while longer before going solid. This time I got a few codes: P300, P302, P303, P305. I cleared the code once I got to work and it didn't return on my trip out for lunch, home, to the store or back home.

I made a quick trip out this morning at 6 AM and all was fine. Went back out around 2 today and the CEL returned. This time a P305 code. Cleared the code and no recurrence since on a few trips.

Prior to the oil change, I had driven about 1,000 miles since purchasing the vehicle. There is/was a bit of rough idle but not excessive.

Could the Rislone engine treatment I used be the cause. Wondering if there's a chance that the engine treatment broke up some sludge that is clogging the fuel injectors.

These last two times with the CEL I didn't notice any sluggishness or performance issues. Will driving with a misfire cause any damage until I figure out the cause?
 
#15 ·
#16 ·
Week ignition coil under a heavy load will fail to spark the gap and produce a missfire

Watch your fuel pressure, or pull your injectors and do the home reverse flush or just get a replacement set. It's a start. I don't know what the video is about but repeated driving with the missfire will melt your cat and or gas your oil wiping a main or rod bearing.
 
#19 ·
Thanks! I've ordered new coils and injectors. I'll be replacing them next weekend hopefully when I replace the leaking valve cover gasket.

Sent from my iPhone using Tapatalk
I'm curious to see if the new injectors and coil will fix your misfiring. Good Luck
 
#21 ·
I agree. Doing one at a time means you can find the actual cause to the problem.
 
#22 ·
I checked the fuel pressure and there were no issues. I replaced the coil pack yesterday evening and put about 75 miles in since and the CEL hasn't returned. Before replacing the coils, the misfires were almost predictable on my route to work and back home so I'm fairly confident that this was my issue. Thanks everyone for the help!
 
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