Flashing check engine light

Rusty Rivets

Rusty Rivets

Member
Joined
Mar 12, 2019
Messages
27
Location
West Tennessee
I have a 2002 TJ Sport that I've had for about 5,000 miles and it’s been running rougher since I got it. Odometer currently reads 133,000. I have a misfire in cylinder one only and at times it’s rougher than other times. From what I read, the flashing cel indicates that raw fuel is being burnt in the cat and I do believe for sure that’s what is happening as I ran my Jeep for approx 15 minutes and crawled underneath to find the bottom part of cat glowing from so much heat.

The glow spot was approx 3-4 inches in diameter. My number one cylinder must have more fuel that what it can burn I assume? Seems logical to me since the fuel is heating up the cat and sometimes had string smells. For how long has yours been running good and what was your final conclusion of the cure? I’ve read these forum links until my brain can explode and have learned a much better insight to how things work. @Jerry Bransford has posted numerous times on this issue and definitely seems to be a very knowledgeable person, I just wish I knew of a more clear cut solution. If anybody could reply I’d be most grateful.
 
What does your #1 spark plug look like? Does it run better when cold in the morning and then start running rougher only after it starts warming up?
 
You can order a $10 and up Bluetooth or wifi OBD2 scanner adaptor from Amazon/eBay and then download Torque lite or Auto Doctor for free and they will show trouble codes, freeze frames and very importantly fuel trims levels, O2 voltages and so on.....
 
Last edited:
  • Like
Reactions: Rusty Rivets and jjvw
Yes like Jerry said, check the #1 plug, if it looks dark and sooty you may have a rich condition caused by a bad 02 sensor or possibly a bad #1 fuel injector.
With 133k I would pull and examine all the plugs to help in your troubleshooting and go from there
 
Jerry Bransford said:
What does your #1 spark plug look like? Does it run better when cold in the morning and then start running rougher only after it starts warming up?
Click to expand...
Pics posted of number 1 spark plug Jerry Bransford. I put new plugs in about a year and a half ago. I changed all six plugs again today and they were all approx the same condition as pics posted. It actually had been running worse in cooler weather this week. Kinda better after warmup in my opinion but misfire lessens or intensifies without rhyme or reason. Also I’d like to say thank you for your reply, I have learned so much from reading material that you post and am very grateful.

5E8D7E0B-630D-4C35-AAA5-2ACBF4C1F11B.jpeg


7B425623-0472-4C30-B7D7-5DC1A7735EAB.jpeg


4F299BF9-C968-448A-BD85-54CE7FAE7CBE.jpeg
 
KCsTJ said:
Yes like Jerry said, check the #1 plug, if it looks dark and sooty you may have a rich condition caused by a bad 02 sensor or possibly a bad #1 fuel injector.
With 133k I would pull and examine all the plugs to help in your troubleshooting and go from there
Click to expand...
I posted pics of spark plug, in my opinion it doesn’t look like it’s been in a rich environment. What about you?
 
twistedlv said:
Is your CEL currently on? If so, cycle your key from Off to On three times. On the third time is should show you any codes on the odometer.
Click to expand...
It was on until I unplugged battery this morning while replacing plugs. I hooked battery back up, started engine and it was gone. I’m almost certain it will pop up again and when it does I will try what you said. The only code that I got from it when it had been scanned was the misfire on cylinder one. It seems to be a common occurrence from what I’ve read with these jeeps which makes me wonder..... is the 4.0 really that great of a engine or am I just having bad luck with this one?
 
Is P0301 the code you are getting? That would be misfire on cylinder number one. But the part that is confusing me is the glowing cat, as the PCM will shut down the injector on any misfiring cylinder.
I wonder if you have a bad cat?
 
  • Like
Reactions: Rusty Rivets
twistedlv said:
Is P0301 the code you are getting? That would be misfire on cylinder number one. But the part that is confusing me is the glowing cat, as the PCM will shut down the injector on any misfiring cylinder.
I wonder if you have a bad cat?
Click to expand...
Yes sir that is the code I’m getting. I completely agree about the cat, I suppose it could be a bad cat? What would be the cause to make it go bad though? Is the bad cat what’s making my engine misfire? Or....... has whatever is making my engine misfire caused the cat to go bad I. The process? If I knew exactly what to fix and could solve the issue I sure would but troubleshooting this issue has really challenged me bud.
 
I'm just spit balling about the cat. It may or may not be related to the misfire, it's just the first time I have heard anyone mention those symptoms together. I feel your pain though. I've been chasing an intermittent P0301 for a while now. Have you downloaded a FSM yet?
https://wranglertjforum.com/attachments/2002-tj-service-manual-pdf.14039/

But yeah, misfires are a bitch to isolate because anything that affects the speed of the crankshaft can cause a CEL. Could be a sticky idler pulley, or a sticky valve, or anything in between.
 
twistedlv said:
I'm just spit balling about the cat. It may or may not be related to the misfire, it's just the first time I have heard anyone mention those symptoms together. I feel your pain though. I've been chasing an intermittent P0301 for a while now. Have you downloaded a FSM yet?
https://wranglertjforum.com/attachments/2002-tj-service-manual-pdf.14039/
Click to expand...
Well next time your misfire starts acting up and if you can, get underneath and check your cat above the transmission skid plate. You can see through a hole in the skid plate. That’s where mine glows. I wonder if yours is doing it too? I haven’t downloaded that. What is it?
 
Rusty Rivets said:
Pics posted of number 1 spark plug Jerry Bransford. I put new plugs in about a year and a half ago. I changed all six plugs again today and they were all approx the same condition as pics posted. It actually had been running worse in cooler weather this week. Kinda better after warmup in my opinion but misfire lessens or intensifies without rhyme or reason. Also I’d like to say thank you for your reply, I have learned so much from reading material that you post and am very grateful.

View attachment 81944

View attachment 81945

View attachment 81946
Click to expand...
Those plugs look ok, maybe a bit on the lean side. I would get an engine code next.
 
  • Like
Reactions: Rusty Rivets
Top Bottom
Back