Advice needed with check engine light

JimNH

JimNH

JK Enthusiast
Supporting Member
Joined
Mar 24, 2020
Messages
162
Location
Nashua, NH
2008 JK 3.8 2 door.

my wife was headed home tonight from school - check engine light came on, running rough.

checked oil - low about a quart. also topped up coolant.

transmission oil level was full.

I have a JScan and plan to check for codes in the morning.

I also have plugs and wires and plan to do a tune up tomorrow...had been putting that off over the winter.

It was running really well (really well!) until this happenend. very sudden.

what else to check and report back?

JIM in NH
 
Sounds like the CEL will tell you the problem since it started when the CEL came on. If you have time now you might want to pull the codes so we can help you figure it out before tomorrow when you want to fix it.
 
OK - it's a new day. I am going to find the bluetooth sender for the JScan and try to get the codes. I will change the plugs and wires no matter what. Will shout if i need help or advice and report back what I find.
 
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OK - update

changed the plugs and wires and the drivers side heat shield - been meaning to do that anyway. Also changed the coil pack.

you would not believe how ugly the old plugs were - should post a pic. Cant believe it was running as well as it has been with those completely rusty, worn, clapped out plugs. Had they EVER been changed? Wow!

But, still running rough and stumbling, still have check engine light.

found my ODB2 scanner and used JSCAN - here are the codes now.

P0300 multiple cyl misfire detected

P0202 injector circuit malfunction - cylinder 2

P0302 cylinder 2 misfire detected

So - seems like a fuel injector problem on cylinder 2. Now to go read about how I fix that. Hope it's easy.

JIM in NH
 
Might try doing a reset, I heard that after doing parts replacements like that the ECM has to relearn.
 
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OK - but it's still running rough and I haven't done anything about the P0202 injector code. Maybe try to have them cleaned or flushed before attempting replacement?
 
not getting very far. going to have to bite the bullet and start disassembling the top of the engine to check out the injectors.

I dropped one of the old spark plugs while changing no. 3 and now I can't find it...think it's trapped between heat shield and manifold. Can't win.

I cleared the codes and am now getting the P0300, not the P0202 - weird. I am starting to think it's the wiring harness to the injectors- the insulating sleeve around the wires got brittle and fell apart, and I need to get a look at the wires further back than I can see from the throttle body sensor area. What is really stopping me is having to take off the EGR pipe - PITA.
 
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I checked the electrical connectors all over - including disconnecting the battery and then cleaning up the corroded ground for the PCM module. Getting a code for P0300, but not P0202 or P0302 now after I cleared them earlier. Reading on the interwebs, I also see that it might be a Crank Position Sensor? That is a cheap and easy change - though I hate to just throw parts at it. But I also hate to take apart the whole top of the engine/intake and then change fuel injectors if they don't really need to be changed. I might just decide to take this to the shop tomorrow - but I really kind of wanted to fix it myself if possible. Advice welcome. Even if I clear the codes using JSCAN, it still runs rough at a cold start up, and the CEL comes on after about a minute or so then starts flashing. You can look at the tensioner on the serpentine belt and see it judder like it's not running on all cylinders. If I were to take it out and drive it a bit, I am thinking that the P0302 and P0202 might come back, in which case that still points to needing to troubleshoot the injector. Wife will take my car to work tomorrow and I'll keep after this for a bit longer.

If I do end up taking it apart, I have new gaskets for the valve covers that I intended to install, so I might just tear it all apart and do that too. I also have the gasket for the upper oil pan underneath - and that is a #$%^ to do and I am putting that off. My wife gets mad when I "break" her car, but it might be broken for a few more days.
 
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Solved. When I changed the coil I crossed the wires for 1 and 5, so had constant misfire. Since i was originally chasing a misfire, I figured I just had not sorted it. Oddly, the codes for the fuel injector open circuit on cyl no. 2 went away - but i dont' know which of the things I did made that happen - cleaning up grounds, checking connectors, etc. I watched a lot of youtube this weekend! Cleared the codes this morning after having an epiphany last night about checking firing order. Ran great, wife took it to work and says it was fine. It's actually running better than before with the new plugs and wires. I WILL post a photo of the old plugs (I found the missing one when it fell out onto the driveway)...thanks to everyone who offered advice. I am just really glad that I am not pulling the engine apart this week.
 
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JimNH said:
Solved. When I changed the coil I crossed the wires for 1 and 5, so had constant misfire. Since i was originally chasing a misfire, I figured I just had not sorted it. Oddly, the codes for the fuel injector open circuit on cyl no. 2 went away - but i dont' know which of the things I did made that happen - cleaning up grounds, checking connectors, etc. I watched a lot of youtube this weekend! Cleared the codes this morning after having an epiphany last night about checking firing order. Ran great, wife took it to work and says it was fine. It's actually running better than before with the new plugs and wires. I WILL post a photo of the old plugs (I found the missing one when it fell out onto the driveway)...thanks to everyone who offered advice. I am just really glad that I am not pulling the engine apart this week.
Click to expand...


Well it's good to see your getting somewhere and sometimes it's just something you overlooked or put in the wrong place.
 
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JimNH said:
Solved. When I changed the coil I crossed the wires for 1 and 5, so had constant misfire. Since i was originally chasing a misfire, I figured I just had not sorted it. Oddly, the codes for the fuel injector open circuit on cyl no. 2 went away - but i dont' know which of the things I did made that happen - cleaning up grounds, checking connectors, etc. I watched a lot of youtube this weekend! Cleared the codes this morning after having an epiphany last night about checking firing order. Ran great, wife took it to work and says it was fine. It's actually running better than before with the new plugs and wires. I WILL post a photo of the old plugs (I found the missing one when it fell out onto the driveway)...thanks to everyone who offered advice. I am just really glad that I am not pulling the engine apart this week.
Click to expand...
Been there, done that.
 
JimNH said:
Solved. When I changed the coil I crossed the wires for 1 and 5, so had constant misfire. Since i was originally chasing a misfire, I figured I just had not sorted it. Oddly, the codes for the fuel injector open circuit on cyl no. 2 went away - but i dont' know which of the things I did made that happen - cleaning up grounds, checking connectors, etc. I watched a lot of youtube this weekend! Cleared the codes this morning after having an epiphany last night about checking firing order. Ran great, wife took it to work and says it was fine. It's actually running better than before with the new plugs and wires. I WILL post a photo of the old plugs (I found the missing one when it fell out onto the driveway)...thanks to everyone who offered advice. I am just really glad that I am not pulling the engine apart this week.
Click to expand...
Reminds me when we were rebuilding my 1955 Willys, we had the the distributor 180 degrees off and couldn’t get it fired up. Took us a while scratching our heads before it dawned on us.
 
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Here is a pic of the spark plugs I took out. Ugh. I checked the car again today when my wife got home - no codes! The single plug is about the best one.

IMG_4602.jpg



IMG_4601.jpg
 
You got your moneys worth out of them but lost it in the reduced gas mileage. Did you happen to put anti-seize on the threads of the new ones?
 
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Yes, I did put anti seize on the new plugs. I used the Bosch double platinum plugs. I have read that you are not supposed to add anti-sieze if the OEM doesn't call for it, as it changes the toque value, but I always do it as it beats the alternative. I did use a torque wrench to reinstall them, and my natural inclination would have been to make them much tighter than that. Also, I think it's hard to get a good torque wrench reading when you have to use a universal joint to reach the socket extension into alignment. Even though they were horrible, they were all tan and not showing evidence of the engine being either too rich or too lean, so that is a bonus. No. 5 showed a little oil on it, but not so much that is is worrying me. I should have done a compression check on all cylinders while I was at it. If it were easier to reach the plugs that would help, but I should definitely do it next time I have a reason to be in there.
 
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I probably wouldn't on most plugs but as long as the threads are on these plugs and I noticed yours were rusty looking it could maybe cause a problem removing them next time.
 
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THE SAGA CONTINUES. A couple of times this week the engine would misfire - only a warm start - and the code is now ONLY p0202 - no. 2 cylinder fuel injector circuit. I am going to go to NAPA and buy one injector and one plug, and then tear the top off of the 3.8L engine. I promise pics and to let you know what I find.
 
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