3.8 Engine Troubles ? Help Please!

madstiles

madstiles

New member
So I have a 08 JKU manual trans that has me baffled. On good days it runs like it should. On iffy days after it warms up it idles fine when you take off it is lacking power but doesn't seem to be misfiring as you get above 2500 rpms it cant hesitate at times around 3000 rpms it can rattle? a bit. Sometimes if i stop and shut it off, wait a minute and restart it will run normal again for a bit, sometimes that doesn't work. it only happens after the engine is warmed up which it seems to warm up really quick. if i run 87 octane gas it is worse so i run premium all the time. Their is no check engine light on . Any help would be greatly appreciated. If you need more info please ask. I am baffled beyond belief at this point and have no clue what is wrong lol Thanks in advance !!
 
madstiles

madstiles

New member
It has 80000 miles. I changed plugs wires and pcv valve about 1 year ago. Have not replaced any coils injectors or the belt.
 
TRLJNKY

TRLJNKY

New member
Very well could be fuel delivery also. If you have means to run a fuel pressure test Id do that just to rule out a fuel pump issue. Thats free (if you fo it yourself) May be even able to get the tool for free from auto parts store.
 
Judesign

Judesign

Caught the Bug
It's just weird to be acting like that but not throwing a code. Maybe have the auto parts store run a check just to be sure
 
madstiles

madstiles

New member
Judesign said:
It's just weird to be acting like that but not throwing a code. Maybe have the auto parts store run a check just to be sure
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That's the part that gets me! If it was a sensor or cat or misfire it should have a code I would think. When u turn the key on the light works I thought it might be burnt out lol
 
madstiles

madstiles

New member
Well I have yet to take the Jeep to a shop for any repairs and I have finally gave in :-( I am definitely at a loss on this one gonna let some pro's figure it out for me before I waste anymore money on parts that don't fix it lol I'll post their findings hopefully tomorrow. Thanks for the help!
 
JeepinLife

JeepinLife

Caught the Bug
madstiles said:
Well I have yet to take the Jeep to a shop for any repairs and I have finally gave in :-( I am definitely at a loss on this one gonna let some pro's figure it out for me before I waste anymore money on parts that don't fix it lol I'll post their findings hopefully tomorrow. Thanks for the help!
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What all have you tried to diagnose? Hate that you had to fire the parts cannon at it.
 
madstiles

madstiles

New member
Well shop told me plugs were bad but I just changed them couple months ago they almost looked melted. They said that because I run high octane it could cause it or the engine is working to hard because I haven't regeared.. I think he doesn't have a clue so he's just guessing or hell I may be wrong.
Is it possible the previous owner has a tune in it and it's messing up?
 
WJCO

WJCO

Meme King
If higher octane fuel makes it run better, it is probably some kind of abnormal combustion. I myself would try an injector cleaner and decarbonize the intake just to eliminate that. If it is the same cylinder misfiring repeatedly then you would have a code. BG 44K is a good product to clean some stuff out.
 
madstiles

madstiles

New member
WJCO said:
If higher octane fuel makes it run better, it is probably some kind of abnormal combustion. I myself would try an injector cleaner and decarbonize the intake just to eliminate that. If it is the same cylinder misfiring repeatedly then you would have a code. BG 44K is a good product to clean some stuff out.
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I've done the sea foam twice once through the booster line once the spray kind through air intake also in the has a few times last time sea foamed no smoke came out so I assume it's clean I'll try the bg44 next time though thanks for the help :)
 
ScoobyCarolanNC

ScoobyCarolanNC

Active Member
I'm calling bullshit on the high octane thing. Have your dealer flash the ECU & put new plugs in. Your tuner theory might hold water. Those things are fuckin dumb.
 
WJCO

WJCO

Meme King
madstiles said:
I've done the sea foam twice once through the booster line once the spray kind through air intake also in the has a few times last time sea foamed no smoke came out so I assume it's clean I'll try the bg44 next time though thanks for the help :)
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If there was an issue thee, that should have resolved it already.

ScoobyCarolanNC said:
I'm calling bullshit on the high octane thing. Have your dealer flash the ECU & put new plugs in. Your tuner theory might hold water. Those things are fuckin dumb.
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^There might be something to this. Especially with it being intermittent.
 
TRLJNKY

TRLJNKY

New member
All I run is high octane in mine at 150k. Anything less and I get detonation. No tuner just intake and exhaust, 315's, and 4:10. Oh I climb hills all the time around me so under a lot of load. Pisses me off actually lol. Ive seafoamed it and put Lucas injector cleaner through it every oil change. Moral of the story is mine only eats high octane 91 and plugs are fine. Can only speak from my experience though. Hope your issue gets resolved.
 
jeeeep

jeeeep

Hooked
madstiles said:
Well shop told me plugs were bad but I just changed them couple months ago they almost looked melted. They said that because I run high octane it could cause it or the engine is working to hard because I haven't regeared.. I think he doesn't have a clue so he's just guessing or hell I may be wrong.
Is it possible the previous owner has a tune in it and it's messing up?
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did you replace the plugs with the stock plugs heat range, gap them properly and use dielectric grease?

I've tried the V and tri-fork tip plugs and they made my jeep run worse the E3 was the worse of the bunch I've tried. I've have good luck with Autolite and Champion

I run a Demon Coil on my 2010 3.8 with stock plugs gapped for the coil and run premium, have since 6 months new no issues. I have a tune on it to change the timing and run 93 octane.

if your plugs aren't the proper heat range or gapped properly I can see them burning up prematurely with a higher octane fuel since it holds the combustion longer. If you have the bad plugs I'd check the heat range on them, sounds like the heat range was too low on at least the ones that look melted. I'd also check the gap.

I'm calling bullshit on the regearing comment, the engine does work harder but it's not going to melt plugs lol, I know too many guys that run larger tires and high octane fuel no issues.
 
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madstiles

madstiles

New member
ScoobyCarolanNC said:
I'm calling bullshit on the high octane thing. Have your dealer flash the ECU & put new plugs in. Your tuner theory might hold water. Those things are fuckin dumb.
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I didn't know they could reflash I'll have to give them a call once this hurricane passes lol
 
madstiles

madstiles

New member
jeeeep said:
did you replace the plugs with the stock plugs heat range, gap them properly and use dielectric grease?

I've tried the V and tri-fork tip plugs and they made my jeep run worse the E3 was the worse of the bunch I've tried. I've have good luck with Autolite and Champion

I run a Demon Coil on my 2010 3.8 with stock plugs gapped for the coil and run premium, have since 6 months new no issues. I have a tune on it to change the timing and run 93 octane.

if your plugs aren't the proper heat range or gapped properly I can see them burning up prematurely with a higher octane fuel since it holds the combustion longer. If you have the bad plugs I'd check the heat range on them, sounds like the heat range was too low on at least the ones that look melted. I'd also check the gap.

I'm calling bullshit on the regearing comment, the engine does work harder but it's not going to melt plugs lol, I know too many guys that run larger tires and high octane fuel no issues.
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Yes sir I used the factory plugs and checked gap didn't need to adjust as they preset also used the grease stuff.
I was thinking of buying a tuner to see if that helps but think I'm gonna call and see if they can reflash as was suggested before anything else.
What kind of tuner do you use?

Their comment about regearing kinda helped me justify gears with the wife though lmao

It is running better now but still not full power it comes and goes which is what gets me especially since it doesn't throw a code . Pretty sure they think I'm crazy lol
 
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