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What did I break?

8K views 62 replies 21 participants last post by  BJB 
#1 ·
My Jeep:
2007 with magnacharger and some exhaust work, stock otherwise.

My Problem:
Was driving down the highway and decided to go to the top of 4th gear (~140mph) and when I got close to red line, acceleration stopped (kind of like it had a governor and the fuel shut off). I slowed back down to highway speeds and noticed that when the throttle was pressed, it ran much rougher than normal. Pulled over, shut it off, restarted. It cranked longer when starting, and idled quite rough. When driving at speed and letting off the throttle, I notice "pops" coming from underneath the Jeep, does not pop when throttle is pressed. Acceleration gets rougher until I feel boost kicks in, at which point everything seems to smooth out. Wide open throttle is the only thing that feels normal, but when I let off it is back to rough and popping.

Did I damage the supercharger? Is it engine internals? (I assume not since WOT feels fine). I am out of ideas.

Please help!
 
#5 ·
6lbs of boost
No error codes
No a/f gauge
36 degrees out
Exhaust sounds choppy, smells like exhaust
No fluids leaking
There is a metallic sound coming from under engine bay at idle which is also new, and also noticed that the interior lights are flickering when at idle now.
 
#12 ·
Running a supercharger on a stock engine WITHOUT an a/f guage...you asking for problems man. Even if you tuner did do a super safe tune, how would you kno your running lean if say you BAP quits or malfunctions?? you wouldnt untill you wreck something.
 
#14 ·
It's not running a BAP, I was assured by installer and magnuson that one is not necessary at 6lbs boost.

It was much warmer when tuned, this is the first winter the Maggie has seen.

Its not looking good the longer I think about the possibilities.

Check engine light came on when I was just out. I am out of town and don't have access to my trinity, so I will get the code pulled tomorrow and update the thread.

I am afraid I might need a new engine with some free flowing heads and a blower cam.... darn...

My credit card is melting at the thought of it.... already need a new tranny...
 
#18 ·
I read it. I heard it. I knew it. I had plans on doing it, have the pillar pod already, have links saved to buy an AFR gauge. I was planning on doing it the same time I was going to change the pulley to 8lbs and get it tuned again. If it made it that far, not sure the dyno session would have gone well...

Back to original question, what might have I broken? Is it safe to drive it 200 miles home? Should I have it towed?

Who has deals on long blocks right now?
 
#19 ·
You have either broken a ringland on a piston or burned a hole in a piston. My guess is you've lost a cylinder for sure. You can start by checking your plugs. I'd start with number 4 and 6 cylinders first. They like to break first for some reason. While you're checking plugs, I'd do a compression test also. Good luck man but it don't sound good.
 
#20 ·
Call Demon Performance for long block deals. As for the AFR, you said you have a Trinity, just get a LCM-1 sensor from Aeroforce and wire to a 2.5mm stereo jack then plug into the Trinity. now you are easily monitoring and logging and the most cost effective way!
 
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#22 ·
Take it real easy , AND THIS SHOULD BE ANOTHER HEADS UP FOR THOSE WITH NO AFR GAUGE .
 
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#28 · (Edited)
That is an o2 sensor code.. Probably one of the ones in the rear on either Bank 1 or 2.. Yup should be the drivers side o2 sensor right after the cats. If this is all you have that went bad then I would consider you lucky man. Don't wait any longer and get that Wideband installed...
 
#32 ·
Sounds to me like you melted a cat. It would explain everything you have described including running rough but not in WOT. If you have a big restriction on one side, your front O2 sensors could be reading very differently, this will cause crazy vibration at idle and regular driving. At WOT the PCM doesn't reference the O2 sensors so it would smooth out some.

Running up to 140 I'll bet means you were WOT for a relatively long period of time, at boost your EGTs are probably really high and burning up a cat is not at all out of the question.
 
#34 ·
Do you have motor oil all over the engine bay? if not then you didn't break a gland or burn a hole in the pistons as oil would've flown all over. especially if you have vent breather. and yes a fouled O2 sensor can cause it to idle rough & smooth out on highway. I don't know why they want to SCARE the shit out ya rightaway. :p but check the easiest things 1st for possible idle problem. pull your plugs as you may have also fouled 1 or 2. if engine doesn't sound bad - meaning marbles tumbling - then, you may be in better shape than you think. :rolleyes:
 
#37 ·
No motor oil in the engine bay, or leaking on the ground. It does sound like something tumbling around the bottom of the engine, like pieces of metal.... so while I would like to be optimistic, and think it's a cat or an O2 sensor, I don't think I'm that lucky.

We'll see what happens next week when I can get it in to be looked at.
 
#39 · (Edited)
X2 Brian is correct. I had a piston that looked like that aswell and no oil anywhere under the hood...that doesnt even make logical sense to begin with buddy:/
 
#44 ·
Well it made it the 200 miles home...

After driving it more I am not sure how it could be a piston if it still performs fine at full throttle. It doesn't make sense to me.

Should I take it to the dealer and try my luck with warranty or to my installer/tuner and say wtf?
 
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