Novak Conversions Jeep Wrangler TJ engine mounts

Sudden loss in power

IronCity

IronCity

TJ Enthusiast
Original poster
Joined
Dec 8, 2016
Messages
438
Location
NJ Toms River, NJ, United States
I'm experiencing a loss in power while driving on the highway in 5th gear. This is a new problem so its not the tire size or gears. I'm running a 4.0 manual trans with 31x10.5 15"s and stock gears. I was on my way to work this morning hit 65 in 4th gear, shifted to 5th and I started to lose speed. I floored it and still dropped speed. I've never had a problem maintaining a speed of 70+ in 5th gear. I drive the parkway on the regular. I've recently changed the oil, front and rear pinioned seals. No leaks great oil pressure. Air filter seems ok also.


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IronCity said:
I'm experiencing a loss in power while driving on the highway in 5th gear. This is a new problem so its not the tire size or gears. I'm running a 4.0 manual trans with 31x10.5 15"s and stock gears. I was on my way to work this morning hit 65 in 4th gear, shifted to 5th and I started to lose speed. I floored it and still dropped speed. I've never had a problem maintaining a speed of 70+ in 5th gear. I drive the parkway on the regular. I've recently changed the oil, front and rear pinioned seals. No leaks great oil pressure. Air filter seems ok also.


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This makes me think possibly a cracked exhaust manifold. Outside of that, you should probably start with a compression test.

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I had a clogged cat on a mustang years ago and after "driving" around the cat would be glowing cherry red. I would have serious power loss, got so bad the car would have a hard time turning on.
 
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Okay guys, I'm revising this thread. While driving in to work this morning on the parkway my loss of power issues reared its ugly head again, this time worse. I could not maintain speeds in 5th so I drove in 4th. Now I'm losing power in fourth, how much is a compression test and could it be an O2 sensor? No lights on dash or codes.
 
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IronCity said:
Okay guys, I'm revising this thread. While driving in to work this morning on the parkway my loss of power issues reared its ugly head again, this time worse. I could not maintain speeds in 5th so I drove in 4th. Now I'm losing power in fourth, how much is a compression test and could it be an O2 sensor? No lights on dash or codes.
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If a Cat is clogged, you will see a decrease in engine vacuum as rpm increases due to back-pressure building up.
With a severely plugged Cat, and vehicle parked, vacuum can be observed to go away as soon as throttle is advanced off-idle.
If you have a Vacuum Gage or Scan Tool you can see it easily.
 
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So, I bought my LJ back in Jan this year... it was running great and was getting about 190-200 miles to the tank (~12 mpg)... two weeks ago I got a P code to replace my B1S1 O2 sensor... since this jeep has 118k miles on it I thought to replace all O2 sensors while I am it since I dont know the last time the previous owner replaced them. I followed the other forum about replacing the Bosch sensors with NTK... Now, I'm getting at best about 150-160 Miles to the tank (~9 mpg). Nothing else changed, I'm not getting any engine light... but one thing I did notice is the response to acceleration is sluggish...

I dont know what to do or check.. please help.
 
Novak Conversions Jeep Wrangler TJ engine mounts
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