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Unread 10-30-2009, 07:02 AM   #1
atomicflatulenc
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1985 CJ7 
 
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Strange loss of Power...need help diagnosing

I've been having an issue lately with my 96 4.0L ZJ.

When I go over small bumps in the road, I sometimes lose engine power.

I need to find a direction to start from. Sensors maybe?

The only other time it will do the wierd thing is after I drive the 30 minutes at about 45...park and pick up my son...when I first accelerate it starts to go for a second and then nothing...I have to let up on the gas and then push the peddle back down to start accelerating again.

I've tried just keeping the peddle pressed and the ZJ just hesitates and won't go until I let up on the gas and try agian.

Weird...

Tell me someone has had this issue! Help!

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'85 CJ7, 258 4.2 Howell TBI, NP435, twin sticked Dana300, 4.56 Yukon chromoly: Rear20-extra thick tubes, shaved,trussed,discbrakes,ARB: Front30- flipped tierod,Detroit EZ locker, warn hubs: 3.5" BDS YJ springs and booster, 35" Trxus M/T's, rhino'd, full roll cage, borgenson steering shaft, big daddy steering box bracket...Unknown OIL Leak(working on it...)
FOR SALE $6000
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Unread 10-30-2009, 07:20 AM   #2
4Slow9erHybrid
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Quote:
Originally Posted by atomicflatulenc View Post
I've been having an issue lately with my 96 4.0L ZJ.

When I go over small bumps in the road, I sometimes lose engine power.

I need to find a direction to start from. Sensors maybe?

The only other time it will do the wierd thing is after I drive the 30 minutes at about 45...park and pick up my son...when I first accelerate it starts to go for a second and then nothing...I have to let up on the gas and then push the peddle back down to start accelerating again.

I've tried just keeping the peddle pressed and the ZJ just hesitates and won't go until I let up on the gas and try agian.

Weird...

Tell me someone has had this issue! Help!
Try disconnecting the upstream O2 sensor (the one before the catalytic converter). Drive around for a few days and see if these symptoms disappear. If they do, you need a new GENUINE MOPAR sensor!!! Don't experiment with Bosch and other brands. The 4.0 is very picky about the O2 sensor. Remember, disconnecting the sensor is a test, not a cure! Don't plan on any 1000mi road trips with disconnected sensor.
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Unread 10-30-2009, 07:34 AM   #3
atomicflatulenc
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Do I need to get the MOPAR sensor from a dealer?

I did change the sensor back in june with a NAPA O2 sensor.
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'85 CJ7, 258 4.2 Howell TBI, NP435, twin sticked Dana300, 4.56 Yukon chromoly: Rear20-extra thick tubes, shaved,trussed,discbrakes,ARB: Front30- flipped tierod,Detroit EZ locker, warn hubs: 3.5" BDS YJ springs and booster, 35" Trxus M/T's, rhino'd, full roll cage, borgenson steering shaft, big daddy steering box bracket...Unknown OIL Leak(working on it...)
FOR SALE $6000
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Unread 10-30-2009, 07:32 PM   #4
Jeep2k55
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I have noticed that if you have a leak in your transfer case and you lose fluid, you will also lose alot of power. Happened to me. Found out by accident. Had major power loss...felt gutless. And was doing random maintenance on it and decided to service the TC. Realized it was extremely low on fluid. Filled her back up and took her for a drive and the power was back. Maybe it was unrelated? I don't know for sure but that's my expirience
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Unread 10-30-2009, 08:03 PM   #5
JesseOR
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Reading the title, I would say Cat, but the symptoms you described, almost rule it out....
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Unread 10-31-2009, 09:13 AM   #6
atomicflatulenc
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What cat... The only cat might be dead under the hood.
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'85 CJ7, 258 4.2 Howell TBI, NP435, twin sticked Dana300, 4.56 Yukon chromoly: Rear20-extra thick tubes, shaved,trussed,discbrakes,ARB: Front30- flipped tierod,Detroit EZ locker, warn hubs: 3.5" BDS YJ springs and booster, 35" Trxus M/T's, rhino'd, full roll cage, borgenson steering shaft, big daddy steering box bracket...Unknown OIL Leak(working on it...)
FOR SALE $6000
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Unread 10-31-2009, 09:27 AM   #7
JesseOR
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Quote:
Originally Posted by atomicflatulenc View Post
What cat... The only cat might be dead under the hood.
Sooo, am I to gather from this that you cut out the CATYLITIC converter?

Because a clogged CAT will result in massive power loss.
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Unread 10-31-2009, 09:44 AM   #8
ZeeJay1997
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Quote:
Originally Posted by atomicflatulenc View Post
When I go over small bumps in the road, I sometimes lose engine power.
Try gently wiggling PCM connectors while engine running cold and see if you get hestitation.

Also try gently tapping the fuel pump, ASD, and tranny relays in the fuse box under the hood.
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Unread 10-31-2009, 09:59 AM   #9
atomicflatulenc
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Cat was all broken up inside and clogged. Its not anymore...

I need a babysitter, or I'll never get this solved!
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'85 CJ7, 258 4.2 Howell TBI, NP435, twin sticked Dana300, 4.56 Yukon chromoly: Rear20-extra thick tubes, shaved,trussed,discbrakes,ARB: Front30- flipped tierod,Detroit EZ locker, warn hubs: 3.5" BDS YJ springs and booster, 35" Trxus M/T's, rhino'd, full roll cage, borgenson steering shaft, big daddy steering box bracket...Unknown OIL Leak(working on it...)
FOR SALE $6000
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Unread 05-18-2010, 08:38 AM   #10
atomicflatulenc
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still having trouble with this and its getting worse...
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'85 CJ7, 258 4.2 Howell TBI, NP435, twin sticked Dana300, 4.56 Yukon chromoly: Rear20-extra thick tubes, shaved,trussed,discbrakes,ARB: Front30- flipped tierod,Detroit EZ locker, warn hubs: 3.5" BDS YJ springs and booster, 35" Trxus M/T's, rhino'd, full roll cage, borgenson steering shaft, big daddy steering box bracket...Unknown OIL Leak(working on it...)
FOR SALE $6000
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Unread 05-18-2010, 12:16 PM   #11
murphydajeep
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Quote:
Originally Posted by ZeeJay1997 View Post
Try gently wiggling PCM connectors while engine running cold and see if you get hestitation.

Also try gently tapping the fuel pump, ASD, and tranny relays in the fuse box under the hood.
I would think loose connection too, if it happens when your hittin a bump it could be jostling your connector around just enough to mess it up for a second. If it was a clogged cat wouldnt it be a consistent loss of power, almost sounds like your having a fuel delivery issue....bad map sensor, dirty intake?

When all else fails bust out the hammer and start hitting things that look like they are givin you the eye, swearing helps too, Percussive maintenance ftw.
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Unread 05-18-2010, 07:19 PM   #12
classicmetalman
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Quote:
Originally Posted by murphydajeep View Post

When all else fails bust out the hammer and start hitting things that look like they are givin you the eye, swearing helps too, Percussive maintenance ftw.
Too funny I'd lean towards a loose connector somewhere
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Quote:
Originally Posted by murphydajeep View Post
I say you should still hit something just to let it know you mean business, or shake a hammer at it in a menacing fashion
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Unread 05-18-2010, 08:27 PM   #13
rooster51
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Im thinking, in no specific order, PCM or coil or CPS or any combination of the 3.
Happy hunting!
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Unread 05-19-2010, 07:12 AM   #14
atomicflatulenc
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Replaced the cap, rotor, plugs and wires last night. No issues on the test drive, and no issues for the 40 minute round trip to the babysitter's.

Not gonna say its fixed yet. Maybe if I go a week without a powerloss I'll say its fixed.
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'85 CJ7, 258 4.2 Howell TBI, NP435, twin sticked Dana300, 4.56 Yukon chromoly: Rear20-extra thick tubes, shaved,trussed,discbrakes,ARB: Front30- flipped tierod,Detroit EZ locker, warn hubs: 3.5" BDS YJ springs and booster, 35" Trxus M/T's, rhino'd, full roll cage, borgenson steering shaft, big daddy steering box bracket...Unknown OIL Leak(working on it...)
FOR SALE $6000
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Unread 05-19-2010, 09:23 AM   #15
murphydajeep
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Quote:
Originally Posted by atomicflatulenc View Post
Replaced the cap, rotor, plugs and wires last night. No issues on the test drive, and no issues for the 40 minute round trip to the babysitter's.

Not gonna say its fixed yet. Maybe if I go a week without a powerloss I'll say its fixed.
I say you should still hit something just to let it know you mean business, or shake a hammer at it in a menacing fashion
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