Low power 99 Wrangler 4.0, compression? - JeepForum.com
 
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post #1 of 10 Old 07-29-2010, 10:00 PM Thread Starter
TJMistress
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Low power 99 Wrangler 4.0, compression?

Runs smooth as silk at idle, just no power over 2000 rpm. It acts like the timing is off but I checked to make sure the timing chain didn't skip a tooth, its fine. After rechecking my compression with the proper extension for my gauge the compression reads 118-125. Is this too low? Fuel pressure at the rail is good. It has new plugs, wires, cap and rotor.

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post #2 of 10 Old 07-29-2010, 10:12 PM
wushaw
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Check your cat, it could be clogged. Your compression is fine.
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post #3 of 10 Old 07-29-2010, 11:42 PM
ElementX
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2x on clogged cat

'98 TJ Sport
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post #4 of 10 Old 07-30-2010, 08:56 AM Thread Starter
TJMistress
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I'll check the cat soon. Does anyone know what an acceptable compression building rate is? All six cylinders followed this basic pattern.
Stroke 1: 60psi
Stroke 2: 90psi
Stroke 3: 110-115 psi
Strokes 4-6: 115-125 psi
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post #5 of 10 Old 07-30-2010, 12:14 PM
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Compression spefications per Mitchell is 120-150. And your checking it fine. Check the cat now.
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post #6 of 10 Old 07-30-2010, 06:09 PM Thread Starter
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Exhaust is flowing fine. Here are the next three things that in my mind should be checked. Injectors, coil, and or 02 sensors.
Any comments?

Last edited by TJMistress; 07-30-2010 at 06:32 PM.
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post #7 of 10 Old 07-30-2010, 06:58 PM
wushaw
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Did you remove the cat and see if the power comes back above 2k? Or did ya just see if it was flowing?
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post #8 of 10 Old 07-30-2010, 08:42 PM Thread Starter
TJMistress
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I took the cat and muffler out to make sure nothing was floating around and loose inside. I put it on the shop vac to see if it was flowing (it was) and then reinstalled it and put a pressure gauge in the upside O2 sensor. It stayed at zero at idle and around 1/2 pound at 3-4000 rpm. It instantaneously spikes with quick acceleration at 4 psi but is right back under 1 psi.
I guess I coulda taken it out for a spin but didn't really feel like putting the skid plate and trans mount back on, not to mention letting my redneck show through suburbia as I made my way to the freeway for a test. Since there was no back pressure in front of the cat I assumed it was fine. If there is a reason for a road test its still not back together as I have broken studs and stripped bolts from one end to the other on this thing.
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post #9 of 10 Old 07-30-2010, 09:40 PM
wushaw
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It is off and it can't hurt, it will also rule the cat out for sure.
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post #10 of 10 Old 09-28-2010, 11:23 PM
spooled
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What was your outcome on this? I am having similar issues.
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catalytic converter , loss of power , low power

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