Loss of power - JeepForum.com
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post #1 of 22 Old 02-14-2020, 06:54 PM Thread Starter
zeebart
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Loss of power

I had a shop work on my '81 CJ7 over last summer to help me get through emissions testing (I kept failing and got turned backwards with the carb adjustments). They adjusted the timing, the carb, and added a fuel regulator. They said that everything else looked really good and were impressed with the Jeep. It still has the original 4 cylinder "Iron Duke" engine. Rebuild tranny and carb. Passed eventually.

Since then it've slowly lost power. When I accelerate or attempt to climb a steep hill the power that I once had (albeit not that much, it's the 4 cylinder Duke) is not there. I hit the gas and the engine does rev, but the tranny doesn't catch up for a little while. There's a sweet spot if I don't push too much on the accelerator it will put out the torque, but it performs like my old '72 VW bus climbing the coast range.

Before I dive into possible solutions, anyone have any ideas? Timing? Carb? Loosing compression in one or more cylinders?

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post #2 of 22 Old 02-14-2020, 07:51 PM
Fourtrail
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Too much undercoating weighing you down....




Sorry, with your usename, I couldn't pass it up. You mention the motor revs then the tranny catches up so automatic? Basics, pull the plugs and post some pictures so we can see if it is running rich or lean. Also doing a compression test won't hurt.

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post #3 of 22 Old 02-14-2020, 09:21 PM
jibib
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What carb are you running on it? I had same experience on my 86 4 cyl when I put the Carter carb on it to pass smog.
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post #4 of 22 Old 02-14-2020, 10:47 PM
restorationride
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Quote:
Originally Posted by zeebart View Post
I had a shop work on my '81 CJ7 over last summer to help me get through emissions testing (I kept failing and got turned backwards with the carb adjustments). They adjusted the timing, the carb, and added a fuel regulator. They said that everything else looked really good and were impressed with the Jeep. It still has the original 4 cylinder "Iron Duke" engine. Rebuild tranny and carb. Passed eventually.



Since then it've slowly lost power. When I accelerate or attempt to climb a steep hill the power that I once had (albeit not that much, it's the 4 cylinder Duke) is not there. I hit the gas and the engine does rev, but the tranny doesn't catch up for a little while. There's a sweet spot if I don't push too much on the accelerator it will put out the torque, but it performs like my old '72 VW bus climbing the coast range.



Before I dive into possible solutions, anyone have any ideas? Timing? Carb? Loosing compression in one or more cylinders?
Simply put, it sounds like a transmission problem.

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post #5 of 22 Old 02-14-2020, 10:50 PM
RedNeckCorvette
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Nothing in your profile about you or your jeep.
Not enough information posted to help. Automatic or manual transmission?
Filling out your profile helps.
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post #6 of 22 Old 02-14-2020, 11:07 PM
restorationride
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Originally Posted by RedNeckCorvette View Post
Nothing in your profile about you or your jeep.

Not enough information posted to help. Automatic or manual transmission?

Filling out your profile helps.
I thought it was filled out. Anyway, automatic or manual transmission doesn't really make a difference. Sounds like a transmission problem either way...

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post #7 of 22 Old 02-25-2020, 03:28 PM Thread Starter
zeebart
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Manual transmission. 151 4-cylinder '81 CJ7. Trying to send a pic see if it works...
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post #8 of 22 Old 02-25-2020, 03:29 PM Thread Starter
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And here's a couple of the plugs...
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post #9 of 22 Old 02-25-2020, 03:32 PM Thread Starter
zeebart
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Trying again with the pix
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post #10 of 22 Old 02-25-2020, 03:46 PM
Fourtrail
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Plugs look ok, but i would swap them to a normal set of plugs from autolite/champion/delco, I have never been a fan of the v-power plugs, they would wear off the outer edges of the 'V' and then your gap would grow and not want to fire correctly. Like already stated though, if your motor revs up and the Jeep doesn't speed up, then you are more looking at a transmission issue. The color/smell does the ATF have when you pull the dipstick?
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post #11 of 22 Old 02-25-2020, 05:09 PM
uptillnow
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From your description of how it acts, it sounds like the transmission to me as well. "I hit the gas and the engine does rev, but the tranny doesn't catch up for a little while."

Although you have a Weber carburetor and they take some specific adjustments. This may also be a problem. "(I kept failing and got turned backwards with the carb adjustments). They adjusted the timing, the carb, and added a fuel regulator."

The plugs look reasonably good, so your carburetor, and timing, can't be that far off???

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post #12 of 22 Old 02-26-2020, 09:14 PM
BagusJeep
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clutch slip?
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post #13 of 22 Old 02-27-2020, 12:39 AM
80cj
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clutch slip?
That's what it has to be. Otherwise how can a manual trans have to "catch up"?
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post #14 of 22 Old 02-27-2020, 09:16 AM
John Strenk
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Most likely the clutch but I had the same symptoms when my rear hub started to wear on my rear axle.

But that had a grinding noise going along with it.

It would slip and catch, slip and catch and then, at the right speed, it would grab and seem fine until I made a turn again. That probably had something to do with the LSD in the rear axle.


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post #15 of 22 Old 02-27-2020, 09:22 AM
Hurricane4
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zeebart - Your Jeep has a manual transmission. You stated in your original post the transmission was rebuilt. Was a new clutch, pressure plate and throw out bearing installed at the time of the rebuild? Does your Jeep have a slave cylinder for the clutch or linkage?

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