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Weak @3000 RPM/No power

908 views 7 replies 5 participants last post by  unhumen 
G
#1 ·
Where should I start? She runs great until reach in any gear 3k rpm. Is it the carb, the fuel pump, the filter, vacuum advance, the timing? I usually notice this on acceleration through the gears. CJ7,5speed, straight six 258.Any help?

 
#2 ·
My first step in solving that problem was to purchase a K&N air filter. I still lose a little bit of power at 3000 but not as much as before. Mine will now run up to about 3600 rpms with out bogging down too much, before it only went to about 2900. Also try one of the ignition upgrades mentioned on this bbs. That is my next step.
B
88 YJ, 258 sick cylinder, crapper bbd

 
#3 ·
I would start by having a long look at the ignition module and coil....
If it was a fuel problem, it would happen sooner under 3,000 rpm under heaver loads, and later under lighter loads. If it were a weak fuel pump, the heavy loading would use more fuel faster lite load at a higher rpm.


If it does it at almost the same rpm every time, regardless of load, it almost has to be ignition module or coil break down... maybe even a bad pickup coil in the distributor.

I've noticed more and more DuraSpark modules going south by just not letting the engine rev up. (They used to just quit, and that was that!)
I have two on the bench right now that start to fail at 2,000 and quit completely by 3,200 rpm.
They start getting spotty and randomly misfire around 2,000 to 2,500, so it looks all for the world like the engine just doesn't have any power.


Just some suggestions, Aaron.

If Chris Columbus "Discovered" America (with 25 million already here), Can I Go "Discover" Florida?
 
#5 ·
I recently had something similar. I thought it may be related to timing, but that normally would be low rpm under load (or acceleration). Lucky for me I had been hearing the catalytic converter rattling a little. I was on the freeway and only had power in the lower rpms. Since it had been raining I check all the wires....dryer than a bone. The cat was clogged with a piece of metal that had rattled off. It idled great. Clean untill about 2,500 rpms, and then nothing. I was surprised that the exhaust could 'shut it down'.

For what it is worth.

-raymo

 
#8 ·
If it just started and nothing else was changed and you do have a cat. check that first sometimes you will hear it pinging or ratteling.the junk inside breaks down and clogs the exhaust .It will sometimes get RED HOT if blocked enough.
good luck.

Learn to let go of what does not serve you ,but forces you to serve it
 
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