Pirate 4x4 banner

1 - 7 of 7 Posts

·
Registered
Joined
·
1,086 Posts
Discussion Starter #1
I'm a Yota guy, but my buddy just bought an '81 Cherokee with a 4.2, TF727, NP208. Well, the engine seems to run good when not driving, but as soon as it's under load, it's got no power. Truck won't get over 40mph, and has no balls. I sure the 4.2 in a fullsize cheroke isn't going to be a rocket, but this thing is a serious dog. Any ides as to what the problem might be. Feel free to flame my stupid question without enough details, but It's all I got right now:D

Thanks, Jesse
 

·
Registered
Joined
·
1,981 Posts
1) it's an inline six, they aren't spectacular to start with. Not bad, but not spectacular (especially by the V8's that the standard around this BB).

2) I would check timing first off. I believe spec on most of them is 9*BTDC.

3) If timing seems to be OK, next I would do is check for slop on the timing chain. If it's OEM, the sprockets were PLASTIC (I shit you not), and they wear quickly. You can get an idea of this by looking at the advance characteristics under a strobe.

4) Would start looking at ignition second. Plugs, wires, ignition box. CJ's have notoriously bad ignitions. Do a search on TFI Upgrade, do that and slap a tune-up and MSD ignition box on it.

5) start looking at drivetrain next, but I know zip about slush-boxes.
 

·
Premium Member
Joined
·
1,302 Posts
Also, if you can't get the rpm's up under load then the cat might be clogged. You can try to pull the O2 sensor and drive it. This will release the back pressure if ther is any. Don't worry about running without the O2 it won't hurt anything.
 

·
Registered
Joined
·
589 Posts
I might be wrong about this but didn't they start with the O2 sensors in 1983? If you have a cat, I'd put my money on that as your problem. Also, check your entire exhaust system for obstructions.
 

·
Registered
Joined
·
1,759 Posts
my guesses:

1) timing problem. advance the timing until it spark-knocks under load and then back it off some. check and see how much slop is in the timing chain by doing this:...now i can't find it. you pull the cap, roll the engine over by hand until the timing mark on the damper is at 0ºbtdc and then roll it backwards until the rotor starts moving again, then look at the mark in ref. to the timing marks. this will tell you how many degrees of slop there is. i don't remember how many deg. is bad...maybe someone else does.

2) check the cat.

3) make sure the vac. advance is working and there are no big vacuum leaks.

4) check the carb and maybe hose it down with carb-choke cleaner.

matt
 
1 - 7 of 7 Posts
Top