• Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Not running right

9

92jeepxjOR

NAXJA Forum User
Location
Salem Or
Ok, ive been dealing with this for a month or so.My jeeps just not running right.when its at an idle it has a miss to it,it gets better as the rpm's get higher but it still fells like its lacking power.ive done all the basic tune up stuff and it didn't help.I'm just wondering if anybody might have any ideas???
 
a miss and lacking power are 2 different issues.

a miss is usually a loss of fuel or spark.

when you did the tune up, what color were the plugs? was the condition/color of the plugs different then the others?

how old is the cat convertor.

have you cleaned the throttle body and IAC.

how about a topend/combustion chamber cleaning, ie seafoam treatment.

have you tested any of the sensors? any stored codes or CEL
 
3 of the plugs get oil deposits on them after a month or so,the cat is most likely the stock one. It doesn't throw any codes. TB is clean,I haven't checked any sensors,I'm not sure how to do that
 
does the engine have blow by?

was there oil on the air filter?

oil could be coming from the intake(blow by), worn valve guides, or worn rings which can result in compression issues.

does the engine blow smoke out the exhaust at start up?

oil deposits or carbon build up on the plugs?
 
No smoke on start up,very little blow by,I'm pretty sure the valve guides aren't in the best shape.will the valve guides being bad cause it to not run right?
 
92jeepxjOR said:
No smoke on start up,very little blow by,I'm pretty sure the valve guides aren't in the best shape.will the valve guides being bad cause it to not run right?
Click to expand...

smoke out the exhaust on a cold start up is an indication of worn guides/seals as the oil will leak from the head into the combustion chamber.

once the engine is warmed up, any oil that gets past the guides/seals will show up as smoke out the exhaust. if you can see the smoke then they are really worn and could cause problems.

if your engine doesnt puff at cold startup, i doubt yours are worn.

what did your basic tune-up consist of?

is there oil in the intake or in the throttle body if you look past the throttle plate?

how old is the o2 sensor?

how many miles on the engine?
 
Tune up was plugs,wires,cap,rotor,and fuel filter.the o2 is less than a year old. There was a little oil in the intake last time I had it off.the motor has just under 160,000 on it
 
if your not gettting any codes and the sensors spec out out, i would check the ground from the battery to the block and renew the ground strap from the head to the firewall.

also clean the IAC, it could be getting hung up causing some idle issues.

make sure the cat convertor is ok, but if its the original 18 year old one, i would look into replacing it.

if this doesnt clear things up, i would do a top end treatment(seafoam or gm/mopar top end cleaner) through the brake booster vacumn line.
 
A compression test on all cylinders is never a bad idea and in about an hour, you'll have a good snapshot of the internal condition of the engine.

Get a good quality compression tester (they can be rented from parts stores if you don't have one) and get r done. The compression specs for the 4.0 are 120-150 psi, with no more than a 30 psi variation between cylinders.
 
You must log in or register to reply here.

Similar threads

R
93 manual xj intermittently not going into gear
Replies
4
Views
2K
cruiser54
C
J
Running just fine then dies at idle on street
Replies
4
Views
2K
90xj06
9
P
2K IDLE - Odd Shifting - TPS? (I know.. I know)
Replies
3
Views
2K
Unclewolverine
U
J
01 XJ Not Reaching Operating Temp
Replies
18
Views
2K
JMA_2001XJ
J
M
Oil pressure question
2
Replies
26
Views
3K
Money_Pit_Incoming
M
Back
Top