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#1 10-17-2008 01:12:24

john
Enthusiast
Registered: 09-27-2008
Posts: 107

Re: A New Vibration Problem...

When I drive to work, I often have to go up and down steep hills. When
I go up the hill and there's added torque to my engine, I get a
vibration that I don't get if the road's flat. It feels like it's
coming from the rear of my Jeep. Does anyone know if this is something
mechanical? So far, I know my Jeep needs a new alternator and
powersteering pump in the near future, PCV valve and maybe a catalytic
converter. There's usually a strange smell inside my Jeep Cherokee
after I accelerate hard to pass someone uphill.

If it's not my cat, then could someone tell me other signs to look out
for to make sure my catalytic converter would need replacement?

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10-17-2008 01:12:24

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Re: A New Vibration Problem...

#2 10-21-2008 23:05:29

arden
Newbie
Registered: 10-05-2008
Posts: 9

Re: A New Vibration Problem...

A volt gage in the dash may not be as accurate as you would like.  Find a friend with a meter or some parts stores will check them for free for you if yo pull it and take it in.  When your using lots of juice with fans and lights, the voltage will go down.  as long as it is equal or greater than 12.5 volts, the battery will charge.

Your PCV valve is probably doing fine.  Take off the engine and shake it.  If it rattles it is fine.  I am assuming you have high miles on the engine.  When cylinders wear, the rings don't fit as tight and allow "blow by".  This is usually oily and needs to be vented so that you  don't have excessive pressures build up in the crank case.  The PCV vents this pressure to the air cleaner and so yo see oil on the air filter.  Your vibration may be from the engine, check the compression first before yo go spending money.

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#3 10-21-2008 23:08:52

john
Enthusiast
Registered: 09-27-2008
Posts: 107

Re: A New Vibration Problem...

If it is a compression problem, how easy would it be to fix? After I
get going on highway speeds..... it then becomes alot more difficult
to pass going uphill. The Cherokee I have has 180k miles.

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#4 10-21-2008 23:15:23

stellarxj
Rookie
Registered: 10-05-2008
Posts: 73

Re: A New Vibration Problem...

Compression problems are mostly fixed with a valve job.  The oil blow by can be reduced by running heavier oil and good old STP oil treatment.  I am assuming you are using oil also.  One thing that will happen is that your plugs will become fouled, which may contribute to a lack of power.  Valvoline racing oils are never on sale, but they are formulated to burn in race engines without leaving ash deposits on the plugs.  I almost always run 20W50 in my engines.  You sacrifice a little on the milage, but make it up in less engine wear.

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10-21-2008 23:15:23

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Re: A New Vibration Problem...

#5 10-22-2008 20:41:24

john
Enthusiast
Registered: 09-27-2008
Posts: 107

Re: A New Vibration Problem...

My engine does tap. However, it sounds like it goes away at around
1.5 rpm. Is it expensive to change the valves? When I did change my
plugs, they did have black tips on them. I'm running Platinum plugs
now. I didn't think I heard the tapping so much when I used 10w30
oil. I'm using 5w30 now. Wouldn't running 20w50 oil further ruin my
valves? I'll look into having the valves replaces as long as it's not
hard to do. They complain when they have to do something to any of my
vehicles at work unless it's fast and simple.

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#6 10-22-2008 22:29:26

chuck
Rookie
Registered: 10-22-2008
Posts: 66

Re: A New Vibration Problem...

Heavier oil will not affect the valves themselves.  It will however, within reason, give your bearings longer life and reduce smoking from worn rings.  Your plugs should have a light beige color.  There are two reasons to run 5W30 or 5W20.  One is very cold weather or getting good gas milage.  It is in all the new cars for the milage ratings.  You won't have any trouble with 20W50 sown to zero degrees.  That is as cold as I have had a chance to run it.  Also, it might reduce that tap you hear. 

The only reason to replace valves is if there is a hole in them or the stem is bad.  Normally they grind them and knurl the guides, and put on a new set of seals for under $200 including gaskets.  I can almost guarantee you with 180K on the motor it will run better and smoother.

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#7 10-28-2008 21:38:42

mark
Rookie
Registered: 10-05-2008
Posts: 50

Re: A New Vibration Problem...

I agree on running heavy oil in older engines. My '92 4.0
has 245K on it and I run 20W50 in the summer and 10W40 in the winter
here in suburban Philadelphia. I'd think New Hampshire winters are
even colder...

As far as oil consumption is concerned, I've been getting about a
quart every 1,200 miles. From what I've read, the Wal-Mart
store-brand filter (made by Champion Laboratories, makers of STP
filters) is far better in quality than Fram filters.

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#8 10-29-2008 13:43:29

john
Enthusiast
Registered: 09-27-2008
Posts: 107

Re: A New Vibration Problem...

I haven't used any oil in my Jeep. I keep up regular with the oil
changes and the first thing I do is check my oil level prior to
starting the oil change. I am losing alittle bit of tranny fluid
through the pan's gasket.

I didn't go to work today due-to the lack of sleep so I'm going to try
to change jobs. I have a baby on the way and the money I'm making now
is barely enough for us to get by. I have alot of baby stuff to buy
and $280/week isn't cutting it. If my hours weren't cut, I'd be making
over $400/week. That's what I was used to.

If I did do an oil change and used 20w50 oil, would I notice a
difference in how my Jeep drives?

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#9 10-30-2008 15:33:43

deerhuntxj
Helper
Registered: 10-05-2008
Posts: 30

Re: A New Vibration Problem...

No

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#10 10-30-2008 15:34:16

john
Enthusiast
Registered: 09-27-2008
Posts: 107

Re: A New Vibration Problem...

Thanks. Then I'll try the 20w50 oil the next time I get to do an oil
change at work. Should just be another 2 weeks before I do that.

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#11 10-30-2008 15:34:47

rapsen
Helper
Registered: 09-27-2008
Posts: 20

Re: A New Vibration Problem...

My most humble of opinions......

First thing you need to consider is the age of your engine. 180K is a
lot of miles on any motor and by this time it is usually best to
either rebuild the original engine or have it replaced with a rebuilt
one (long or short block). You must take stock of the internal
condition of your engine: connect a vacuum gauge to a source of
manifold vacuum and you'll see a nice display of various internal
maladies ranging from stuck or floating valves to worn rings; do a
compression check and see if there are any cylinders with very low
compression (the general rule is that the cylinder pressures
shouldn't vary by more than 25% of each other). Look these tools up
on the web and how to use/interpert them....

Doing a valve job by itself will do two things: 1)it will not prevent
your excessive blow-by condition and; 2)it will invariably increase
your blow-by because now you have a nice tight top end (cylinder
head) with a loose bottom end (your rings, pistons and cylinders are
all worn to the tune of 180K). Yes the valves will seal nice and
tight but this will simply put more stress on the mileage-weakened
bottom end...your old rings will not be able to seal against the
increased compression pressure made by your rebuilt cylinder head due
to wear. If your main and crank bearings are worn, you'll just
accelerate their wear process by rebuilding the top end.

The 4.0L, as mentioned does not have a PCV...it uses a Crank Case
Vent system (CCV). The crankcase gases are drawn out through the rear
elbow fitting while the front fitting allows filtered air into the
cranckcase. If the rear fitting/hose is plugged then blow by gases
will be entering your air-filter box. You will need to remove the
valve cover, hack out the hardened rubber grommets and clean both
elbows and air lines. The grommets can be gotten from the
stealership...not too expensively. While you're at it, the rubber
valve cover gasket should be replaced as it has probably turned to
stone and leaking out the back end. NAPA has them for about $30.

Your vibration could be worn U-joints...are they original? Could also
be a transmission problem as the lock-up portion of the torque
converter slips or comes in and out of lock up.

Have your alterantor tested. Give the beastie a good tune up...you
know wires, cap, rotor, plugs, filters etc.

Just some of my 2 cents.....

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#12 10-30-2008 22:56:16

john
Enthusiast
Registered: 09-27-2008
Posts: 107

Re: A New Vibration Problem...

Thanks for the help. I'm supposed to have a mechanic at work go
through the entire drivetrain to find the cause of the vibration. I
don't think it's my torque converter. If I'm in "drive" and let off
my brakes, the engine can pull itself at a normal speed. I'm not
completely sure if I do have the oil blow back or not because I have
good oil pressure when I'm driving and it's not losing any oil at
all. If I did an oil change today, the level would be right where it
was when I completed my last oil change. The U-Joints are more than
likey original. That could be the vibration more than likely. I'm
going to try to shake the drive shaft when I'm working today. Wish me
luck!

Even if it does have the blow back of the oil problem, that doesn't
mean the engine is close to dying, right? I've heard from many people
that the 4liter straight 6 by Chrysler is hard to kill.

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#13 11-04-2008 13:29:20

matt
Helper
Registered: 10-05-2008
Posts: 20

Re: A New Vibration Problem...

Just a thought.... what makes you think you have a "blow-by" problem?

If you are getting oil in your airbox, then you most likely have a
plugged CCV system.....you may not have a blow-by problem at all.
Cleaning the elbow fittings and hoses and replacing the valve cover
grommets and gasket should solve that problem.

The 4.0L is a very stout engine because it is designed for longevity.
It's definitely a lo-po motor...the compression ratios are low, it is
set up with a mild state of tune and as such will last a good long
time given a modicum of care.

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#14 11-04-2008 13:29:58

john
Enthusiast
Registered: 09-27-2008
Posts: 107

Re: A New Vibration Problem...

Next Friday, I'm buying the new tube piece that goes
from the air filter to the valve cover. My engine doesn't always tap.
It didn't do it at all for the past 2 days and I believe my valves
are actually fine. I'm also going to have them at work finish my tune
up by installing a high voltage coil, checking the timing on my
engine, fuel filter and whatever else may be the problem.

About the vibration, I'm buying new tires at work for now until I
lift my Jeep. I'm buying 225-75R15 Kelly Safari Trex. They're
excellent against hydroplaning and another guy I work with has them
on his S-10 truck and loves them. Perhaps my vibration is just in my
tires, but they are still going to go over my drive train for me when
they get time at work. Thanks for all the advice.

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