tune up

I'm a new member here and I have a question for you guys. I'm giving my XJ a tune up this weekend. Its a 95 4.0L with 80K miles on it. I just got it a few months ago. It runs pretty well, but it has a bit of a rough idle and i think the gas milage could be a little better. I'm planning on replacing the fuel filter, spark plugs, spark plug wires (they look original), distributor cap, and rotor. Is there anything else i should check, look for, etc. I'm not sure if the O2 sensor has been replaced or not so I might go ahead and change that too. Is there a certain brand of wires, plugs, etc that i should buy? Oh yeah, I'm going to take a look at the throttle body and see if it needs cleaning. Thanks in advance.

Your list is a good one. I personally would leave the plug wires and check them to make sure the resistance across each is fine. If not then replace. I like regular champion plugs in mine, nothing fancy and definetly no platinum. I would clean the throttle body and I would also change the air filter and oil, gear oil, and trans filer and fluid (assuming you have no record of when any of it was done).

If you still have a rough idle then search the boards for sensor issues like TPS, MAP, etc. they should give you a good idea of where to start if the tune up does not resolve it.

Michael

Why not platinum plugs? (Besides the cost.) Just curious.

I Like Autolite Plugs Myself. As For The Rough Idle You Might Try Some Injector Cleaner. And Check All The Sensors You Can. I just Took out my injectors to install some Ford Mustang 4.7 Liter Injectors. Well Needless to say My Jeep Runs better now then when i bought it. LOL I had just relaced my injectors about 2 years ago, so I didn't expect any big change in my motor except for some horsepower and mileage. But It Idles Like Its Brand new.

Mostly my XJ´s seem pretty easy on plugs. I change them periodically (unecessarily). Just bought a used XJ with Bosch plugs in there, serious ignition issues, the stock Champions worked a whole lot better.
Stock Jeep wires, are pretty good stuff, I´ve changed a few sets, that I´ve dug out of the junk boy and used again, after the replacement wires wore out.
Distributor cap corrosion, seems to be a major cause, of rough idle, among some other things (sticky injectors).
I downloaded the maintenace schedule for my XJ, and am slowly but surely, doing the whole list, just to know where I´m at.
I periodically check all the vacume lines, top and bottom, with a flashlight. Have often found chaffed or worn spots.

xj88 what year mustang fit.

Thanks for all the input guys, I'm planning on doing it this weekend. I'm currently running a bottle of techron fuel system cleaner through it. I don't know if it will be enough, but it can't hurt.

Careful when cleaning the throttle body

The sensors in it are plastic. Two ways to do this, one is to use a spray cleaner and with the engine running and your thumb on the throttle, spray the cleaner in keeping it away from the sensors. Second method and the better one is to remove the throttle body and remove the sensors from it, clean it on a work bench with plenty of cleaner then reinstall.
As for the injectors I noticed the other nite that the local National Auto parts store had one of the 3m injector cleaning kits in for $77 and $22 for a refil kit that consisted of a can of fuel/cleaner for the kit and two other cleaners, one a gas tank pour in and the other a top engine cleaner.
As for the plugs, stay with the stock champion from the dealer, I noticed some differences between the dealer supplied champions and the ones from an auto parts store, same part number but different looking plugs with thinner ceramics and electrode.
I also use dealer supplied cap, rotor and wires however mopar does have a high performance wire for the 4.0 that are a few bucks cheaper than the stock wires.
Might want to consider a full weekend program, drain and flush the cooling system with a 7 hour flush, replace the thermostat, pressure cap, hoses [all of them] and then refill. New serpentine belt too if the existing one is of unknown age.
Grease it and don't miss the zerk in the middle of the front driveshaft, it has one
Also if the original owner replaced the universals you might have zerks on them also, need to look.
Check tire pressure, low pressure on the hiway will hurt milage quite a bit.
I just did my 'winterize routine' last weekend and am now all set for winter , still need to stick the winter wipers on though and I will probably pick up a red top this weekd if autozone still has them for $99.

First off you did not say how long you have owned the XJ, is it new to you or have you owned it since day one?

One of the best sources of what to do is the owner's manual in the glove box, you know the book most people never read. Look it over and catch up on any maintenance you are behind on. If in doubt then do all the things so you "know" what has been done.

Like others have said the wire from the dealer are resonable and very good quality. I have a dealer cap, rotor and wires on my XJ. When I tune it up at 150,000 I'll install new plugs. This time I picked up some Champion Copper plus plugs at the dealer. There have been discussions on here about how it may be a RC9YC plug but Chrysler requires stuff that the parts store plug does not have. I think I paid less than $15 for six new plugs at the dealer. The cap and rotor are also resonably priced at the dealer. You can pay more for less quality at the big box parts stores.

Guys have posted they have had poor results with the exotic metal plugs. I had my Dad and mechanics tell me to put in the engine the brand of plugs it came with from the factory. The XJ was designed for those champions so run with them.

In the days of my 69 Camero a tune up was cap, rotor, wires, plugs, fuel filter, air filter, PCV filter, cleaning the carb, transmission oil change, differential oil change, and other things that escapes my mind. Also the owner's manual said to change the shocks every 25,000 miles.

Things that are not in the manual is cleaning the throttle body, flushing injectors, and changing fuel filter. You can try driving it clean with a $10 bottle of Techron. Also you may want to change the fan belt if you are unsure of the mileage or age.

Also I have gone to 2 year oil coolant changes and I change the radiator hoses every 4 years regardless how good they look.

I have only had it a few months. I think its been pretty well taken care of but I bought it from a dealer and have no service records. To answer previous posts, I have new shocks on order and I also recently flushed the cooling system and installed a new thermostat and rad cap. I live in Atlanta and deal with a lot of traffic and she runs a little warm after idling a lot so I am have a 3 core radiator on order too. It still runs pretty well, I just think its time for a tune up. I also have a new air filter, but plan on replacing it with a K&N drop in. Whats the deal with that seven hour radiator flush? Do you drive it around until you have seven hours of drive time in it? I'm confused on that, I've seen it at the parts store before. Thanks a lot for all the responses, I really appreciate it. Oh yeah, the serpentine belt looks pretty new.

Basically there are two ways to clean out an engine, both coolant and oil passages, one method is what I call the 'shock treatment' with 15 min flush for the cooling system and motor flush, kerosene, atf for the engine. I don't like doing it that way. The 15 min coolant flush can leave 'big chunks' the same with the engine flush and those big chunks can block stuff like radiator passages and oil pickups.
The second method is a more gradual method, the 7 hour flush is one where you drain the system, refill with water and put the flush in then drive it for a total period of 7 hours. Does not have to be continous, can be 3 hours one day and 4 hours another but this method breaks the build up down in kind of the reverse order it formed in.
The first time I used it was on an 82 S-10 with a 2.6L v6. It had a side tank type radiator so I could see down one entire side. Did the drain and refill, drove from where I live in the poconos to a service call in syracuse ny, ~4 hours away. Got there and did the service call then headed back home. Took a quick look see before I headed back home and was very happy with the amount of stuff that was gone and the coolant looked almost muddy, but no chunks . Stopped about halfway home and had dinner, checked it again and I could see shiny solder, got a bit nervous the last hour or so was afraid the stuff was removing it.
At any rate got home, drained and back flushed with one of those prestone back flush kits, changed the tstat, cap and cleaned out the overflow bottle then refilled with 50/50 mix of coolant and distilled water.
One interesting note, a bad grounding system can speed up electrolysis in an automotive radiator which means that the rad and cooling system will plug up that much faster.
In the past every time I used those 15 min miracle flushes I ALWAYS ended up replacing a water pump within a couple of months. The only thing I can attribute that to is the fast flushes break so much crud loose that it acts like an abrasive water blaster and damages that packing.
As far as the engine flushes I feel the same way, those build ups did not form overnite, for long term cleaning I would use either a full synthetic oil like mobil-1 or Castrol or a 50/50 mix, the high detergent properties of the syns will gradually remove the sludge and not do it all at once. All at once could block your oil pickup and for sure will clog that oil filter faster and cause the bypass to kick in which will allow unfiltered oil to circulate. When you do run synthetic oil on a high milage engine you really need to check the dipstick more often, if you cannot read the hash marks on it it is time to change the filter.
JMO

Basically there are two ways to clean out an engine, both coolant and oil passages, one method is what I call the 'shock treatment' with 15 min flush for the cooling system and motor flush, kerosene, atf for the engine. I don't like doing it that way. The 15 min coolant flush can leave 'big chunks' the same with the engine flush and those big chunks can block stuff like radiator passages and oil pickups.
The second method is a more gradual method, the 7 hour flush is one where you drain the system, refill with water and put the flush in then drive it for a total period of 7 hours. Does not have to be continous, can be 3 hours one day and 4 hours another but this method breaks the build up down in kind of the reverse order it formed in.
The first time I used it was on an 82 S-10 with a 2.6L v6. It had a side tank type radiator so I could see down one entire side. Did the drain and refill, drove from where I live in the poconos to a service call in syracuse ny, ~4 hours away. Got there and did the service call then headed back home. Took a quick look see before I headed back home and was very happy with the amount of stuff that was gone and the coolant looked almost muddy, but no chunks . Stopped about halfway home and had dinner, checked it again and I could see shiny solder, got a bit nervous the last hour or so was afraid the stuff was removing it.
At any rate got home, drained and back flushed with one of those prestone back flush kits, changed the tstat, cap and cleaned out the overflow bottle then refilled with 50/50 mix of coolant and distilled water.
One interesting note, a bad grounding system can speed up electrolysis in an automotive radiator which means that the rad and cooling system will plug up that much faster.
In the past every time I used those 15 min miracle flushes I ALWAYS ended up replacing a water pump within a couple of months. The only thing I can attribute that to is the fast flushes break so much crud loose that it acts like an abrasive water blaster and damages that packing.
As far as the engine flushes I feel the same way, those build ups did not form overnite, for long term cleaning I would use either a full synthetic oil like mobil-1 or Castrol or a 50/50 mix, the high detergent properties of the syns will gradually remove the sludge and not do it all at once. All at once could block your oil pickup and for sure will clog that oil filter faster and cause the bypass to kick in which will allow unfiltered oil to circulate. When you do run synthetic oil on a high milage engine you really need to check the dipstick more often, if you cannot read the hash marks on it it is time to change the filter.
JMO
Oh, I also only use Mopar coolant, I have noted that some here have used other brands and have had pump failures fairly quickly. Could be that the Mopar specs are of a slightly higher requirement than 'straight off the shelf at the mart' coolant.

K&N air filter

One note on that, I have been running a K&N for a few years. Some one commented on them not doing a good job and mentioned the amount of dirt that was inside the air tube between the filter box and the throttle body.
So I checked and sure enough that tube was filthy. I swap between K&N and stock mopars because I usually let the K&N dry out for a few days after cleaning plus I had bought a case of them when I picked up the jeep new in dec 97 as well as a case of mopar oil filters and a factory service manual. This time I cleaned the tube out and have been running a paper mopar filter for a couple of months to see if the dirt comes back. The jury is still out in my book. When it comes change time again I'll put the newly cleaned and oiled K&N back in and see what happens.

Before you do all that work on your cooling system again replace the fan clutch for the mechanical cooling fan. After about 5 years they can be dead. I doubt it has been replaced.

There is not good way to test the fan clutch. Try to buy one that is idential is size and form as the one you are removing. I found the one for my XJ at carquest. The Autozone one was too large and required me to tilt the radiator forward to install it - not for me.

Since you are unsure of stuff then while you are doing the cooling fan I'd change the fan belt. While you have the fan belt off spin the water pump and the idler pulley to see if they are rough. Might want to replace the idle pulley just as insurance. I'd wait on the water pump until you are more confident on repairs, like the following weekend

If the fan clutch does not do it then condider the flush option.

The water pump has already been replaced. It was starting to leak out of the weep hole. I think the fan clutch is okay going by the hot-cold resitance test i read about. I've already flushed it and i am going to replace the radiator with a more efficient 3 core design. I would put an electric cooling fan conversion in it if it were not such a PITA. Thanks again for all the responses keep em coming.

ATL XJ,

People have discussed at length on here and the conclusion is the tests for those fan clutches "sometimes" work. Which means you get false results.

Since it is a new vehicle to you I'd replace the fan clutch and remove that unknown.

In 2000 I broke the fan belt and over heated my XJ on a cold January night. Sitting at a stop light did not help matters. Anyway I began to run hot after that.

I ended up doing a complete cooling system renewal, radiator, hoses, thermostat, radiator cap, and fan clutch. It looked like the hoses and radiator were 12 years old, maybe the upper radiator hose had been replaced.

I had worked under my engine quite a bit before the day I changed the fan clutch. I got the fan reinstalled on the engine. I started the engine and I went to lay my hand on the AC compressor as I looked under the hood. I had not even laid my hand on the compressor when I pulled my hand away. I figured out what was different, I had felt a strong breeze from the fan, something I had not felt before.

I strongly encourage you to buy a new fan clutch for your cooling system. Also make sure you plugged the electric fan back into the chassis harness. If you are running AC this will make a difference - don't ask me how I know

You know you are probably right, when I run my ac it runs a lot cooler. The electric fan runs with the a/c on. Thanks man. How much do they run for a new one?

RichP said:

The second method is a more gradual method, the 7 hour flush is one where you drain the system, refill with water and put the flush in then drive it for a total period of 7 hours. Does not have to be continous, can be 3 hours one day and 4 hours another but this method breaks the build up down in kind of the reverse order it formed in.

Click to expand...

What product do you use? Brand, name? Thanks Rich,

Tom

ATL XJ,

I paid $43 for the fan clutch in 2000 at my local CarQuest store so figure $50 for a good one.

AC Delco was the mfg of the clutch I removed. I think the dealer was more for this but but they are always an option. You will find on certain parts the dealer is competitive with the aftermarket parts stores.

You will have to remove the shroud and the fan at the same time. It is impossible without breaking the shroud to remove it while the fan is still installed. I think I used a 1/2" combination wrench, took my time and got the 4 nuts off.

Thanks a lot Martin. I think I'm going to change it out. I also think I am still gong to change the radiator since everyone tells me the stockers are crap and need to be replaced after a while. I deal with a LOT of traffic so i think its probably a good idea. Also, it is my understanding that if the 4.0L overheats its done.