Topic: How does my 2.5 compare to the norm?

[jcguin]

About a month ago I picked up a 97 TJ 5-speed 2.5 with 167K on it for 4600.  It is pretty much stock, (29 inch tires, no lift) and in really good condition other than the mileage.  I had wanted a jeep since I was 12, and am 42 now.  I love this thing, but I wanted to know how it compares to the rest of it's kin.

It gets 16-18.2 mpg.

It will only do 55 into the wind, or uphill.

Has a little buck to it first thing in the morning taking off (yes I let it warm up) (and yes I know how to drive a stick).

After it sits for a few hours it takes about four seconds to start.  Or you can key it off after a second, then key it back on and it will start instantly.  (fuel lines draining back into tank?)

I had heard somewhere that the catylitic converters should be replaced after 150k because of buildup and blockage, and that could cause a loss of power at higher speeds.  Have ya'll found that to be true?

I'm looking for comparison data.  I typically drive 60 miles a day, of which 30 is highway, 20 is 50mph country roads, and 10 is city.  I dont dog it, I love it too much.

Thanks everyone,

[Jeffy]

16-18mpg isn't bad.  Although for a stock Jeep, it could be a bit higher not not by much.

55mph top speed isn't right.  Even with my poor gearing, I'm able to hit 65mph and when things are favorable 80mph.

It shouldn't buch or sputter or be hard to start.  When  you turn the key ON you should gear a buzz and the fuel pump should pressureize the lines before you even try starting.

Cat's generally last about 7 years or 150K miles.  After that they are no longer covered under the extended emissions warranty and can be legally replaced.  Most blockages are casued by impact with something hard or ig your engine runs rich.  Damage can also occure if you use leaded fuel.

If you think you're lacking power, you might try to do bring up the diagnostic mode and see if any error codes have been triggered.

Follow these steps: http://www.dirtroadmagazine.com/codes.htm

I'd also maybe look ar replacing the fuel filter.  It's possible that it's dirty enough to restrict flow.

[jcguin]

It will do 65-70 on the flat with no headwind, but I doubt 75.

  I'll run the diagnostics codes and see what comes up.  I should probably reset them  and drive it a while first though.  I know he got the engine about 15k ago from a junkyard.  No idea how many miles the engine has,   only what the odometer says on it.  I figure the odometer is right for the catylitic converter though.  I cant imagine him replacing the exhaust when he changed out the engine.

  It does have a slight rattle at the higher rpm's in the area of the converter too.  But not when you tap it.  One other note is the exhaust sounds like it has a hole in it somewhere, but I replaced the muffler and did not see anything there, that was the other reason I was thinking about the converter.  I wish I had someone around me with a 4 banger to compare it to.

  I'll tell you what though, this little 4 will climb a tree with the right tires in 4 low.  

  It's also nice to have an engine you can actually work on again.  My other two vehicles are a 95 z28 and a 2003 Mountaineer.  It cost me a grand to drop the engine in the Z so the back plugs could be reached for change out and tune up.  And with this thing I dont even need to jack it up to change the oil.  What a nice change.

[chrisfranklin]

My '94 YJ4 on 29s runs at 80mph at around 3000RPM, which I kind of consider max cruise RPM.  I'll generally run at 80mph in wide open highway areas.  In the more urbanized areas, I'm generally at about 75mph at around 2700RPM.  

On a flat road, I have topped out at 95MPH with the soft top flappng like crazy (what can I tell you I heard that old story about the Mt. Saint Helen's Volcano eruption back in the 80's:  the folks driving away from the lava flows at 60mph got creamed; the folks doing 100mph made it out alive   I wanted to see if I could maintain 100mph or so; so, I'm just rounding up, I guess  :) Hey, if you are ever trying to get away from a natural disaster.... Before any kind of modification to my YJ4, it was struggling to do 70mph on 205s; and acceleration to that speed was abysmal.  

Will say this though, doing Catback and intake mods are what really opened my Jeep up for higher speed running and easier uphill/headwind operation (can generally accelerate in 5th on moderate upgrades/headwinds  and maintain 75mph to 80mph or faster)

Sounds like you may also have an obstruction somewhere, could be CAT/exhaust/exaust tubing, fuel filter, even intake if you haven't checked that out; crap spark, engine vacuum leaks/exhaust tubing crunched, codes!.

[jackhammer]

My stock YJwill do 75-85, varying due to wind speed . comfortable high way cruising at around 65-70.  where are you located you probebly do have someone by you. You can always stop at a used car lot looking intereasted and go for test drive

[jcguin]

Will say this though, doing Catback and intake mods are what really opened my Jeep up for higher speed running and easier uphill/headwind operation (can generally accelerate in 5th on moderate upgrades/headwinds  and maintain 75mph to 80mph or faster)

What Catback and intake mods would you suggest?  I was expecting to pay more than I did, so I've got some cash set back to take care of a few things.  

One other major plus to owning a Jeep as compared to most other vehicles, that I had not taken into consideration was the availability of parts.  It sure is nice that suppliers have to compete for your money, as opposed to you being at their mercy.  

Oh yeah, and that was a good suggestion jackhammer, I had not considered stopping in for a test drive for comparison.  

Ya'll have a good day and thanks for the input.

[Jeffy]

If you wanted to start moding the engine, I'd start off with an electric fan and a 4.0L TB.

I covered a whole secton on the intake in a recent post so you might want to do some searching.

[jcguin]

Thanks Jeffy, I think I saw your intake post, but I think it was for an earlier model though.  I'll read up on it and see what it will cost and involve.  

I planned on replacing the Cat anyway because of the age and slight rattle.

 Hard to imagine a fan making as much difference as some say.  But reality can be stranger than fiction.

[Jeffy]

Thanks Jeffy, I think I saw your intake post, but I think it was for an earlier model though.  I'll read up on it and see what it will cost and involve.  

I planned on replacing the Cat anyway because of the age and slight rattle.

 Hard to imagine a fan making as much difference as some say.  But reality can be stranger than fiction.

http://www.4bangerjp.com/forums/viewtopic.php?t=442

[jcguin]

Jeffy, by the link are you suggesting a snorkel?  I was figuring a 4.0 tb and porting the intake.

[Jeffy]

Jeffy, by the link are you suggesting a snorkel?  I was figuring a 4.0 tb and porting the intake.

No, go to page 3, I think.  I go through some of the basic's about intake design and function.

[lutzke21]

The leaking sound you're hearing could very well be the exaust manifold.  It is notorious for cracking easily.  You should check there as well.

I too started my love for jeeps at an early age.  Remember the old Sears catalogs with all the CJ bling?  That's where my affair started.  Bought my first YJ 14 years ago, my current YJ 10 years ago.

[jcguin]

lutzke21,  I'll check out the manifold.

As for loving them from an early age.  My love affair started at 12 when I visited my uncle in Alabama who was a retired sgt major.  He had a cj at the time and let me take it anywhere I wanted for the month I was down there, including anywhere on his 150 acre farm. or 10 miles to the store.  One time the Sheriff saw me at the store and said "boy, does sarge know you have his jeep?  You mess it up and he will have your butt"  This was back in 75'.  Cops were different then, especially in the country.  No thought to being old enough to drive.

[BK2LIFE]

my 92 4cyl yj sucks.  it has 31's, and the factory 4:11's.
it has a high flow cat, 2.5 flowmaster exhaust, aftermarket air box/filter, new plugs, wires, cap rotor,fuel filter and i have to downshift to 3rd when goin up any mild hill on the freeway.  5th gear? i havent used 5th gear in years.  im at 3000 rpm in 4th gear is my freeway speed. any wind, or hills and im in 3rd at 3500+ tryin to get back into 4th.  ive got no codes, clean oil, no exhaust leaks, good runnin motor, just has NO power.  im gunna do the 4.0 TB and port match the intake to the TB and to the head.  any one have any ideas?  i was going to try a different engine computer, i doubt it will do anything, but im runnin out of ideas...

[jackhammer]

I am pretty sure that optimum gear for 31s on 4cyl manual is 4.56. I could be mistaken. that should give you 5th gear back.  
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I am waiting to take my first emission test in my YJ, but soon after I am going to do the TB swap everyone here thinks its one of the best cost effective mods you can do on the 4bang.