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Unread 03-31-2013, 06:47 PM   #1
njyj609
Junior Member
1989 YJ Wrangler 
 
Join Date: Feb 2013
Location: capemay, n.j.
Posts: 30
high performance 4cyl?

I bought my 89yj about 4 months ago , my first Jeep.... I thought I wanted more power but after reading several threads on this forum about how much of a dog the 4cyl is, I am now wondering If my 2.5 has been modified previously.... the guy I bought it from had absolutely zero knowledge of the Jeep as he had just bought it himself, and I have noticed while working on the Jeep that all the engine gaskets are new& it is obvious that whoever was the previous owner was a good, meticulous mechanic .

my question is this: my yj does 10mph in 1st , 30in 2nd, 45 in 3rd , and easily 65mph in 4th gear, I routinely do 75mph in 5th gear& could go 85 I'm sure but would be a bit scary I think..... i can accelerate up hill in 4th gear.....is this normal for the 4cyl?...

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Unread 03-31-2013, 06:51 PM   #2
flea1987
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2001 TJ Wrangler 
 
Join Date: Mar 2013
Location: temple, tx
Posts: 143
I'd like to know whats been done to it if you find out, Mine struggles uphill in 4th and 5th
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Unread 03-31-2013, 06:52 PM   #3
flea1987
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2001 TJ Wrangler 
 
Join Date: Mar 2013
Location: temple, tx
Posts: 143
check and see if your axles have tags identifying the internal gears
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Unread 03-31-2013, 07:21 PM   #4
njyj609
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1989 YJ Wrangler 
 
Join Date: Feb 2013
Location: capemay, n.j.
Posts: 30
I will check & get back to you ,but I've been under the Jeep many times....... seems stock , although it may have been re-geared possibly, I do suspect that If it is stronger than usual for a 4cyl Jeep it is probably the engine ..... I'm just not sure If this performance is unusual ......it's not a speed demon by any measure, but it is quite capable.... I can actually get the holeshot at a stoplight If I get on it a bit.... ha
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Unread 03-31-2013, 07:47 PM   #5
4.7stroker
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1988 YJ Wrangler 
 
Join Date: Apr 2007
Location: Rio Rancho NM
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Probably geared, the little 4 has almost 0 afteremarket support that will really give you extra power.

Dwayne
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Unread 03-31-2013, 07:52 PM   #6
flea1987
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2001 TJ Wrangler 
 
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Location: temple, tx
Posts: 143
What gears would help with the acceleration? Mine does ok in 123, but in 4&5 it's a little slow to pick up and go, but it will do 85, barely. Have you calculated mpg yet?
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Unread 03-31-2013, 08:27 PM   #7
njyj609
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1989 YJ Wrangler 
 
Join Date: Feb 2013
Location: capemay, n.j.
Posts: 30
Not sure If your MPG question was to me or Dwayne but I average about 15mpg..... the idea that my Jeep has been re-geared seems reasonable except that
1: it has much torque in low gears
2: the drivetrain was rusty& neglected( ujoints all shot, bolts rusty& original, gaskets all appear to be old)..... at the same time, the engine is fresh, clean & well maintained....idk...... mabey this is common performance for a fresh 4cyl?
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Unread 04-01-2013, 09:19 AM   #8
Que89YJ
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1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
Posts: 13,702
I could push my 2.5L heap to 80 stock with the 29" tires and a good tail wind. There is nothing that I know of that someone would do to make the engine perform better. The 2.5L is a good engine but just runs out of juice fast.
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Unread 04-01-2013, 09:30 AM   #9
soonermatt
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1994 YJ Wrangler 
 
Join Date: Feb 2009
Location: Norman, OK
Posts: 1,396
Your experience isn't too far off from what I get in my YJ on 35s.

I can accelerate to 70mph in 4th gear up hill if I want. I can push 5th to 85 in some situations.

My 4 cylinder was rebuilt 8 years ago and I keep it code free geared correctly.

I think most people who complain about the 4cylinder's power aren't giving it a fighting chance by allowing vacuum leaks and bad sensors, cap and plugs.
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Unread 04-01-2013, 09:40 AM   #10
EABiker
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1989 YJ Wrangler 
 
Join Date: Dec 2004
Location: Frederick, MD
Posts: 1,665
Maybe the previous owner put in a speedo gear for 32" tires instead of one for 31's! Actually, I did that when I first got mine; the speedo always read higher than what I was really doing, but it felt good. Mine seems to be inline with the performance of yours; I have a Jasper engine with 30K on it with all good lines, sensors and gaskets. As you said, no speed demon, but it gets the job done with a lesson on humility now and then!
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