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Old 04-03-2012, 02:12 PM   #1
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Lack of power in my 2.5 sport

Hi all, i've had my 1999 2.5 sport 4 weeks, off road its great but on the road it struggles with slopes 2nd gear needed for slopes my 1.6 fiat stilo could do in 4th!! exhaust is blowing on the manifold would that make much difference? plus exhaust rattles, and it only does 18 mpg!!!
Help.

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Old 04-03-2012, 02:17 PM   #2
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Jeeps are heavy. 4cyl Jeep engines are weak.

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Old 04-03-2012, 02:20 PM   #3
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MPG is typical...not going to see much better then that.

Get your exhaust manifold fixed/replaced.

What size tires do you have and what is your gearing ratio? Many times a previous owner may have installed larger diameter tires without regearing the axles. This will make 'em sluggish on hills...especially the 4cyl.
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Old 04-03-2012, 02:25 PM   #4
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No idea on the gear ratio, previous owner drove it to Portugal last year apparently, standard size 15's, only 58k miles, thought it would have more go in it.
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Old 04-03-2012, 02:29 PM   #5
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Looking at the manifold it looks like there is a stud missing!!! should I be able to see 2 studs/nuts at the fan end of the block??
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Old 04-03-2012, 02:52 PM   #6
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Quote:
Originally Posted by flyingmythos View Post
Looking at the manifold it looks like there is a stud missing!!! should I be able to see 2 studs/nuts at the fan end of the block??
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Old 04-03-2012, 03:04 PM   #7
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Only gets 18mpg? Consider yourself lucky.


What size are your tires? That could be a problem. You said you have standard size 15s? Does that mean stock tires? What does it say on the actual tire, numbers and everything.

My 2.4l with stock tires (28 or 29'' I believe) never had a problem with power on the street, in relation to it being a Jeep. Now with 31'' tires it does lack some power, but not enough to make me worry.

You have to realize, the fiat is probably half the weight of the Jeep. These vehicles (Jeeps) arent built for speed.
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Old 04-03-2012, 03:30 PM   #8
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225/75 15 tyres, looking at the manifold pic I seem to be okay as it looks like there isn't any bolts missing, best try to get a manifold gasket in the UK then, thanks for your help guys.
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Old 04-10-2012, 04:23 PM   #9
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I removed the manifold today, 5 bolts only? is that correct? and noe gasket on the exhaust, only intake gasket, should there be a gasket for the exhaust as it was just metal on metal?
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Old 04-11-2012, 02:09 PM   #10
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2 studs are snapped by previous owner (idiot) and I can't drill them out with my DIY tools so new gasket is on and I am about to try to fire the jeep up, good luck to me as this the 1st time I have done anything like this, who knows? it might work!!!!!
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Old 04-11-2012, 06:22 PM   #11
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The 4 cylinder jeeps are just weak! I had one and the motor finally went and I rebuilt it and did all I could to get more power and it was still pitiful all you can do is gear it for the lost power! I have a 6 cylinder now and its night and day difference
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Old 04-11-2012, 08:25 PM   #12
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well 4 bangers are not for runnig or towing heavy stuff i have a 98, but i put some extras and every hp u can free of that engine is very usefull.
i have a hiflow air filter +2-4 hp (i think)
hi flow catback +2-4
8mm spark wires+1-2
and it runs well lack of power but nice mpg im getting in city like 18- hwy20-21 on 31´s
so be happy 4 bangers are very good u have to love it to understand it =D
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Old 04-12-2012, 10:38 AM   #13
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I am about to build a '98 4-banger I bought to put into my '97. Got it for a song and have been building engines for four decades. I plan on documenting the build...hopefully can do some justice to this anemic power plant. Gonna start with GOOD pistons to cure the inherent "piston slap" issue the factory decided to live with. Second...mill and rework the cylinder head...where power is actually made. Then...a better camshaft. Probably the 4.0 TB just for kicks.
Any input appreciated...getting started here soon. Wish me luck! Ron
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Old 04-12-2012, 12:30 PM   #14
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Quote:
Originally Posted by flyingmythos View Post
I removed the manifold today, 5 bolts only? is that correct? and noe gasket on the exhaust, only intake gasket, should there be a gasket for the exhaust as it was just metal on metal?
From the factory there is no gasket.

Quote:
Originally Posted by flyingmythos View Post
2 studs are snapped by previous owner (idiot) and I can't drill them out with my DIY tools so new gasket is on and I am about to try to fire the jeep up, good luck to me as this the 1st time I have done anything like this, who knows? it might work!!!!!
Replace the studs any way you can, mostly they will come out with a good set of special tools. If or when the manifold warps you have more trouble on your hands.

Quote:
Originally Posted by Ron Lee View Post
Any input appreciated...getting started here soon. Wish me luck! Ron
Good luck. I doubt you will get a lot more power from this engine. Looking at the overall design it could have been build in the 50's. Maybe it was.

Anyway, here's a pic of the head, not a lot you can do, maybe bit bigger exhaust valve, shave some more off to up compresion somewhat. Maybe you can use the stroker technology on the 4 banger idunno...that would be good..2.7 stroker LOL.

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Old 04-13-2012, 12:32 PM   #15
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Hello again, the jeep sounds much better and fuel cosuption is up, however it wont rev past 3500??? it will whilst not in gear but when driving it won't fully rev, fuel starvation?? its had new rotor arm, cap leads and plugs, and ideas???
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Old 04-14-2012, 09:34 AM   #16
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Are you saying 18mpg or kpg since you're driving in Europe? I'd kill to average 15mpg on my 10.5 x31 x15's
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Old 04-15-2012, 10:36 AM   #17
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my TJ is working great now, don't know what I did but went from only revving to 3500 to full revs so I have stuck on a max flow air filter and it is better than ever before, now I know the engine is good it's time for some big wheels or oversized tyres, thanks for the advice guys.
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Old 04-15-2012, 10:49 AM   #18
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I just purchased a 97 wrangler 2.5 with new fuel pump and am concerned with lack of power. Top end is probably around 70 MPH with 31x 1050 x 15 tires. I don't know what gear ratio is. Also have a concern with oil pressure. Has a new oil pump and gauges goes to 0 at hot idle and gauges light come on. I was told they had put a manual gauge on it and oil pressure was fine but I hate that red gauges light coming on. Any suggestions.
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Old 04-15-2012, 12:29 PM   #19
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to the OP. deeper. gearing.
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Old 04-15-2012, 12:48 PM   #20
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Quote:
Originally Posted by flyingmythos View Post
Hi all, i've had my 1999 2.5 sport 4 weeks,
Before anyone thinks there is such a thing as a 2.5 Sport model, I assure you there is not. All TJs with 2.5 liter motors are designated as "SE" (Special Edition). All of the "Sport" models came with 4.0s in them.
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Old 04-15-2012, 01:48 PM   #21
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Quote:
Originally Posted by Ron Lee
I am about to build a '98 4-banger I bought to put into my '97. Got it for a song and have been building engines for four decades. I plan on documenting the build...hopefully can do some justice to this anemic power plant. Gonna start with GOOD pistons to cure the inherent "piston slap" issue the factory decided to live with. Second...mill and rework the cylinder head...where power is actually made. Then...a better camshaft. Probably the 4.0 TB just for kicks.
Any input appreciated...getting started here soon. Wish me luck! Ron
PLEASE let me know if you find a better camshaft. I would love to replace the stock cam with something better but only option I found was to have one custom ground.
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Old 04-15-2012, 02:00 PM   #22
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Quote:
Originally Posted by Border Dave View Post
Before anyone thinks there is such a thing as a 2.5 Sport model, I assure you there is not. All TJs with 2.5 liter motors are designated as "SE" (Special Edition). All of the "Sport" models came with 4.0s in them.
actually there were. in europe they were called 2.5L sports.
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Old 04-15-2012, 02:44 PM   #23
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actually there were. in europe they were called 2.5L sports.
Thanks. I learned something new.
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Old 04-28-2012, 06:50 AM   #24
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I learned that Jeep sold the gas engines in Europe. I thought that everyone there had diesel engines in their Wranglers.
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Old 04-28-2012, 07:44 PM   #25
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I get about 18 mpg with mine. Only have an intake and tb spacer. How much hp gain would I get from an elect fan and larger plug wires? And from those who have done it is it worth the cash to do the fan?
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Old 04-28-2012, 09:21 PM   #26
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I have a 98 with a 2.5, I have 33" Tires and just installed 4.88 gears. now my speedo is accurate and my power is great for a 4 banger. I get between 15 and 17 MPG.
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Old 04-28-2012, 10:08 PM   #27
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Quote:
Originally Posted by Wildtaco
I have a 98 with a 2.5, I have 33" Tires and just installed 4.88 gears. now my speedo is accurate and my power is great for a 4 banger. I get between 15 and 17 MPG.
How do you change the speedo gear?
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Old 04-28-2012, 10:13 PM   #28
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Quote:
Originally Posted by stuckinwater

How do you change the speedo gear?
Remove the vss from the transfer case, it's held in with one bolt and a collar bracket, pull the gear off, put the new gear on, reinstall. Depending on how much lift you have you don't even need to jack up the Jeep to get under.. Should take like 3 minutes to do
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Old 04-28-2012, 10:18 PM   #29
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Quote:
Originally Posted by darkproximity

Remove the vss from the transfer case, it's held in with one bolt and a collar bracket, pull the gear off, put the new gear on, reinstall. Depending on how much lift you have you don't even need to jack up the Jeep to get under.. Should take like 3 minutes to do
Ok! Thank you!
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Old 04-28-2012, 10:18 PM   #30
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Quote:
Originally Posted by SledNeck600
I get about 18 mpg with mine. Only have an intake and tb spacer. How much hp gain would I get from an elect fan and larger plug wires? And from those who have done it is it worth the cash to do the fan?
They make throttle body spacers for the 2.5??

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