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Unread 03-31-2013, 03:22 PM   #1
flea1987
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Wrangler milage/power

So, I know this is a pretty common question being asked, and I see a lot of people get picked on for it.

I have a 1990 Wrangler and I'm trying to find out what engine I can put in it (it's a stock straight 4 and a 5 speed tranny) and keep as much stock as possible and slightly improve gas mileage and power.

I know it will never get great gas mileage, but it has no lift and I have the recommended tires on it as well.

Thanks.

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Unread 03-31-2013, 04:20 PM   #2
Louie4
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A High Output 4.0L?

That will be as close to stock as you can get if you want to improve what you have. Why not just get a 2.5L from a newer model? Or rebuild the 2.5L if you're not planning to keep it stock?
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Unread 03-31-2013, 04:40 PM   #3
flea1987
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With the current motor I'm magically pulling off 19mpg.... stock, top end is rebuilt but needs new... not sure what they're called, but they have lines connected to them on the valve cover and a new oil cap, as it spits oil out of the top right now.. lol. However, If it's getting 19 (all my driving has been highway so far) I figure it can do better with a motor with a little more power. A newer engine would need a brain though correct? (fuel injection)
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Unread 03-31-2013, 05:47 PM   #4
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Quote:
Originally Posted by flea1987 View Post
With the current motor I'm magically pulling off 19mpg.... stock, top end is rebuilt but needs new... not sure what they're called, but they have lines connected to them on the valve cover and a new oil cap, as it spits oil out of the top right now.. lol. However, If it's getting 19 (all my driving has been highway so far) I figure it can do better with a motor with a little more power. A newer engine would need a brain though correct? (fuel injection)
Yes you would need the wiring and ECU and all that. It sounds like your crankcase ventilation system is plugged and pushing the oil back through the fresh air inlet. Check all those lines, the manifold port, and the valve cover to see if there is a lot of crud built up. I had the same issue. I ended up taking my valve cover off, removing the baffles under it and cleaning them thoroughly. Haven't had the issue since.
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Unread 03-31-2013, 05:52 PM   #5
flea1987
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They're pretty loose, don't know what they're called and local parts store guy got confused when I pointed them out, they're loose and when idling you can watch the oil splash out. Need to know what they're called so I can buy new ones and see if it fixes the problem.
engine-top-edit.jpg  
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Unread 03-31-2013, 07:27 PM   #6
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How hard is the fuel injection swap?
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Unread 03-31-2013, 07:45 PM   #7
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The 4 banger has FI

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Unread 03-31-2013, 08:38 PM   #8
flea1987
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Mines carb
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Unread 03-31-2013, 09:29 PM   #9
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Those are PCV (Positive crankcase ventilation) valves. It's probably throttle body injection.
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Unread 03-31-2013, 09:44 PM   #10
flea1987
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Just got it recently, I'll check when I get back from offshore.
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Unread 03-31-2013, 11:02 PM   #11
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I don't see a fuel rail in the picture like on a fuel injested but I may just be blind. Just to make sure you do have an electric fan correct? Just asking bc I can't see one behind the rad
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Unread 04-01-2013, 08:48 AM   #12
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X2 on the fan. The other issue is you're missing a stud and nut on the water pump pulley.
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Unread 04-01-2013, 09:25 AM   #13
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Quote:
Originally Posted by flea1987 View Post
They're pretty loose, don't know what they're called and local parts store guy got confused when I pointed them out, they're loose and when idling you can watch the oil splash out. Need to know what they're called so I can buy new ones and see if it fixes the problem.
If this is your engine, then you are already Fuel Injected. ALL YJ 2.5L models are FI from the factory. The 1987-1990 models are Throttle body Injection (TBI), which means they have a throttle body and one big injector inside of the throttle body. It's a crude form of FI, but it avoids the additional costs with a more modern style FI system.

Which brings us to 1991-1995 YJ 2.5L models, which are Multi-Port Fuel Injection (MPFI), and have one injector per cylinder (4 total). Pop the air cleaner off of the throttle body and you will see a big injector in there.

Swapping to an MPFI setup is not worth the time or effort for a mere 3HP power gain, and nearly 0mpg gain. You have to swap mostly everything electrical on the Jeep (computer, harness, fuse panel, so on and so forth).

As for your circles, the circle ontop is a Crankcase Ventilation Breather (dealer only part, it's about $12), and the part on bottom is your PCV valve. You will likely have to replace both of the grommets.

------------

As far as MPG goes, 19mpg average is absolutely fantastic with our glorified bricks. You won't be getting much better, not without careful highway driving and possibly a bigger engine.

Stock vs stock, the 2.5L Jeeps do better on gas both on the road and on the trail than the 4.0L models.
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Unread 04-01-2013, 10:30 AM   #14
flea1987
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This is not my engine, lol I have a clutch fan and a GIANT fan shroud lol. I'll put an actual picture up when I get back from offshore, who knows when that'll be with the BOP acting up
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Unread 04-01-2013, 11:14 AM   #15
Siva283
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Quote:
Originally Posted by Xpress View Post
If this is your engine, then you are already Fuel Injected. ALL YJ 2.5L models are FI from the factory. The 1987-1990 models are Throttle body Injection (TBI), which means they have a throttle body and one big injector inside of the throttle body. It's a crude form of FI, but it avoids the additional costs with a more modern style FI system.

Which brings us to 1991-1995 YJ 2.5L models, which are Multi-Port Fuel Injection (MPFI), and have one injector per cylinder (4 total). Pop the air cleaner off of the throttle body and you will see a big injector in there.

Swapping to an MPFI setup is not worth the time or effort for a mere 3HP power gain, and nearly 0mpg gain. You have to swap mostly everything electrical on the Jeep (computer, harness, fuse panel, so on and so forth).

As for your circles, the circle ontop is a Crankcase Ventilation Breather (dealer only part, it's about $12), and the part on bottom is your PCV valve. You will likely have to replace both of the grommets.

------------

As far as MPG goes, 19mpg average is absolutely fantastic with our glorified bricks. You won't be getting much better, not without careful highway driving and possibly a bigger engine.

Stock vs stock, the 2.5L Jeeps do better on gas both on the road and on the trail than the 4.0L models.
Going to MPFI gives you about 30 more horsepower. Not just 3. Que89yj is getting ready to do it. I just sent him the parts from my old engine. He wouldnt do it just for 3 horsepower. Also with MPFI and 33x12.5 tires I am still getting about 17mpg on stock gears.
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