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Old 01-09-2012, 01:46 AM   #1
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Acceleration Problems

Have a 94 S with the AMC 256 4 cyl in it and I am having some trouble accelerating and cruising. I just had the head gasket redone on it and the water pump replaced. I also have it on a Rough Country 4" Lift with 32"x11.5"x15" Goodyear Wrangler MTR w/ Kevlar. My issue comes when I shift into 4th gear. I can accelerate all the way through 3rd but when I shift into 4th I have no power at all. I can have the pedal pushed all the way to the floor and the speedometer drops like a rocket. I am going to check the timing soon but if anyone has any other ideas I am all ears... I love my Jeep and miss driving it, but I am stumped as well as most of the people that I know. Thanks for any ideas and help.

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Old 01-09-2012, 01:53 AM   #2
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How long have you had the 32" tires on it? Also, what else has changed since it drove the way you wanted it too?

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Old 01-09-2012, 01:59 AM   #3
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you sure its the AMC 256? or are you meaning the AMC 150?

The 150 is the 2.5L 4Cyl
The AMC 242 was the 6Cyl that year..
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Old 01-09-2012, 03:02 AM   #4
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When is the last time you changed the fuel filter? I had a 5 year old gmc pickup that did the same thing...would flatten out with no power up at 50-55 mph.The engine was starving for fuel with a restricted fuel filter.
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Old 01-09-2012, 06:43 AM   #5
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I was told it was an AMC 256 because it is a 94 Wrangler S. I have recently had the fuel filter changed as well.
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Old 01-09-2012, 07:01 AM   #6
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Did a little digging and it is the AMC 150. With that out there any ideas?
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Old 01-09-2012, 07:05 AM   #7
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Quote:
Originally Posted by The Toolman
How long have you had the 32" tires on it? Also, what else has changed since it drove the way you wanted it too?
I bought it with 32" tires. But I added a lift since I bought it. But I was having that problem in 5th when I bought it. I could cruise in 4th but in 5th I would decelerate even with the pedal pushed to the floor.
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Old 01-09-2012, 08:07 AM   #8
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Timing can play a Big part when it comes to power, or the lack of power.
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Old 01-09-2012, 08:16 AM   #9
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Just a shot in the dark... but I ran into the same issue where a ranger would top end at 50mph no matter what. Turned out to be a bunch of leaves packed into the air box under the filter from critters. Urgg.... the back tires also had leaks and were dragging its ass at 20 pounds and 25 pounds. The third thing I found was the rear brakes had a leaky wheel cylinder and everything got gummed up on the right side and was dragging it. All in all, I re-did the rear brakes and aired up the back tires. Then, it had a lot of HP back and rode better but shoot, it still topped out at 50. It wasn't until I got the leaves out of the air box that it got better. Took 'er up to 70mph no prob.

Maybe your air filter is clogged up?
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Old 01-09-2012, 08:36 AM   #10
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Have had the air filter all the way off and cleaned it out and the tires are brand new. But I may look into the rear wheels being gummed up.
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Old 01-09-2012, 12:56 PM   #11
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With the lift and large tires I don't think you will get it any better. 4 bangers are not known for their cruising power. You might get a little more out of it with a tune up and 02 sensor. Who did the head work? You might have a problem there. Timing is set by the computer..... Was a new timing chain installed? Distributor pulled?
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Old 01-09-2012, 01:36 PM   #12
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Tune it up and it will do better... But without re-gearing to 4.56 with those tires you won't be able to use 5th gear anywhere but on a long slightly down sloped section of hill.

Do yourself a FULL tuneup.

Distributor Cap
Rotor
Plug wires (all 5 of them, including the one from coil to dizzy)
Plugs
Air Filter
Fuel Filter
Fuel Injector Cleaner
Thermostat
Oil Change kit
Coolant (should be replaced every 2 years or so)

The last 3 won't do much to help performance, but it will keep the engine running happy. And if your coil is stock, might want to replace it.

One more thing... since your Jeep is a 1994 MPFI model, you have lots of potential to get more power out of it... Some people have seen as much as 45hp with some upgrades like injectors, high flow intake, 4.0 TB, TB spacer, exhaust, things like that. Something as simple as dropping the engine driven fan and upgrading to an electric fan can net as much as 8hp.
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Old 01-09-2012, 03:25 PM   #13
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Quote:
Originally Posted by Xpress
Tune it up and it will do better... But without re-gearing to 4.56 with those tires you won't be able to use 5th gear anywhere but on a long slightly down sloped section of hill.

Do yourself a FULL tuneup.

Distributor Cap
Rotor
Plug wires (all 5 of them, including the one from coil to dizzy)
Plugs
Air Filter
Fuel Filter
Fuel Injector Cleaner
Thermostat
Oil Change kit
Coolant (should be replaced every 2 years or so)

The last 3 won't do much to help performance, but it will keep the engine running happy. And if your coil is stock, might want to replace it.

One more thing... since your Jeep is a 1994 MPFI model, you have lots of potential to get more power out of it... Some people have seen as much as 45hp with some upgrades like injectors, high flow intake, 4.0 TB, TB spacer, exhaust, things like that. Something as simple as dropping the engine driven fan and upgrading to an electric fan can net as much as 8hp.
I will check into doing some of that... I have already done some of those things. I will check into regearing too.
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Old 02-20-2012, 02:09 PM   #14
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You mentioned head gasket replacment.....I guess my red flag on that is did you overheat it? Could there be engine damage? Maybe a compression test would be in order. I'm guessing you lost 4th gear power after the head gasket? you where not clear on that.
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Old 02-20-2012, 11:20 PM   #15
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If you had to replace the head gasket... Did you take the head to a shop to have it checked? At the very least it needs to be checked for perfect flatness. The safest thing to do would be to get it resurfaced and have the valves re-done.
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Old 02-21-2012, 01:05 PM   #16
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Quote:
Originally Posted by Xpress View Post
If you had to replace the head gasket... Did you take the head to a shop to have it checked? At the very least it needs to be checked for perfect flatness. The safest thing to do would be to get it resurfaced and have the valves re-done.
Yes I agree. This is what I meant by engine damage. Uneven head. Or maybe piston ring or cylinder damage. Any of which could cause low compression and this problen your having.

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