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11-18-2008, 09:12 AM
| | |  Yj 2.5 Wont Accelerate!
Hi guys, I have a '90 2.5 yj 5-spd and it wont accelerate enough for me to even shift into second gear. I've replaced the O-2 sensor, and checked the fuel pump. Could it be a vacuum problem? Or EGR valve? Thanks for your help.
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11-18-2008, 09:44 AM
| | Way Outta Control | | Join Date: Sep 1999 Location: The Palouse
Posts: 13,158
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How did you check the fuel pump? There's no way I know of to test the pump under load on the road. Did this problem crop up suddenly? Were any other changes made when it started? Did you check the backpressre at the tailpipe? Could the cat converter be plugged? Is the exhaust restricted. If you lift the hood at night, after running the engine does the cat converter or the exhaust manifold glow a dull to bright red? Have you check the MAP sensor?
Could it be a vacuum problem? Not likely, but have you checked the vacuum? If so, what are the readings?
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11-18-2008, 10:02 AM
| | | Map sensor
I think the vacuum was 20in, no cat, no exhaust restrictions, how can I check the MAP sensor?
Thanks,
Paul
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11-18-2008, 10:23 AM
| | Way Outta Control | | Join Date: Sep 1999 Location: The Palouse
Posts: 13,158
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MAP is checked via voltage
What is the fuel pressure?
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11-18-2008, 06:02 PM
|  | Keyboard Implanted | | Join Date: Jun 2000 Location: Southeastern Indiana
Posts: 4,634
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I am tossing my guess in for fuel pump. I had a similar problem with my TJ.
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11-21-2008, 02:19 AM
| | Aprentice | | Join Date: Oct 2008 Location: near Seattle
Posts: 95
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Did you recently take out the cat? Pieces of it may have fallen into the muffler to await the "right" time to cork the exhaust and slow your Jeep down. Pull out the O2 sensor and see if the power picks up,
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11-21-2008, 03:06 AM
| | Way Outta Control | | Join Date: Sep 1999 Location: usa
Posts: 10,698
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When it won't accelerate, what does it do? Does it backfire? if so, out the top or out the exhaust?
Groan loudly?
Just run normal but won't speed up?
More info would be helpful.
Check the color of the spark - red and hissy? A snappy bright blue?Check it at a plug and check it right at the coil. It should be the snappy blue if the ignition is OK.
After you try it with the o2 sensor removed, try the propane trick to see if it's a lack of fuel. Search here for "propane trick," it'll tell you how to make the tester. Add some propane while you try to accelerate, if it "likes it" it's a fuel problem.
Did you, or anybody steam or pressure wash it recently? TPS's don't like it and frequently fail soon after.
Let us know.
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11-21-2008, 06:19 AM
|  | Moderator | | Join Date: Dec 2001 Location: Belleville, Illinois
Posts: 9,616
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A link to the propane trick writeup is in the Welcome post.
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