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Old 08-14-2012, 12:58 AM   #1
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1990 Yj issue. Need advice.

I just bought a 1990 yj this weekend. 2.5l 5 speed with 120,000 miles on her. Pretty darn clean. When I test drive it everything seemed fine, however the owner live so far away from the highway I couldn't see how it would do at higher speeds. I went through all the gears and everything seemed fine. I noticed nothing. The jeep was on E so So I got gas right after 2 full days of rain. I got on the highway and it started to miss or drag intermittently. I immediately thought it was bad gas. I got it home, through a bottle of the iso-heet dry gas stuff in her. Today I got it legal and drove it to work. What is weird is it acts and drives fine in all gears in normal road city driving. Stop to about 55mph. Get on the highway and it still was doing it. Could it still be bad gas? Or a spark, TuneUp and fuel filter issue? Obviously I'm going to start with plugs wires cap and rotor and throw a new fuel filter in it. But what else could this be. I am worried sick because I just bought this thing. Or maybe a Carb adjustment issue. It acts like the more gas I give it the more it wants to lag. So maybe its getting to much fuel for the spark its getting maybe. I haven't pulled any plugs yet to look but I'm sure it needs a TuneUp. The guy that owned it previous never mentioned when he did it last or ever. Any help would be appreciated. Thanks.

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Old 08-14-2012, 01:06 AM   #2
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Sounds like u need a major tune up like ur thinking... Plugs,wires, cap and rotor, maybe ignition control module/ and copasitor, and fuel filter, air filter and check fuel pressure to see if pump is getting weak it does sound like a fuel and spark issue...

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Old 08-14-2012, 01:09 AM   #3
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The 90 2.5 is TBI throttle body injection, No carb.

I would try the tune up that you stated. could be a spark related issue. Or a bad fuel filter.

I wouldnt think that its anything major, or it would be more prominent in the city driving instead of just on the highway.
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Old 08-14-2012, 01:43 AM   #4
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Alright thanks, I'm gonna try and do the fuel filter today since its cheap and maybe throw in a bottle of sea foam for good measure. Ill probably have to wait till pay day this weekend to do the tune up. Ill keep ya posted.
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Old 08-14-2012, 04:57 AM   #5
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What do you guys think could it be the TPS? Could be alot of things I know haha
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Old 08-14-2012, 07:21 AM   #6
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Dont put too much "Miracle in a Bottle" in it. That isnt good either. Do the tune up, check for codes and address those issues.
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Old 08-14-2012, 07:59 AM   #7
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Not tps if it was that the idle would way low or or kinda high... And it would be more notable at lower speeds too....
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Old 08-14-2012, 03:11 PM   #8
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Good luck man, Lotts of people have little issues with these 2.5. They tend to run great for a long time and then wamooo. These 2.5 can be on the tricky side, to find lil gremlins in throtlebody, sensors, dist, fuel issues, CPU could all be cupruts. Firt check for good comp,fuel,spark. Make shure timing is TDC, my 87 has computer controlled fuel and timing. Open the hood at night and make shure theres no arching. Check your fuel presure with a gauge, My 87 is at 15 psi, newer might be differen't. If those all check out look at sensors or possible Vac leaks or cracked exahust manifold or bad gaskets. I have the same problems with my 87 and have done most of what what was said in the above paragraphs and still have a problem. My next thing to replace is the computer CPU. Good luck, the answers will come.

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