buck_hunter Posted January 4, 2012 Share Posted January 4, 2012 don't really know how to put this so here it goes. Just got my truck on the road, and now I'm working the bugs out since it hasnt been ran in over 6 years. When I'm driving, no matter what gear I'm in, when i hit a certian low end on my rpm's it seems to have almost no power almost like its not getting fuel at that point. Once i get my rpms up just a little bit she'll pick up and go. Its just that one area. idk if any of that makes sense lol but i have put a new fuel pump and fuel filter on it. Any help would be nice thanks! Link to comment Share on other sites More sharing options...
txjeeptx Posted January 4, 2012 Share Posted January 4, 2012 Check the intake/exhaust manifold bolts to make sure they're tight. Sounds like a vacuum leak might be causin yer problem. Also look for broken plastic vacuum lines. Link to comment Share on other sites More sharing options...
Pete M Posted January 4, 2012 Share Posted January 4, 2012 the fuel isn't 6 years old, is it? Link to comment Share on other sites More sharing options...
buck_hunter Posted January 4, 2012 Author Share Posted January 4, 2012 nope fuel is good as well. actually just put some higher octane in it since it has been a while that its been ran. Link to comment Share on other sites More sharing options...
mkbruin Posted January 4, 2012 Share Posted January 4, 2012 nope fuel is good as well. actually just put some higher octane in it since it has been a while that its been ran. Seafoam the crankcase and the intake. Replace all plugs/wires/distcap. Oil change. Seafoam in the gas tank (2nd best. Best is to drop and drain the tank, start over). Link to comment Share on other sites More sharing options...
txjeeptx Posted January 5, 2012 Share Posted January 5, 2012 Hmmm, you know that the octane rating is about preventing detonation, so the higher the octane rating, the slower the fuel burns (a flame front/moderate pressure wave), rather than detonating(an explosion/high pressure wave). High octane is only needed to prevent detonation in higher compression, higher performance engines(think Porsche or Vette). The Jeep engines are tractor engines with low compression, so higher octane fuel does nothing to help them run better. Sometimes higher octane can help prevent pinging in hot operating conditions, but that's about all it'll do for a Jeep. It might even be a detrimental thing in extreme cold conditions, since higher octane fuel is less volatile. Higher octane fuel does have a slightly higher heating value than lower octane fuel, so it does have more energy in it, and can result in better fuel economy. But, it usually just winds up costing you more money for what amounts to a performance placebo - you think it runs better, so to you it does, but its all in yer head. If the extra cost at the pump makes you feel like your engine will run better, then I guess its money well spent, but a Jeep engine doesn't need high octane and usually doesn't benefit any from it. My fuel-nerd rant aside, there are some other places to look for problems, but my bet is still on a vacuum leak. One other place I'd look is to check that the TPS doesn't have a dead spot in it, where it goes from sending a signal related to the throttle position to having an open circuit in one spot. That would confuse the heck outta the EFI computer. I also have had problems with MAP sensors with low signal output, where the sensor works, its just not in the range the computer expects to see. Could also have gummed up injectors, if you're MPI. My MJ really liked its fresh set of injectors, made it idle smoother, accelerate better. Finally, the EGR might be coming open too quickly. One other thing - if the spark plugs are gapped too much or old and worn(rounded), the coil might have no problem at idle but struggle when trying to accelerate the engine. Ha, I didn't even bother to ask what engine you have. '87 means at least it won't be the carb'd 2.8. Link to comment Share on other sites More sharing options...
buck_hunter Posted January 5, 2012 Author Share Posted January 5, 2012 I realize higher octane is kind of a waste of money. Thats why the first tank i put in was higher octane but now I'm running just regular but still haveing the same problem. I will definatly check the TPS though that sounds like it might be the root of it all. And if you don't mind me asking who did you go though to get your new injectors because i think that may be some of the problem but i don't want junk ones. So if you have any suggestions on where to get a new set, that would be real helpful. thanks for the advise, i will also be checking for vaccuum leaks. Anybody know the eaisest way to find a vaccuum leak??? and also it is a 4.0. Link to comment Share on other sites More sharing options...
txjeeptx Posted January 6, 2012 Share Posted January 6, 2012 You can test for intake manifold-to-head leaks with any carb cleaner that makes the engine stumble when sprayed directly into the throttle body. It'll make the engine stumble when/if you find a leaky intake gasket. I got my injectors from a local SATX company Fuel Injection Specialties, http://www.fuelinjection.com/. I ordered a set of ACCEL Ford-style injectors through them, but went with stock 19 lb/hr, since I don't have a cam or bigger TB, or free flowing exhaust. My engine is stock. The Ford style injectors have a different spray pattern than the stock Seimens - 4 tiny holes in the spray nozzle instead of one. The set of injectors was about $250 if I recall, so not cheap. Link to comment Share on other sites More sharing options...
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