1991 5.8 running rough
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4wd Low
Joined: Aug 2022
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1991 5.8 running rough
I have a 1991 f250 5 speed with a 5.8 and it’s running pretty rough, it sat for seven years with a bad fuel pump before I bought it. I replaced the fuel pump and it idles pretty rough almost like it has a misfire it has low power and it really struggles to make it to 2k rpm’s let alone past it and the fact the throw out bearing is so loud definitely makes it harder to hear the engine itself. The alternator was bad as well so I replaced that and I ran some sea foam through and it helped the tiniest bit but I’m really at a loss for what to do next, any suggestions y’all?
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4wd Low
Joined: Aug 2022
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I replaced the fuel filter twice and there’s no check engine light, I’ll check fuel pressure today though and let y’all know I’m kinda leaning towards a bad fuel pressure regulator
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4wd Low
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Sorry for the late reply but I got 35 psi off and 40 when it was running so It can’t be the fuel pressure regulator right?
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What are you calling E87 fuel? I hope you didn’t fill it with an 87% ethanol / 13% gas blend. The truck was designed to use 100% gasoline but you can safely use up to 10% ethanol.
I’m pretty sure you cannot do a cylinder balance test on a ‘91. Another possibility it that an injector or multiple injectors have debris in them or aren’t working. We aren’t getting much information from the OP and no actual tests that he has done to pinpoint the problem.
I’m pretty sure you cannot do a cylinder balance test on a ‘91. Another possibility it that an injector or multiple injectors have debris in them or aren’t working. We aren’t getting much information from the OP and no actual tests that he has done to pinpoint the problem.
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4wd Low
Joined: Aug 2022
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Hey guys sorry for responding so late but I think I might have the answer, when I first bought the truck the battery cable colors were switched so I had it hooked up wrong for awhile before I finally figured out what the issue was, So I’m thinking that the battery being hooked up wrong could’ve shorted out the ecu causing it not to run right. Could that be possible y’all or am I 180 degrees in the wrong direction. It would also explain why when I finally got it to start the alternator wasn’t charging and I had to replace it.
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