F250 5.8 Rough Idle Problem - Ford Truck Enthusiasts Forums

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F250 5.8 Rough Idle Problem

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Old 11-08-2018, 06:33 PM
CustomHD
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F250 5.8 Rough Idle Problem

Got this truck not too long ago, when I got it, it had a check engine light for 2 things, TPS sensor, and another sensor I forget the name of, but is vacuum actuated. After replacing those 2 my check engine light went away but I'm still getting a really rough idle. Too rough to just be engine mounts, but they are definitely getting torn up from the shaking. The ticking that kind of sounds like a misfire is because of a crack in the exhaust manifold, not sure if that could cause an idle this rough by tricking the egr system? Plugs and wires are new as well as all of the normal matenince stuff, only other thing I can think of to replace is injectors but wanted to see if anyone else had this problem before I put money in the wrong places. It's not a surging idle like I've seen some people have with their 5.8's and 302's, the rpms stay pretty steady but it just shakes the whole truck like crazy. I will post a video of the shaking below. Oh yeah, I also thought maybe 1 cylinder was low on compression, I didn't do a compression test yet so I'm not 100% certain, but I put a bottle of engine restore in it, everyone that I have seen use this stuff it solved all of their low compression issues. With it in the engine now there is not the slightest difference in the way it runs.
 
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Old 11-08-2018, 06:34 PM
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https://youtu.be/6HhjgeSOaso
Here is a video of how much it shakes.
 
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Old 11-08-2018, 06:43 PM
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That exhaust leak may be your problem,air entering the exhaust plays havoc with the o2 sensor.
 
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Old 11-08-2018, 06:47 PM
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Hopefully that helps it, I'm pulling the manifold off now to see if I can weld up the crack in it for now
 
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Old 11-09-2018, 09:55 AM
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You may have to perform the compression check to prove you don't have an issue.

Check your plug color while there are out.

Check your plug wires for any wires crossing over others.
 
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Old 11-09-2018, 10:07 AM
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Originally Posted by CustomHD View Post
Oh yeah, I also thought maybe 1 cylinder was low on compression, I didn't do a compression test yet so I'm not 100% certain, but I put a bottle of engine restore in it, everyone that I have seen use this stuff it solved all of their low compression issues. With it in the engine now there is not the slightest difference in the way it runs.
The only thing this Snake Oil will do is clog your lifters a little more than they are already.
 


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