Rough idle no CEL
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Mountain Pass
Joined: Jan 2017
Posts: 101
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Rough idle no CEL
Hi again! My 2006 f250 5.4 (167k miles) has a rough idle, we have done an injector cleaning, new vct solenoids, maf cleaning, plugs, coils, fuel filter, driver side cam, rockers, lash adjusters, checked fuel pressure and replaced the intake runner valve actuator as it failed. Last time we checked the drivers side bank was showing misfires but didnt throw a light. Cam phasers and timing job were done 12k miles ago. Truck has a loss of power and idles rough when hot, cold idle is less noticeable as the "roughness" goes away starting about 1k rpm. I checked evap purge valve using a multi meter and got 4 ohms which other threads seem to say is normal. Any ideas?
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Mountain Pass
Joined: Jan 2017
Posts: 101
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If i remember correctly the fuel trims were fine but I can check them again as its been ~5k miles since we checked them. Yes OE Ford phasers were used.
Fleet Mechanic
Joined: Oct 2017
Posts: 1,704
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From: Southwest Ohio
Hook up an old school vacuum gauge and see if you have a steady needle. If it’s jumping around, you have a mechanical issue (then pull valve covers and inspect rockers and springs). If needle is smooth (and good vacuum) you should see some non-normal fuel trims.
— Dave
— Dave
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Mountain Pass
Joined: Jan 2017
Posts: 101
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sorry the for the delay. I purchased a vacuum gauge and tested the engine. Although the engine was misfiring/ rough idle while testing it held 20 in hg. at idle. Needle was smooth, when reved to 3500 rpm it helded about 3 in hg. above normal for a few seconds and came back to normal, quick rev it went to 0 up to 25 then back to 20 in hg. No oscillation, drops, drifting or anything that seemed off. Needle was steady through the whole thing. I used the evap inlet on intake manifold for this test.
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