Rough Idle

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Feb 10, 2017 | 03:02 PM

j-stephenson

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From: B

Rough Idle

I've replaced my Spark plugs, (time for them) then I had a missfire on #7, swapped coil plugs around and still there. And now I've pulled the fuel Trim and I'm not sure how to read or diagnose from that, if anyone could help that would be fantastic.

Feb 10, 2017 | 03:16 PM

pdqford

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From: Central NYS

Let's start off with what we are working on .

And what is the problem we think we have?

And why are we looking at fuel trims?

Feb 10, 2017 | 03:33 PM

j-stephenson

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From: B

Sorry, it's a 2005 F150 with the 5.4L and my apologizes its cylinder 4 that had the problems

I`ve had a rough idle since I bought it about a year ago. and in the last 3-4 months I`ve periodically had a Missfire, under a load or heavy acceleration. So I changed spark plugs (truck has 220,XXX KMS) I still had the missfire, then I swapped the coil packs. And found out that the Coilpack was screwed. Changed that out, and now I haven`t had the missfire since the coilpack was changed. But I`ve still got the rough idle.

A VCT was changed before i bought it.
Timing change as well.

I`ve linked the thread I had before

https://www.ford-trucks.com/forums/1...ough-idle.html

Feb 10, 2017 | 06:51 PM

pdqford

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Quote:

Originally Posted by j-stephenson

And found out that the Coilpack was screwed. Changed that out, and now I haven`t had the missfire since the coilpack was changed. But I`ve still got the rough idle.

Oh, okay. So w are not chasing a misfire under load.

But we are trying to solve a rough idle issue.
I think your fuel trims look fine so I wouldn't suspect a vacuum leak or fueling problem.

So I'd check the compression on all cylinders. A slight drop in compression at idle may cause an issue that might not cause an issue yet at higher rpm.

I'd also like to see what your scan tool's mode $6 data looks like for TID $53 on all cylinders to see if the PCM detects any misfire counts for any cylinder(s).

Does your scan tool see any other current or pending codes?

Feb 23, 2022 | 08:25 PM

nromes

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Check your MAF sensor. Last week I accidentally left MAF unplugged when I started truck and it idled roughly and when I tried to speed up and acted like it was missing. I shut off everyone and plugged back in and everything was normal. Your MAF sensor could be getting more dirty and cause problem to progressively get worse.