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re: F-150 Question

Posted on 5/1/17 at 12:08 pm to
Posted by cajuncarguy
On the road...Again!
Member since Jun 2013
3135 posts
Posted on 5/1/17 at 12:08 pm to
Carbon build up in combustion chamber is frequently the culprit. Of course you should change the plugs @100k and ensure a clean OEM air filter. Assuming no codes.

But some discount gasolines don't have the additives to keep the valves and comubstion chamber clear of carbon. This buildup decreased the effective size of the combustion chamber thus increasing the compression ratio. Also when this carbon gets hot it can glow like a glow plug. SO the effect spark knock. When the knock sensor detects these knocks it retards the timing reducing performance and fuel mileage.

So the cure is to have a combustion chamber cleaning service done by a COMPETENT shop. You may be able to get some improvement by running Tier 1 fuel with a lot of cleaning additives. Chevron, Exxon/Mobile, Shell, etc. Run it like you stole it. It may take several tank fulls.

I have a 2011 5.0 F150 that I use only Shell and Chevron and at 73,000 miles it runs as it did when new.
Posted by TSam
Member since May 2010
122 posts
Posted on 5/1/17 at 12:10 pm to
Catalytic converter
Posted by CP3
Baton Rouge
Member since Sep 2009
7425 posts
Posted on 5/1/17 at 12:45 pm to
My main issue is sluggish (not terrible) and a rough rough idle. Knocked out Evap valve. Ran Lucas oil fuel system cleaner and a few tanks of 93 octane.

I have a scanner and it shows 5-10 misfires on 2 cylinders in the last 10 drive cycles. However it also shows status "OK" next to this and I don't have any codes. I'm assuming a very small amount of misfires isn't an issue as it shows status "ok"?

Like I said spark plugs will be next. I know oil and air filter are good. Reason I thought it was Evap related is bc my fuel gauge only reads 3/4 full after fill up. I know vacuum problems can mess with fuel reading sometimes
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