Rough idle, up and down
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Joined: Apr 2018
Posts: 88
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Rough idle, up and down
Okay so final story is, i got everything on my truck running fantastic, has the power it used to, and everything, gas mileage is still below normal at about 9mpg but still, anyways.... so when i pull in parking lots and have to drive slow or something to park or look for a spot, it will start to fluctuate back and forth and idle super low, at like 350, then jump to 600, then to 350, then to 600, over and over for about 15 seconds untill i give it gas, any ideas, 4.6, changed plugs 4 months ago, and fuel filter, dunno if they are bad already or not, dont have any codes, o2 sensors were replaced last week, TPS and IAC were replaced brand new last week
Senior Member
Joined: Mar 2016
Posts: 6,548
Likes: 486
From: South-central Ohio
What Whitey and Brew are trying to tell you, in many different ways, is that the engineers and designers at FoMoCo are a lot smarter than we are- they designed these engines/trucks to do a specific job under specific conditions and ( contrary to popular belief) to do that job economically as possible for a reasonable amount of time.
The systems incorporated on these engines are put in place to do just that- any deviation/ modification is detrimental to the operation of these engines/trucks.
Yes, you can electronically modify/ delete/ jump around factory settings with a “tuner”- but again, the engineers know more about these engines than outside entities.-
You can fiddle-fart around and eventually throw in the towel and bad mouth Ford after you give up, or you can read, listen, study, comprehend the information available to you. Most folks here will tell you that its no easy task- but it can be accomplished.
Now, apply yourself. Youll be amazed.
The systems incorporated on these engines are put in place to do just that- any deviation/ modification is detrimental to the operation of these engines/trucks.
Yes, you can electronically modify/ delete/ jump around factory settings with a “tuner”- but again, the engineers know more about these engines than outside entities.-
You can fiddle-fart around and eventually throw in the towel and bad mouth Ford after you give up, or you can read, listen, study, comprehend the information available to you. Most folks here will tell you that its no easy task- but it can be accomplished.
Now, apply yourself. Youll be amazed.
98 F150 5.4L E40D/4R100
Joined: Nov 2006
Posts: 28,520
Likes: 7,632
From: MI
This info doesn't apply to all generations of catted vehicles, that's how folks get twisted in their beliefs about running cat-less. For this gen, running them in open loop (default) which you are, will run them into the ground quickly.
The problem is this engine like others uses inputs from the oxygen sensors to modify the air fuel mix. There is an oxygen sensor before the CAT and one after the CAT to measure how good of a job it is doing. On these trucks this means your engine will not run as good (certainly not as efficiently) because without those inputs from the oxygen sensor it won’t dynamically modify the air fuel mix and the spark timing, it will just run off of presets as if the truck is still warming up (open loop vs closed loop). Your running the engine out of margins...the factory programmed parameter margins in which it cannot compensate for. This gen vs others takes a big hit in performance and overall, how it's designed to run. So much so, it will eventually burn them up. I wouldn't be surprised if you cooked those new plugs already.
The problem is this engine like others uses inputs from the oxygen sensors to modify the air fuel mix. There is an oxygen sensor before the CAT and one after the CAT to measure how good of a job it is doing. On these trucks this means your engine will not run as good (certainly not as efficiently) because without those inputs from the oxygen sensor it won’t dynamically modify the air fuel mix and the spark timing, it will just run off of presets as if the truck is still warming up (open loop vs closed loop). Your running the engine out of margins...the factory programmed parameter margins in which it cannot compensate for. This gen vs others takes a big hit in performance and overall, how it's designed to run. So much so, it will eventually burn them up. I wouldn't be surprised if you cooked those new plugs already.
Last edited by Jbrew; Jul 11, 2018 at 02:43 PM.
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Joined: Dec 2015
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From: Utah
Pretty much sums it up ^^^.
You can go catless on a small block Ford with EEC-IV with zero issues. It won't even throw a code. But these trucks use them to run the aforementioned programming, and it does not compensate to change like the EEC-IV (with MAF) does.
You can go catless on a small block Ford with EEC-IV with zero issues. It won't even throw a code. But these trucks use them to run the aforementioned programming, and it does not compensate to change like the EEC-IV (with MAF) does.
Thread Starter
Member
Joined: Apr 2018
Posts: 88
Likes: 3
Ive had many trucks with cats deleted before, my buddies 98 f150 is deleted, and many more people ive seen, and no one has these problems, i have alot.more power and throttle response since deleting them, and the issue im having only developed last week, and its not all the time, so im not gonna believe its the cats