I have been driving my 98 4.6 for a few months and as I was going to work it started to shake at a certain rpm range. Like really bad so I made it to work and on my way home it continued, as I was coming up a hill it lost alot of power and motor got hot. I let the truck cool off them drove it home it done fine but still lacked alot of power. Any input would be greatly appreciated! Also it sounds like it's cammed which it's not, it's running really rough.

 

You'll have to scan check the engine for codes. Did the check engine light not come on? Does the light come on and go out if you just turn the key to run but not start the engine?

 

It's always on but it did start flashing when It started all this. I do have a few codes but it's for the o2 sensor

 

That’s not true. Flashing CEL is for a misfire, that is for certain. Post the codes and we’ll try to decipher them.

I guarantee you an an oxygen sensor isn’t at fault, but picking up engine conditions that are out of whack. Don’t shoot that messenger.

 

This is why it's important to fix the issues as soon as the light comes On. Once it's On you have no idea of future issues with the engine which can make repairs very expensive. For example a just happening leaking injector could ruin your catalytic convertor. An expensive repair.
As stated before, list all the codes your scanner will give in KOEO and KOER. Then the forum will have someplace to start with to help. Good Luck

 

Ill get the codes soon. And yes I know but I have a tuner on my truck being it's got long tube headers, trick flow heads, bigger injectors, intake etc so the programmer will give out codes but there's a reason behind it being the downstream o2 sensors ain't hooked up and needs new maf sensor. But that's never caused the truck to run this poorly. It definitely was missfiring but it's got new plugs, wires, coils. And it still dos this a man told me it could be a cracked head but I'll send the codes when I can. Thanks

 

All of these things are important to the diagnosis. Are there any other modifications to this driveline beyond stock?

 

Threads like this is why I don't post much, any longer.
Can't stand the ignorance and lack of common sense.

 

Yes, it would have been nice for the poster to say the truck was modified up front.

 

@Bluegrass 7 I def did list them just not right away but there is no need for your ignorance either you could just keep scrolling if your not helping. you say you don't post much I see why.

 

@Lime1GT yes I should have but don't be like the other guy I'm sorry I'm new to this forum stuff but I will get the codes tonight and send them thanks

 

Still need this answered.

Remember, we're troubleshooting your car from the far side of the internet, and we'll likely never see it in person. You have to tell us about all of the changes from stock, and any other changes or recent trauma that it has been through.

 

There are two codes they are surely going to have one for o2 downstream and one for their MAF sensor if the MAF is bad. Fuel is going to be bad as the airflow is off and it should be running rich from those two. When you run a code reader if you can get the one with live data. It should show you that I am going to say a plus 6 or maybe 9 from the MAF and o2. This would show a rich fuel from those two at idle.

Originally Posted by Wyatt4.6 View Post
it's got new plugs, wires, coils.

Wires? I hope you mean boots for the coils.

Originally Posted by Wyatt4.6 View Post
I have a tuner on my truck.

When was the tuner put in and what type?
You may need to check it.

Originally Posted by Wyatt4.6 View Post
it's got long tube headers, trick flow heads, bigger injectors, intake, etc.

Do you have the 185 or 195 heads from trick flow?
There is a big difference in these heads and how they are set up and ran. 195 are race type at around or just over 8,000 RPMs (off the top of my head).
You have the 4.6 engine and it was not set up from the factory that year for the PI heads. The 5.4 was and as such can take a grand of horsepower to the lower end of that engine. (the 1998 Eddie Bum expedition NPI -1999 f150 truck PI heads those years had the best crank installed from the factory and the bottom ends can take it)

bigger injectors: Who makes them and what size PSI are they? Some companies can and do have 10 PSI split in the injectors.
Your PCM / ECM controls fuel and with the tuner, I for one do not know what it is set at.

intake:Did you get a new one or have the one that came on that year engine port and polish?
I would hope it was ported and polished from the 5.4 intake metal one or one that was the full metal as the heads you placed on it is a PI type head.

In all like others, it is a lot of questions that need answers to help you.

 

He likely bought someone elses build, and has no real idea what he got.
That's why I said what I said.
I know it sounded insulting and picked it up right away.
He can't work on it and make any sense of the issues from lack of knowledge on a build like this.
We run a custom build 4.6 alum block with heads, larger injectors, headers, cams, custom fuel feed to correct injector flow and dyno tuned to run on the SCCA road race circuit in a 98 Mustang.
If there are aftermarket heads, the cam dial-in is not even same as stock. because the valves are relocated in the heads.

 

Damn: you running in the Grand Touring classes too or one of those types?
That Mustang is lite in the rear and I don't know if they allow y'all to add weight there or not.

A friend of mine ran in the old street British type a few years ago until his health made him stop.
Nephews work in Formula One race cars as engineers in their home country of England. (I am married to a Britsh woman and watched her go from a brunette to a grand gray-headed Granny)