Okay today I got me a new maf from prozone and changed my plugs to motorcraft sp500s. I checked all my spark wires good resistance good coil pack resistance 12.5-13.5 ohms and reset the battery. When I put the truck WOT, It gets up moves fast until around 40 the seems like it takes forever to get to 60. My 0-60 times I've noted is 12.8 n 14.2 before the work and I still got a 14.0 with all this new stuff my 0-40 time is like 5.5-6secs. Wot seems terrible after 40.

I have no intake manifold gasket could that be a issue? I typically have check engine light that always says something bout the cat bc I gutted it

I have new maf, plugs, and fairly new O2 sensors, put in no ethanol gas n have drop in k and n.

Any ideas on what could be issue about this. I want to run atleast 10 sec on 0-60. I want to do tps sensor mod and I have done the zip tie cable mod.

I just want more power espically when wide open.

 

I assume you mean upper intake gasket is missing?
I would think you would have a stumbling idle if it was leaking air.

It could be a clogged exhaust issue, you "gutted" the cat??, what about muffler condition.
FYI, Federal Law, so in all states, sets a $2,500 fine for "modified" cat converters, and they in no way limit performance if working properly.

I have never ran across an issue with rear O2 sensor causing a performance issue, BUT(big but, lol) that being said I wouldn't put it past the software writers for the computer to add a limiter if CEL(check engine light) was on from a high emissions report from rear O2 sensor.
O2 sensors don't work under 600degF so are not used for at least 5 minutes after cold start, I would reset computer, then I would test if you get better performance in the first few minutes after cold start, if so it could be a software program restricting performance because of the no Cat issue.
But never heard or read about that.

Vacuum gauge is inexpensive and can tell you if exhaust flow is limited.
Also general engine condition
Have a read here on the different tests:
Technical Articles: Engine testing with a Vacuum Gauge - at Greg's Engine & Machine

Do you have a manual or automatic?
Shift solenoids on the automatic could be selecting wrong gear for best torque above a certain MPH.

Older fuel Filter could be limiting full flow, or fuel pump could be wearing out, you could test fuel pressure at 2,500rpms for a minute or two and see if it starts dropping.


And a little FYI about exhaust systems, bigger is not better, velocity is what "lowers" back pressure at the exhaust valves, larger pipes can lower velocity so increase back pressure at the exhaust valves.
That's where the myth of "engines need some back pressure" comes from.
People put on larger header pipes and lost power..... "WTF", engine must need back pressure, lol, correct result wrong conclusion.
The proper pipe size for the engine cylinder volume creates a velocity in the pipe that will create a lower pressure at the other exhaust ports on that bank, this design is above my pay grade but suffice it to say, a properly "tuned" exhaust will create a lower pressure at the exhaust valves.
Which means better performance and better MPG, which is why manufacturers do "tune" exhaust systems for best mid-range performance, after market headers can "retune" them for better low-end or top-end performance, not both, lol, and it just changes the power range Lower in RPMs or Higher in RPMs it doesn't increase it.

 

So your trying to drag a 4.0 OHV Ranger?

Well, Insanity aside. I can't believe you put the upper intake back on without a gasket. Spray some carb cleaner around the manifold while the engine is running, If it gets sucked into the engine, it'll sputter.

Is your truck tuned? Because if your serious about this, your spending money on the wrong items.

 

Kansas has no emission laws so it's all good. It not tuned I just want the stock power back. My year and engine is suppose run a 10.5. I'm running 14 0-60. I have a automatic trans. After I reset the computer it gets worse performance, bad bogging. Still have stock exhaust. I was thinking bout changing the filter and doing some pressure tests because I wanna get to the bottom of this.

 

Cat converters are a Federal beef, so State emission are moot.

And just as a "heads up" shops that do automotive work can get a $25,000 fine for modifying Cat converters, AND for not reporting modified Cat converter vehicles.

A shop can make $400-$1,000 installing a new Cat on a "reported" vehicle, so not only is it "the Law," but they can make money on it, lol.

 

Well I am bout to get my exhaust replaced but I'd still love to know why it's running like this.

 

A live scanner would really help, might be able to rent one.

I know the Bluetooth scanners run about $45 and you watch the data on a smartphone or laptop with bluetooth

Could be your EGR valve, if so equipped, is opening too soon which will limit power

 

My 4.0 doesn't have a egr valve. Little note: from thread start ever since new maf and plugs my check engine has not came back on. The. If keep constant speed at 60 n up it seems like there a little misfire or delay I think I got a faulty wire now, I changed around my new and old wires bc new ones are cheap oreilly stuff

 

May have to look

 

I think stock spark plug gap is 0.054
You can change it to 0.049 to have better higher RPM performance, less misfires.

Even 0.044, although it might be slow to start on cold days

 

Ok I think found problem, tested my pts and it read a 4.7 so ya not good.

 

That's great!

What's a "pts" and why is 4.7 bad????

TPS(throttle position sensor) should read .6-.9volts when throttle is closed, 4.5 to 4.9 volts when throttle is wide open.

The TPS is one of the "learned" sensors, it has no "exact" setting/voltage, computer goes to wide open(WOT) when ever it see 4.5v or higher, but it will learn that the highest voltage is 4.7v at WOT, and the lowest is .8v, for example, and will use that to set the range.

 

I read tht n seen tht it's not suppose to go pass 4.0 volts if it does it's back

 

Well whatever you read about the Ford TPS needs to be corrected, please post that link and I will send them an email, or you can.
Throttle closed .6-.9vDC
Throttle open full 4.5-4.9vDC

 

I watched a video on YouTube that he put a multimeter to his pts and it would stop at 4.000