Recently I have been having an issue with the truck bogging down under mid to full throttle. Im not sure where to star . I have tested the fuel pressure at 54psi with no changes. I have replaced plugs, wires, Iacv, TPS. Im not sure where to go from here.
The sensors are autozone parts due to shortness of time and trying to diagnose. Found no change with the new ones compared to older ones.
Any ideas?
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No check engine lights?

I’m guessing you checked the air filter

how many miles does it have and do you have the OG o2 sensors

Typically when you first start your truck the fuel system runs on an open loop

once your o2 sensors get hot enough it switches to a closed loop where it adds a certain amount of fuel depending on how much oxygen the o2 sensors say are in the exhaust

if they are going out they can say there’s too much or too little oxygen and it’ll make you run rich or lean


does it ever idle poorly?

only other thing I can think of is the maf but o2 sensor seems to make more sense

 

Clean your MAF sensor too, use the special cleaner and nothing else.

 

What is your fuel pressure at when your engine is under a load ? not sitting in the driveway reving the engine, but driving down the road going up a hill.

Could just be a plugged fuel filter and starving for fuel.

 

For sure double check fuel pressure

to check the o2 sensors go into the live data and see what your up stream o2 sensors are doing they should be constantly alternating back and forth

 

The idle has been terrible due to something I'm not sure of. At a stop light with a/c on, it feels like I'm trying to spool turbos up. It lurches forward while on the brake.

I have no code . I had a iacv malfunction months ago, misfires and a lean code, but all that seemed to tie into the plugs . One of them was missing the inner igniter.

Its an 03 with 137k miles. Wasnt driven long distances. Previous owner had to bust out the cat which I had to fully clean out, didn't make any difference in either situation.

Fuel pressure while driving and accelerating hard is still at 54 psi at the rail. Don't have any hills here locally to drive up lol.
The idle has been an issue im trying to figure out with the bogging. It's only when I drive it for like 5 minutes it'll then go to crap. First five minutes it is perfect.
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I would seriously suspect your o2 sensors

like I said once your car first starts up it doesn’t run off o2 sensor feedback so it runs fine but once it warms up the fuel system relies goes to closed loop and relies on the o2s to calculate how long to open the fuel injectors


it’s normal for them to go out they send a voltage reading to the computer based off how much oxygen is in the exhaust. It has a certain chemical in the sensor that reacts with the oxygen which is how it gets a voltage reading. When that chemical runs out it doesn’t send the correct voltage to your computer.

then ur computer adds the incorrect amount of fuel to the engine and it runs like ****

 

Isn't there like 4 o2 sensors or is it just 2? I found one on the cat I blew out, and the other seems further up on the driver side.

I currently don't have an ob tool to check the live data. Any other option?

 

Your gonna wanna replace your up stream one

that’s what computer uses to adjust fuel trim

you have a v6 or inline 4?

v6 have one for each bank inline 4 only has one bank so one o2

o2 sensors run $30 a pop for motor craft OEM ones on oriley so it’s up to you if you want to gamble but instead of guessing I typically like to confirm the problem somehow

do you have a multimeter ?

 

I can use one.

And how do I know which is the upstream one?

 

I have a 3.0 flex fuel

 

If I’m being honest I know that flex fuels can run on higher ethanol fuel but idk how much different they are mechanically than a gas engine

BUT

on gasoline engines the upstream o2 sensors are the ones closest to the engine. Typically right after exhaust headers and before catalytic converter.

if you have a v6 you have an o2 after each header on each bank

 

Thanks. Will look into it coming shortly in the near future.

 

The flex fuel will have larger injectors and a different shaped combustion chamber.

 

So, even without a check engine light now, you still think it's o2 sensors? Read alot, most people say they don't go out without a code. I did have one lean code, but haven't had it since. Just a thought.

 

With the "Busted Out" cat, you should have a check engine light.

You say you have no codes, does the CEL light work?

Key in the run position and engine off, it should light up.

 

I have no codes actively showing up. I'll have to check when I get home. Currently at work with my car. Like I said before, I had a b1 lean code. Cleared all codes when I replaced the plugs due to a multiple misfire, found one plugs middle igniter missing. Others seemed fine though. It doesn't run well enough or has enough acceleration to run on the interstate, so I'm due to having to leave it at home.

Not willing to get rear ended because the pos can't accelerate faster than a turtle. 😂

 

If I'm being specific, it's the part of the exhaust right after where the main exhaust cats merge into. The one before the muffler. If that helps any for which one is "busted out".

 

2004 Mazda B3000 (3.0L)

I replaced all (4) O2 sensors at 155,000 miles, I ordered them from Amazon with no problems from this manufacture:

The IAC needs to be from Motorcraft. I tried an aftermarket and it did not work. I ended up cleaning the original IAC and now smooth idle at 750 rpm with no tach needle movement.

 

You could buy the 4 pack for 50 but they are not oem

you could buy two motor craft ones for $60 amd just replace your upstream ones because that’s what your computer uses for fuel trims so I don’t think your downstream o2 sensors would cause your poor running problems

it’s up to you but whatever you do replace the upstream ones...

 

Thanks for the replies. Going to start off with the motor craft iacv and see how that does then go to the upstream o2s

 

Anyone know a link to the relearn process for the iacv?

 

Disconnect the battery on the negative side and let it sit for at least 30 seconds, some say a minute.
3 driving cycles will be enough for the PCM to relearn anything.

 

As in cycling and starting or just cycling on and off?

 

Driving it for at least 1/2 hour and then shutting it off.