Hiya all new here and starting off with my head scratcher.

Got a 98 xlt with 4.6 romeo in it.Had a spun bearing so instead of rebuild i got hands on a 4.6 from a crown vic with 70k miles on it.Oil,plugs looked great.\

Did the swap and getting po 174 and cant figure out what may be causing it.

Cleaned and took readings on the MaF and it reads good.
New PVC and tubing and elbows.
No changes with carb spray test pretty much around the whole top end.
No noticeable leaks at exhaust manifolds.
New motorcraft plugs with grease.
Main harness plugs ins cleans with electronic cleaner and greased.
Both O2 sensors reading good with scanner and voltages changes fine with carb spray introduced....passenger side o2 is also new while drive side is not.
EGR regulator solenoid tested out fine.
New fuel filter.
DPFE checked out good

Fuel pressure readings from valve on fuel rail reads
KOEO 38
KOER 30
With regulator unpluged goes to 40 psi

LTFT is about 3 on bank 1 and 30+ on bank 2

Unpluged fuel injector clips on each cylinder and no change in rpm on cylinder 5 and 6.Noid light check looked good as well as clicking with a stethoscope.
switched injectors from other cylinders to 5 and still no change in rpm when unpluged. Good spark when take bvoot off these 2 cylinders.

Checked compression and look good at 120 ish.

I am now stumped and starting to pull my hair out.....am i missing somthing or should i just rip apart the intake and throttle body clean them out and retorqe with new gaskets?

 

hmm that is weird you say the o2 sensor is new on the right bank im gonna throw a guess out there and say maybe the cat is bad on that side?

 

Dont think bad cats would trigger lean effects even then the right side isnt what is reading the lean fuel trim.

 

my bad the left bank cat a clogged cat can overheat the o2 sensors causing them to go bad but then again you said they were reading fine

just throwing my best guess out there youve checked everything else out already

 

Clear the code and see what comes back so you have the latest condition to run after.
What was the short term fuel trim reading?
Is the oil dip stick seated and tight?
Dip stick tube rusted through?
Vapor recovery system?
The problem has nothing to do with the Cats. They have their own monitor system.

 

Yes it will.

THIS. I had a cat go bad, caused a lean condition and shot me down to 9mpg. I took it to Ford and they diagnosed the bad cat. $100 for a pair of rear cats and $250 installation brought be back up to 20mpg

 

nope neither of these guys say that could cause the problem

 

Bad cats sets a code 420. Look it up.
The rear sensors look for oxygen storage with the PCM monitoring the switching ratio between the front and rear sensors each side.
What the dealer did not tell you was there was a code idicating the cats were faulty otherwise they was guessing and told you that afer the replacement. A very costly change.
Of course a plugged or burned up cat will reduce fuel mileage and power and possibly burn the front sensor and or rear sensor as a secondary result of the high temperatures.
Burned cats are the result of running the engine with a cyinder/s out and pumping raw gas back to the cats where it burned and the temperature go well above 1000 degrees to melt the internal structure.
A code 174 is not a cat issue directly. Never has been.
Look up the code and the causes.
I have the experience with all of this and not involving a dealer for second hand or padded positions where a lot of money is at stake..
Ford cat assembly one side can run as high as $1600.
It pays to know what your doing instead of guessing.
An air leak or some cause of rich or lean A/F ratio is being missed.
The code 174 can result from either a rich or lean condition depending on when the OX sensor reacted to it. Look that up as well.
The 'dynamic actions the PCM can do as a result, determies the code set.
It make little difference if the A/F is rich from extra fuel the OX sensors detects and shifts the tables lean or a leans condition the OX sensors see shifting the fuel table rich trying to adjust. Again it depended on when in the cycle it was caught as to the code set.
BTW I don't for one minute believe a Ford dealer ever replaced cats at $250 and 100 labor. Dealers don't normally work like that unless you got one that doesn't care or it was a used vehichle off their lot..

Good luck.

 

It has occured to me that you used a car motor for replacement.
That means you had to use the truck intake manifold.
Are you sure the manifold lined up with the ports in all locations and the gaskets used are correct, between the two motors?

 

Yea, that's what came to mind after reading the first post. Well, almost,- just in reference to the intake gaskets. Critical to be clean, -same w/matting surfaces before you set it on top. I've heard one finger print in the wrong place may cause a leak lol. Not sure about that one, -oil will for sure. A 3 stage gradual tie down is a must without over wrenching or THEY WILL leak, no doubt.

It's positive for lean and just on the one side. It doesn't have to be the intake gasket, but if I had to guess....

 

Yeah after this hurricane/storm passes ill be taking the intake off and putting on a new gasket cause really there is no where else to turn,after i do the intake if it isnt fixed will prob retest every component heh. Took the throttle body off and gonna take it apart and clean it in the mean time.

When i did the swap the intake gasket was one of the few i didnt replace cause it looked really clean and was part of the truck assembly.......oil pan is another you can reuse but i went with a new one there cause didnt want to risk that.

I suspect the #5 and 6 cylinder area is the area of issue since when take the plugs and injector clips from here there is no rpm change.Must be a hell of a leak tho......

You mention a 3 step bolt down sequence but all data shows 2 step.......hand tighten then 15 to 22 lbs....is the info i got wrong?Next question if it is a 3 step then are these TtY bolts?

 

code 174 is back after car sat all night with no battery
Short term is doing what the long term does on that bank ....starts climbing to 30+ the more i give gas with the long term going to around 0.
Dip stick is fine..no rust and clean.

Since fuel pressure is good and readings are good on rest of vehicle and only getting code on driver side bank/o2 sensor did not look over the canister or iat sensor and such.

 

well pull my hair and call me sally you never said in your original post anything about re-using the intake gaskets i dont know about anyone else but me personally I would never re-use gaskets as important as that

 

Ok here is a update:
installed new intake manifold gasket and not seeing much of a change still rough.

Here is live data from scanner if any can point to somthing amiss from thewse4 numbers.

this data is from truck running idle for about 30 mins and observing each data point for roughly 30 seconds.

Calc Load% 20.9-23.1
ect 190 degrees
stft b1 -3.9-2.3
Ltft b1 4.6
stft b2 -1.5-7.8
Ltft b2 20.3-22.6
eng rpm 677-729
spark advance 11-20
IAT 75 degrees
MAF (lb/min) .685-.816
TPS(%) 18.4

o2s b1 s1(v) .090-.790
stft b1 s1(%) -3.1-2.3
o2s b1 s2(v) .730-.790
stft b1 s2 (%) na

o2s b2 s1(v) 0-.750
stft b2 s1(%) -3.9-4.6
o2s b2 s2(v) .025-.785
stft b2 s2(%) NA


Update: went outside and checked the ltft and its increased now the range is 28.1-29.6

 

How did you install the gaskets ? Which manufacturer did you use ? Are you still getting just the one bank lean DTC. You hadn't posted much useful info, so....