engine Bucking hesitating sound like its missing

[dean1997sport]

UPDATE!

I added some marvel mystery oil to my fuel and the problem is gone!
This leads me to believe that it could possibly be the fuel injectors but for now its totally gone.
I have been through dozens of threads with this same problem and not one really sound answer but this worked for me and cost under $6.00!
So if any one has a similar issue give it a shot it worked for me.

My 97 v6 ohv is having some weird issues.
Going up hill and on the freeway (flat, uphill, downhill) my engine starts to run really rough it hesitates bucks and doesnt want to rev. at cruise it runs fine when I floor it it runs fine with just a little hesitation. when the converter is unlocked its fine, when the converter locks at around 50 -70 MPH and I give it a little gas it starts to act like this.
It goes away after about 10 minutes on the freeway and it always happens right after i take off first thing in the morning or after its been sitting over 5 hours.
It isnt constant like i said it goes away after 5 miles of running on the freeway but its getting worse and im running out of ideas. I have searched on this site and have done just about all of the things that might be the problem.
No CEL light
did intake gaskets a few years ago my idle is fine

I have replaced the coil last week, wires and plugs about 2 months ago, cleaned the MAF and the throttle body.
TPS was replaced last year as was the fuel filter.

HELP!

 

[RomeovilleIL]

Bucking often is sign of weak fuel pump or bad fuel regulator (97-98 was changeover from return with regulator to returnless). Check your fuel pressure - initial prime, hold, and bleed down. Test regulator if you have one - might have hole in diaphram or vac leak.

 

[deweyville65]

Are you loosing any coolant? Mine (96 4.0 OHV) will do the same thing when it gets a bit of coolant in a cylinder from a seeping head gasket. After the plug cleans off, it runs just fine.

 

[curt1007]

I would say the fuel pump too,if it is the original it's probably due for replacing

 

[dean1997sport]

ok i will check the fuel pressure but again like i said its intermittent, today it didnt do it at all so if it is the fuel pump wouldn't it just die out with out warning?

 

[dean1997sport]

Are you loosing any coolant? Mine (96 4.0 OHV) will do the same thing when it gets a bit of coolant in a cylinder from a seeping head gasket. After the plug cleans off, it runs just fine.

I thought that too but it only does it when the converter locks the rest of the time it runs fine but as soon as the OD kicks on with the converter locked it starts hesitating like it wont rev or its missing.
When i floor it and it kicks down a gear it runs fine.

 

[dean1997sport]

bump!