Engine is laying down under moderate hard acceleration

I noticed that if I jump on the throttle to accelerate kinda hard the engine will act like I hit a rev limiter...Except that now it has started surging between 2-3k instead of 4-5k.. I measured the fuel pressure at idle and it is 65 psi +_ 5 psi but I don't have a gauge on the system to measure it while I am driving... BTW the truck will run up to speed if I accelerate easily and will cruise just fine...And I am not getting any codes on the engine either...

Obviously dropping fuel pressure would cause this problem but I am wondering if there is something else I am missing... I think I will be replacing the fuel pump in due time after I put an electric fuel pressure gauge on the truck since I bought a new one but got the original to work...

But since I don't have the history on this truck I have tuned it and rebuilt it as needed but I am worried that fuel pressure may not be the only issue...

Any ideas what I should look for?

Some places to start looking Fuel filters, cats, injectors,

how many miles? is this an automatic?
no check engine light?


I would think low fuel pressure also

This truck has 151xxx when I bought it and has 152500 on it now.. It is an automatic that I replaced the sending unit/fuel pump with a boneyard unit...I bought a new unit for the trucks' original sending unit but have not installed it yet...I have replaced the fuel filters[in tank and under car] twice so far because the tank had 2 years of fuel left in it...That was cleaned out of the tank before I started driving the truck..

I have changed the injectors thanks to one of them being a bit sticky and that brings up a new issue...The remanned injectors are 13 lb/hr instead 19 lb/hr and that is a feature with the truck being from Calif... I would like to use 19 lb/hr since I have new ones of those and I am thinking the MAF for 19 lb/hr injectors could be used in place of the 13 lb/hr ones and frankly I don't like the 13 lb/hr injectors for this engine...

I have no check engine light, no stored or pending codes, and if I don 't drive this truck hard it runs well.. I drove it over 450 miles on the highway and 600-700 miles around town and it only seems to be a fuel starvation problem when I get on it hard...

I am thinking it is time to swap this v6 for the v8 in my Ranger....Sooner than I planned...

Try some seafoam in your vacuum line and gas tank. It will help if the problem is clogged cats.
http://www.youtube.com/watch?v=SRfVcvcMycc

Already ran Seafoam through it looking for the dead misfire...

The engine and catalytic convertors are in remarkably good condition...Found the misfire when I pulled the pass side valve cover and saw the intake pushrod laying against another valve rocker arm...

The seafoam smoked the exhaust and did remove some of the carbon in the engine but it did not fix that mechanical problem...

I am at a point of adding an electrical fuel pressure gauge from my Ranger to my Explorer and then watching if the fuel pressure drops under hard acceleration.. I am hoping that it does so I can justify changing the fuel pump/sending unit in the tank and then maybe go to 19 lb/hr injectors and appropriate MAF sensor...

Update to this problem...

After getting a load of water and rust to go along with my gasoline, I finally installed my fuel pressure gauge after installing a new fuel pump..

At idle and slow acceleration pressure stays constant...Push the pedal past halfway and the needle drops like a rock off a building...

The pressure gauge starts the cycling up to 70 and down to zero if I hold the throttle open far and long enough...And this is after draining the tank and adding fresh fuel[verified fresh and water free]...

So I am about to drop the tank to see if there is still varnish in the bottom that is displacing the liquid fuel under acceleration...Or something being sucked into the pump strainer instead of fuel under acceleration...

I'd consider dropping a torch into the gas tank ...But I bet this thing wouldn't burn....

Any ideas welcomed...

Might want to replace the fuel lines first. Its cheaper and if there is a piece of rust stuck in them then it would allow the fuel rail to have full pressure but then the flow would greatly be reduced. You could just run rubber hose the whole way. Easier to run and cheaper.

The bigger injectors would probably help if you found and installed some.

I'd look into getting the ford procedures for trouble shooting this. I bet thier service manual has stuff you can check in it.. Sorry I can't be more help..

Final update to this problem...



The work is done and the truck is running well...

Found the reason the fuel pressure was dropping...There was so much garbage in this fuel tank that I am surprised the engine ran... Even though I drained the tank and did a cursory clean out when I started working on the truck...

Removed the tank and sending unit Sunday and when I pulled the pump/sending unit the strainer was caked with solids...Mostly varnish and dirt apparently...This was only a week old install...The new pump actually caused this problem to happen faster since it was pulling more fuel into the strainer and more of the debris in the tank into the strainer... At least the fuel filter caught the lions' share of this crap...

Time to break out the big guns...Do I buy another tank or clean this one? Being currently in a foreign country[ Galveston, Tx after hurricane Ike] buying new parts is a joke and there are no radiator/gas tank shops here at all so I decided to clean it out...Used high pressure washer with caustic cleaner initially, then added 3 gallons of Purple Power full strength sprayed constantly into the whole tank then shaken for an hour...Drained it out and saw the additional debris that came out and the inside of the tank change colors from a dirty brown to silvery metal color...Then dried it with compressed air and poured in MEK to do a final clean of the tank. Agitated it for an hour as well and then poured the brown mess out and reapplied more MEK... The second solution came out a LOT cleaner and the residual MEK evaporated quickly[don't breathe it unless you like the smell of acetone]...

Reinstalled the pump after installing a new strainer and reinstalled the tank into the truck...Added 2 gallons fresh fuel and started engine...Pressure hit 70 psi and drove to a fuel station... Added 5 gallons and took it for a high speed run on the highway...

Verdict...Fuel pressure gauge never varies more than about 5 psi up or down... Engine pulls hard from a standing start and the engine temperature is actually lower by 10-15 degrees so far...

Frankly I could kick myself for not doing this when I bought this truck in Austin where facilities are available to clean a gas tank but my assumption that the varnish in a tank would eventually flush out with the fuel being used was incorrect...This tank was by far the worst I have ever seen that had never been underwater....

Thanks for the update. Glad you found the problem and that it was a cheap fix. Runnin like a top

After you run a few tanks of fuel through it you might want to change the fuel filter one more time. Just a suggestion