New To Site. 99 F-250 5.4 rpms drop and falls on face at more than half throttle.Dealer road test with laptop said its running ok.Never over 8MPG around town.cleaned MAF,new air and fuel filters,DPFE,dealer changed #4 COP and all 8 boots.What else to look at?

 

check the pvc elbow where it attaches behind the intake,they are bad for rupturing.did they also change plugs when they changed the boots?

 

You mean pipe off air intake?Plugs were done at 75,000 now has 103,000. Still has 7 original COP's.Seems more like fuel or timing issue,maybe restriction.Feels like pulling a trailer when on a grade.

 

No, it runs from the passenger side valve cover to the rear of the intake manifold.

 

Any ideas on removal?Looks like one piece all the way with foam insulation on it.Cant get foam slide off and can barely reach end.Dont want to break tube if not already.This is a F-250,very tight against firewall,cant even get a mirror back there to see.

 

i wouldnt worry about getting the foam off.where it connects to the intake is a rubber elbow.you should be able to feel the elbow with your hands and twist it off the fitting then you can remove the other end from the valve cover and remove the entire assembly.or you can with the engine running reach back to the elbow and feel if its sucking air.hope this helps.

 

Well got tube off,its one hard plastic piece that goes in a rubber bushing on throttle body.Nothing wrong with it.Must be a different setup.Any other thoughts.

 

Fuel pump, pressure regulator, or clogged cat. Check those.

 

Where is the best place to look for testing procedures of FP & PR for 99 F-250 5.4?

 

I have always wanted to know, how do you check a cat to see if it is plugged?

 

I have seen it written on this forum once that you can take it to any muffler shop and they can drill a small hole in the pipe just before the cat to check for backpressure.

 

Just drove truck with no cat or muffler(LOUD)no difference,still falls on face.Must be fuel or timing i guess?Still have not found proper way to test fuel pressure.This a 99 F250 5.4 it is OBD 1,no O2 senors after CAT with no codes or lights on.

 

Do a vacuum test, it's cheap/easy and rules out some problems. With the engine running spray around the intake, tubes, hoses, ect with WD40 or starting fluid. If the engine revs up, you found a leak.

Is it a complete dieing or does it miss? Complete means a system wide failing, COPs will fail individually and cause misses. To check fuel pressure you will need a fuel pressure gauge ( wouldn't use any non-fuel approved gauge, fuels are bad on seals and pose a fire danger), take off the cap on the shrader valve (mine is forward on the pass side.) I don't know if ford requires you to disconnect the vacuum from the FPR.

If your O2 sensors or fuel filter are old, replace them. OBD1 was legislatively obsoleted in 1996 for OBD2, super duties are OBD2 compliant, but not strickly OBD2.

 

No vac. leaks.Just total lack of power,not a misfire.

 

Did you check the fuel pressure yet, as some have already suggested?

Otherwise... Gotta get into it and check the PCM for MAF flow - if it doesn't see any flow, or it doesn't change when you push the gas pedal, the MAF is bad...