Here's one for you!!! (Runs Lean)

[steveissteven]

Okay, see what u can make of this. First off, the following have all been replaced. New TPS, Water Pump, Fan Clutch, Thermostat, Radiator, Radius Arm Bushings, Tranny, Spark Plugs, Spark Plug Wires, Fuel Pump, Fuel Filter, Fuel Pressure Regulator, Fuel Injectors (All 6), Serpentine Belt, Rear Leaf Springs, Tires, Vacuum Lines, Air Charge Temperature Sensor, MAF Sensor and probably a few other things I may have forgotten to mention. The problem I'm having is that while driving, vehicle seems to have on again off again power. While holding gas pedal steady, engine seems to surge as if one second it has optimal fuel delivery, the next second it does not. Sometimes like while on the highway, i will go to floor the vehicle in order to pass someone or to climb a steep hill, and there is nothing there (RPM needle does not even rise). Yet other times vehicle drives nearly new. I get no Check Engine Codes, and am going crazy trying to figure this out. Vehicle has been to Ford on several occasions (They find nothing) Seems to be worse the hotter it is outside. I live in Las Vegas, usually temperatures around 105. Any ideas? My fuel pump and Pressure Regulator are from NAPA. Fuel pressure at idle is 31psi. Are aftermarket pumps and regulators the same as FORD?

 

[tdavis]

I didn't see O2 sensors on your list.. they will cause this, if they are old or contamainted.

Also, check your wiring. Could be an intermittent short/open someplace. Does the lights dim when this happens?

You may also have a bad FPR - even brand new. 31lbs is right on the lower limit. Does it jump to 40lbs when the vacum line is pulled? If so, I wouldn't worry about it.

Last resort, check the intake manifold gaskets. They could be blown. You can also check the bolts, and make sure they are tight.

Does the truck consume any radiator fluid? How is it on oil consumption?

Another question - has it ever done this when stone cold? ie, the temp gauge is still below the 'N' mark. Or, does it get worse the warmer the engine gets?

 

[steveissteven]

Gets worse the warmer it gets!!! Intake manifold was recently (5 months ago) removed and new gasket installed to correct a coolant leak at the rear. There doesn't seem to be anything leaking anywhere. No oil and no it does not consume coolant. O2 sensors were replaced about a year ago with BOSH. Have never had Check Engine light come on. Problem is a lot worse when running AC. Temp needle seems to hang around the R in NORMAL, occasionally reaching the M if AC is on and temperature outside is hot. Does using after market parts such as the NAPA fuel pump and regulator and Bosh O2 sensors cause vehicle to run poorly? Will using FORD only parts make any deifference (Ford is so much more expensive!)?

Just runs like it doesn't always have enough fuel.

I am stumped!!!

 

[leebo]

Steve....I'd like to start of by sending a special Welcome to you. Check your email for more info.

I'm not too sure, but maybe the computer is going bad?? If the engine is getting mixed codes, wouldn't that cause gas to be sent on and off?? Maybe also a clogged cat??

 

[SteveVB]

Steve

As far as the Bosch O2 s they are OEM to Ford ( most I have seen are stamped Bosch) the FPR from NAPA I dont know.

Are you getting any codes? I would check/clean the Throttle body and IAC valve and solenoid, since you say it gets worse with the A/C load. I would also look at the injector O-rings and recheck the FPR and its vac lines, the t- into the manifold.

Good luck

 

[steveissteven]

Let me ask you this.... If the CAT is bad or going bad (becomming restrictive) wouldn't it be bad all the time? The vehicle runs the best the colder it is. The hotter it is, the worse it runs.

Is the CAT less restrictive when cold and more restrictive when hot?

Seems to me it would be just as plugged whether it was hot or cold?