[Bunnychaser65]

Hi everyone, I am a new registered user of this forum, but it has helped me find answers on several occasions. Unfortunately, this time I am stumped. I have a 1997 F150 4.2L. Most of the time, it runs fine. Recently, I have been having problems while driving. It seems as if the engine will not take the fuel. It does not stall, it just loses all power, and the RPM's drop. Electrically, no loss, and if I push in the clutch it idles fine. If I press the gas pedal, the engine bogs down and will not accelerate. I had it in the garage for well over a month, and they can not find this intermittant problem. No fault codes come up. They have replaced the fuel pump, mass airflow,egr,and tested most all sensors related. Fuel pressure stays stable when fault occurs this was verified with gauge. ????? Any ideas?

I ran for the last 2000 miles without a problem, and yesterday it started again.

Thanks for you input!

 

[Mr Mac]

Welcome to the forum!

At first thought it sounds like an injection issue. Even with a fouled injector the fuel pressure will remain a constant. Do you have TBI or port injection?

 

[Bunnychaser65]

Port injection

Thanks for the reply, I don't know what TBI is, but this engine uses sequential injection at each intake port. Do you think a sticking intake manifold runner control would cause this? I did at one time, have that error code, but when I cleared it, it did not return. I have scoured my Haynes manual for clues, but I am at a loss. It almost acts like water in the fuel, but I do not know why it would be intermittant, or how it would have gotten there in the first place. When this problem occurs, I disengage the clutch, pull over, try to accelerate....and if it revs up I pull out again. Sometimes I drive several miles, sometimes it won't go 50 feet before it bogs down again. In yesterday's rainy weather it acted very poorly, but we have had other rainy days when it ran fine. Intermittant short somewhere? I don't want to buy another truck, but I can't rely on this one anymore.

 

[Mr Mac]

TBI = Throttle Body Injection

Does fuel pressure remain constant at all injectors or just as it comes to the rails?

 

[Bunnychaser65]

When tested yes, but the condition can't be replicated when it is in the garage. You seem very knowledgeable, are you a mechanic?

 

[Mr Mac]

I've had my moments! I am the son of a diesel mechanic who made sure that before I ever got behind the wheel of a car I knew what it took to make/keep it running! I have restored many an old Mustang and am quite comfortable working on the newer ones since my education was centered around electronics.

 

[SoCalBluFlame]

welcome to the forum