Greetings,

Wondering if anyone can help with loss of power - rough running problem with 1994 F150 fuel injected 6 cyl ---

Great old truck had been starting and running just about perfectly. Recently, driving back on several hundred mile journey on highway started to lose power and run rough. Primary problem was loss of power but seemed to be accompanied by slightly more engine vibration.

Had hard time climbing and more accelerator was given worse it would run. Later, on flats, by easing off accelerator would run almost perfectly. Easing off accelerator usually always resulted in smooth running. During several hour drive alternated from running basically perfectly to having moderate power loss - but mostly running well. Seems like a fuel related problem - had totally fresh gas, switching between gas tanks made no difference. Open highway driving seemed to go best (if not perfect), when stopping for gas/street driving power loss/vibration was more likely (or noticeable) - but alternating between running perfect and power loss seems random. When it was running well it would then climb just fine. Engine gauges showed absolutely normal, all else normal, air temp nice 50/60s. After arriving home, truck still starts absolutely beautifully on first try, but has a slight "blip" in the idle every two or three seconds. Hope we're looking at a low-dollar fix ---

First thoughts: intermittent failing fuel pump, clogged main line fuel filter, clogged injector assembly fuel filter, intermittent injector failure, or injector subsystem related.

Highly appreciate any thoughts/ideas/suggestions on where to begin. Don't want to seem to be lazy but I've already got a lot waiting on me right now and any help with where to start troubleshooting would be highly appreciated ---Thanks very much!---

 

read code, read plugs, look at air filter, fuel filter, wires, cap/rotor, etc.

 

when was the last tune-up done.

 

In addition to stuff mentioned above, clean the throttle body out while your'e in there.

 

amissfire under load is usually plug wires, The blip at idle sounds like ignition system also.

 

Additional observations:

Truck has been maintained well and before this ran basically perfectly. Although the issue is something that has come up quickly, when loss of power was first noticed it started slowly over a minute or two, then wouldn't climb, then seemed to work out for a while. Failure seems to go from almost non-existent to loss of power randomly, on and off again over time, but easing off accelerator seems to always allow engine to pickup and go. Finally, after freezing cold night the engine starts absolutely *instantly* and runs *perfectly*, then after idling for a minute a small "blip" in idle is noticed. Seems intermittent and fuel related.

From my years with vehicles I get a strong feeling that someone familiar with/having seen this problem in a similar F150 could pick it out immediately. In a different truck several years ago I saw this identical problem and the fix was to clean the fuel filter screen at the input to the carb body. So, from that I might guess a clogged fuel filter/screen allowing the fuel pressure at the injector assembly to fall below a critical threshold. Sure, I might just go ahead and replace those, but rather than just a shot-in-the-dark all other suggestions highly appreciated.

Again, all thoughts highly appreciated.

 

I`m with QL2. Also if you are worried about fuel pressure you could put a gauge on it. I would check for a restricted exhaust. Good luck.

 

Thanks, guys - Well, checks seem to indicate that, wires look good, cap looks good, air filter looks good, plugs look good, and nothing unusual with exhaust - darn, the thing even had a fresh oil change and fan belt is new. Everything looks great...

Before I start ripping apart any one system and getting past the point of no-return I guess I'm still hoping for an educated guess on what to even be looking for - I guess the question is do I just start blindly replacing parts? -... Thanks for these and any other thoughts ---

 

Check your fuel pressure with a gauge to rule out fuel problems.

Pull the codes. Since you have a 1996, it's OBD-II. You will need a code reader, or perhaps autozone will read the codes for you. Do not buy electronic replacement parts from a parts store, they are all junk. Go to the Ford dealer or buy motorcraft parts online.

 

I will investigate pulling the codes but I'm not familiar with the procedure. Can you point me in to a website that gives details?

Also, correction: truck is 1994, not '96, sorry for the mistyped title - so, are codes still available on an original '94 engine? Thanks---

 

For instructions on pulling codes with a paperclip go to fordfuelinjection.com

 

Or Ford Computer Codes

The year makes a huge difference in this case. A 1996 requires an expensive reader, a 1994 can give codes using just a paperclip or short piece of wire.