Yesterday on my way up the mountain to get home from work, my truck (76 f-150 4x4 with 351w, 4-speed, 33" tires and 3:50 gears) began to miss at higher rpm's after climbing for an extended period of time. When I got home I put new plug wires on hoping that that would solve the problem but today after driving up the mountain it began to miss again once I got half way up the summit.

What do you guy's think is causing this?

I don't feel like re-typing my old problems with the truck so you can search them here.......

https://www.ford-trucks.com/forums/s...hreadid=163621

https://www.ford-trucks.com/forums/s...hreadid=162005

I have not had any problems with the truck since the last time the coil whent bad, other than the ticking in my rebuilt 351 windsor that I can't figure out.....

anyways it has been about 3,500 miles since the last mishap.....it has been driving nicely up and down the mountain durring that time except for yesterday and today with the occasional missing under load.


My thoughts are that

1) the new coil is going bad again.......... I have a mallory centrifigal advance dual point converted to electronic with a pertronix kit and an accell coil I am using a resistor also......does it sound probalble that it is the coil or the resistor?

2) It is related to the ticking somehow?!??! like maybe a cab lobe has wipped off......but my oil is still clean and it runs ok at idle.....

3) something is causing my engine to have preignition and in turn miss...........don't know how this could develop all of a suddin though??? maye cold weather??

 

How about plugging fuel filter? I've had it cause similar symptoms when operating under load.

 

Yup, a clogged fuel filter would definately cause that. That would be the first thing to change as it is the easiest and cheapest. Also consider putting a gauge to the fuel pump to check that it is putting out enough fuel pressure. They go out too and the engine wouldn't perform well enough under a load ie. climbing a hill. On Fords, another indication of a fuel pump failing, depending on what is failing in it, might be fuel shooting out of the mechanical fuel pump. (pieces of chevy dump fuel into the crankcase.) The lack of fuel might cause a lean mixture making a PING ?? Check timing too.
Tim

 

vacum leak , stuck egr,a couple more things to check

 

Maybe a stock fuel pump doesn't have enough CFM....I checked the fuel filter and it flows fine

I don't have an egr as I have a weiland stelth intake

I will check for a vacume leak tonight.

 

jpb,
A fuel pump has GPM (gallons per minute) at a given pressure. The fuel filter could cause this problem. Low floats in the carb could cause it also. What kind of carb are you running on that fancy intake manifold?
KingFisher
PS You said the vehicle was missing? Is it backfiring? If so, through exhaust or intake?

 

I have an edelbrock carb (the one that originally came with a manual choke)

when it is missing it is not backfiring it just hesitates for a second and keeps going then hesitates again. my speedo needle bounces a little and I can't accelerate as quickly.

once is did pop out of the exhaust but it was minor.

 

JPB,
This sounds like a fuel delivery problem. What elevation are you at? Have you done any tuning to your carb for elevation compensation? Did you just bolt it on out of the box? What kind of fuel filter are you using?
KingFisher

 

I am using one of the glass fuel filters and am at an elevation of approximatly 2,800.


I just bolted the thing on out of the box.

 

jpb,
You can look in the filter and see its condition. If it looks clean, then we need to consider tuning your carb for your application and possibly your altitude.
I am a flatlander and do not know if 2800 ft. is high enough to effect air fuel ratios. You should start a new post and see what info is available on that subject. I lived in Colorado for a short period of time at 8000 ft. and it made a huge difference. I would speculate a 20% HP loss or more. We seemed to correct our carbs by increasing the air correction jets. I'm not familiar enough with the elderbrocks to instruct you as how to do this correction.
Good luck,
KingFisher

 

does the edelbrock carb have a power valve in the front ? if so i'v had them to couse the same problem.and they are pretty cheap and easy to replace.

-All caps removed by admin- Please do not use all caps when posting.

 

The edelbrock does not have a power valve.

 

Does the carb have a fuel filter in it? Some have a filter behind the fitting you attach your gas line to. It can be plugged while your inline one is good. Best way to check an inline filter I've found is to try and blow through it, out of the truck of course. A partially plugged filter will be obvious. Just don't breathe any of the gas fumes.

 

All,
Another way to clear a filter is to hook it up backwards and turn over the motor. The fuel pump should backflush the filter.
Consider it,
Kingfisher

 

Well I replaced the filter and all seems well. I haven't driven it much yet though as I smashed up the drain plug of my oil pan while offroading so I took it off and gave it to a machine shop to modify.

My diff of my front axle hit the drain plug area and dented it in. so I am having them relocate the drain plug so it is in a better position (so it won't drain directly on the axle) and I am having them cut the smashed corner of the pan off and weild a flat plate on (chamfering that corner)....so i t won't hit it anymore......just hope that the the chamferd section doesn't interfere with the oil pickup.


here is a video of some of the offroading I did with a bunch of friends.. it is kindof big (46M) My truck did well except for starving for fuel on steep inclines


www.westpaxterraclub.com/video/CV.wmv