whaaatever floats your boat bud. the OP still has a missfire problem.

 

Alright, so here's another idea to throw out there: I was talking with a friend today who had done a fair amount of work on GM products, and he said my symptoms sounded pretty similar to a bad fuel pump, and suggested I check the pressure. Well, I did, and I'm only getting 25 PSI! According to the Chilton manual, it should be 55. So I guess what I want to know is, are my symptoms at all consistent with a Ford fuel pump going bad, or is this irrelated?

Thanks,
Josh

 

The proper fuel pressure for a Ford modular is 40psi at WOT. So,to check it properly,you must put the tester on the fuel rail and remove the vacuum source from the regulator to simulate WOT.

JL

 

Had the same issue! 97 F150, 260k miles. Truck bought new and has been maintained by myself since new.

Started feeling the tranmission hunting at 40-45 miles per hour under light load. Began to think, given the miles, transmission was due for overhaul. No codes from engine or transmission. Hit the OD off switch and hunting went away. After a few weeks even turning off OD did not help. Again no engine or transmission codes. Really starting to get worried!

Another week or 2 went by and soon it was really getting bad. Also noticed engine stumble at idle about every 15 to 20 seconds. Now thinking engine issue. Still no codes.

Finally got fed up and started trying to get the stumble and gear hunting. Had the code scanner hooked up and it finally threw a P0305 as a pending. Now we are getting somewhere! Darn if the pending did not go away within a minute or two. Drove it hard again, got the pending P0305 which went away again. Crazy I know. Without the scanner hooked up would never have found it.

After the engine cooled off, replaced the coil pack with a spare I had. Now the p0305 was picked up and Check Engine light came on with the flashing CEL misfire. Finally narrowed it down to the number 5 wire. $5 fix and now running as smooth as when it was new. No engine stumble, no transmission gear hunting.

Sorry for the long post, but reading all of the other replies sounds like it may be similar problem. The ONE thing that saved the day was the code reader hooked up real time to pick up the pending code. Would never have found it until at some point the wire/pack totally failed.

 

You have proven a point I've made may times.
Most who come to the board are not experienced with these systems to the point they think things are simple until it becomes clear the issues often require advanced handling.
These trucks are COMPUTER controlled and need to be viewed from that point.
A mid range or better scanner, not a simple reader, is required as well as the user needs to know how to interpet what data it provides.
My last cylinder issue was caught with a scanner set up to "trigger" and lock on a fault while driving.
Changed the coil of the cylinder trapped, and nailed it the first time.
On my truck, I have no plug wires to go bad, only coils.
The intermittant nature makes it difficult to know which cylinder is the offender because no code is set.
Heat causes shorted turns in coils and changes with temperature as well as engine cylinder load.
Since it is almost never a hard fault, there is no 'immediate' code and CEL set to make it that easy to tell which cylinder has the issue.
.
How does the PCM look at the cylinders for issues?
.
....The front crank sensor "measures" the rotation time for each cylinder and compairs it to 'soft tables' in PCM program memory. When any cylinder slows to the point it falls outside the table values for that cylinder compaied to the whole engine average, a logic decision is made to alert by setting a code.
Under an intermittant condition, you can see it has to handle it with some tolerence if the issue is not a solid hard failure.
Further, this method also allows the 'soft tables' to change their averages as the engine ages and cylinder average pressures cause rotation time to slowly lengthen to account wear and aging.
Pretty clever!
Good you got your problem solved..

 

Wow. I don't really participate on these F-150 forums too much just because there is just way too much blatant stupidity such as this. I think I may start attempting to correct such misinformation so people are not mislead and hopefully uninformed people will stop acting like they know everything.

1) Our ignition coils definitely can and do degrade and don't always just stop working. Cheap knockoff coils are especially prone to this.

2) Yes the coils do put out more energy than needed. There is no downside to having a hotter stronger spark. A higher voltage the outputted to the spark plug by the coil results in a hotter, longer lasting spark, that generally does a better job of igniting things. A coil works by having current supplied and stored on one side of an induction coil. A magnetic field is created that stores energy. The current is removed to fire the coil and the magnetic field is disrupted. At that point ALL the stored energy is passed to the other side of the induction coil and the spark plug fires (hopefully).

3) Unfortunately, spraying these coil packs with water is not the best idea. If there are cracks in the upper housing, water can get into the coil and cause more problems.

4) A misfire here simply refers to a cylinder not firing. It can be caused by a number of things.

5) Opening the spark plug gap will not necessarily produce a better spark. If your coil is producing a large amount of voltage, you can open a spark plug gap to produce a larger spark that will sometimes produce more complete combustion, but if the coil does not produce enough voltage, it will just be a lot more likely to produce no spark at all.

6) The "cool electronics" is just an ecu. Pretty much every modern car has one. It tells the injectors how much fuel to supply and tells the coils when to fire based on feedback from sensors. Yes, of course rich fuel mixtures will burn easier (to a certain extent), but it's obviously not in the best interest of the manufacture to dump excess fuel into the engine just to make sure the mixture is easily ignited. These trucks definitely run lean at cruising speeds. We would have terrible gas mileage if they did not. There are two modes of operation "closed-loop" and "open-loop". In closed loop operation the car is taking feedback from the O2 sensors and targeting a stoichiometric AFR of 14.7. In open-loop operation, the O2 sensors are ignored and the fuel is delivered based on preset maps in the ecu. While cruising at low throttle and low RPMs the ecu is in closed loop and it is mapped to run very lean- I think somewhere in the 16s. This will save fuel, but you need a very good spark to ignite such a mixture. This is why misfires happen in these areas when ignition components are not in tip-top shape.


Low fuel pressure would cause issues. If you were checking fuel pressure at idle that was probably about right. A fuel pressure regulator will usually increase and reduce fuel pressure 1:1. This means it will be less at idle when there is a large vacuum. 25 psi sounds fine if base pressure is supposed to be 40 psi.

This more than likely is an ignition problem. Most of the time these type of misfires will not trigger a CEL. The hard/inexpensive way to do this would be to buy 1 coil and swap it for each of the old ones until the problem is solved. The easy/expensive way is to swap all new coils in. You should change your spark plugs if they have a lot of miles on them. Do not buy cheap chinese coils. You will have this problem again if you do.

Sorry for bumping a kind of old thread. The bad info posted here was just kind of bothering me.

 

Good info.
Thanks.

 

Sure good stuff here.

Sounds like the exact problem I've been having on my 1994 extended van with 5.8L and auto/overdrive. Happens at low torque, low rpm, at what seems to be near the bottom of the the range for the gear it just shifted into; around speeds of 30 to 35, 40 to 45, 50 to 55. Getting worse and appearing over 55 now. Feels like the whole engine wants to shut down for 1/4 second, then picks back up. But I don't have multiple coils. I read that a throttle position sensor might result in wacky mixtures at low rpms/closed throttle.

Been trying to figure out what could result with those symptoms: low torque (very slight load is when it really shows up), low rpms, pretty much goes away when you step on it, but it does miss and ping (I think it's pinging). Vacuum related ignition issue? Vacuum related fuel feed issue? Funky injectors that don't like working at low rpms and vacuum? Vacuum just a coincidental thing? Sure has me stumped. And after doing a complete tuneup.

Took it to a dealer, who did an $800 tune-up and injector service, still doing the same thing. The dealer did not check the fuel pressure, but the mechanics at two dealers said the 'bucking' (good way to describe it) didn't sound like a fuel pressure problem.

The talk of coils here make me want to replace my coil (note, not plural).

 

I found out what was causing mine it is the ac kicking off and on now that its been a little cooler were im from its stopped cause im not usin the ac

 

Sometimes this is a good way to diagnose a weak coil. The a/c will put additional load on the engine and sometimes it is enough to make the weak coil misfire at idle. This makes swapping one coil at a time to solve the problem a little easier because you can just swap in one coil, start up the truck, turn on the a/c, and wait to see if it misfires. Then repeat until problem solved. This is extra fun if it turns out to be the 8th coil you chose....

 

gap this then

 

The spark plug shown in the photo is not the one used in 97 to 03 engines.

Let me remind all that instead of doing the Checkers game of moving coils and injectors;
the use of a Scanner to look a the misfire counts for all cylinders will ID the one or ones that are causing the misfires if there is any due to a non hard fault.
This is the preferred diagnostic because you don't know if you have more than one faulty coil and maybe moving one faulty coil around or even a faulty new coil.
Doing the checkers moves often results in a decision that it is not a coil when it actually is until you catch on to it after some time, spending for other parts and frustration setting in.
Scanner diagnostic will short cut all this .
Good luck.