Hope you guys can help with my delima..... I have an engine miss or stumble at around 55 to 60 mph. It seems to be more pronounced as I come to hill or overpass. The truck has 93000 miles on the engine. I have replaced the plugs, fuel filter. There is no "Check engine" light on at this time. Hopefully someone can point me in the right direction...

Thanks for the anticipated help.

Pods

 

This reminds me of a fuel related problem a friend had with an El Camino in the mid seventies. Halloweeners had put golf ***** in his fuel tank, which would suck up against the pick-up screen at odd times.

Another friend had a similar problem with a class 7 vehicle diesel with a Cat 3208. The way he found the problem: he was working on the truck with the saddle tank fuel cap off, when he seen the styrofoam cup floated past the tank opening. Removal of the cup cured the problem.

 

Does it feel like a dead miss?5.4L? Im goin to guess a COP(coil on plug 1 per cylinder) is goin bad.....I just had the same happen to mine this week. Ran diagnostic check(I had no check engine light on either) and revealed that the #4 cylinder was my culprit. You could have one of the eight goin bad.If you dont have a diagnostic tool run it by autozone or advance to pull the codes for free. I bet you will find the problem...... Just something to think about BTW, my truck is a 99 Lariat 4x4 Flareside 5.4. To be honest with you it has been a POS!

 

99Flare, unless there is a CEL, neither Advance nor Autozone can help. Their code readers are just that, code readers. A full diagnostic scan tool, such as AutoTap, can show misfires real-time.
Pods, the way a PCM senses misfires is actually kind of neat. The crank position sensor senses crankshaft speed and acceleration. Since the PCM knows when each cylinder should be firing, if the crank sensor does see the acceleration for that instant, it's a misfire. There's a threshhold of minumum misfires (I don't know the nummber offhand) that must happen in order to light the CEL. Just b/c the CEL is not lit, do not rule out a simple misfire. Have someone help you and put an extra plug in each boot one at a time and see if it's firing. Unplug all boots so that the engine does not crank off with your hand in there. There's also a tool at Autozone for this called a spark plug tester. Not easy, but beats spending $XXX. Barring that, you could do resistance checks on the coils, but if it's not enough to trip the CEL, then they'll all probably check out ok.

Sorry if I made this too basic, but I don't know what you know about cars. Hope this helps.

 

a few other things to check;

#4 coil very common to have coolant leak on it with the 99's
dirty maf
loose coil wire
loose injector wire
the wire harness up against the ac accumulator
dirty buuterfly valve (do not use carb cleaner)
going bad injector
dirty battery terminal/s
going bad o2 sensor
etc...

 

Hmmm...I figured they could read it. I know my Innova 3110 picked it up without a check engine light being on. Im guessing theere equiptment is rather basic? It was just a suggestion......

 

No, they have the $39.99 reader that's on their shelf. The only thing it is good for is reading CEL codes. I apologize if I sounded rude, that certainly was not my intention. It was a good suggestion, just not one which would work. Keep posting regardless. I'm wrong all the time, but I keep posting anyway. It's how you learn, and that's what this board is all about.

 

It was never taken as rude.......no kidding! Back to the origional ?...did you get anything done to the truck?

 

I was thinking something electrical, fuel might be it too. Did this happen after you replaced the plugs and/or fuel filter, or did you just replace those to see if it fixed the problem?

If its a 4.6, might be the plug wire, I had the same problem, if its a 5.4, COP's possibly as mentioned, or fuel problems (injectors possibly).

You can check the wires and COP's with a DMM, and you can you can use a screw driver to check the injectors (stick the metal part on top of the injector, and hold the handle to your ear, you should hear a rapid clicking noise).

Those are the things I would check out first anyway.