I noticed the other day my 99 5.4 started to skip and vibrate pretty bad when idling and driving, so I took it to a carquest when the Service Engine light came on to get a code reading. The reading indicated that my upstream bank 1 O2 sensor was bad. I bought the part, changed it out (which was a pain,) and reset the code. Still having the same problem. The light hasn't come back on yet. I'm thinking it is a coil because it feels like a cylinder misifiring, but from everything I've seen, readers usually indicate that a cylinder is misfiring. Any suggestions before I take it to a shop?

 

How many miles are on the plugs and coils? Sounds like a low grade misfire. Pretty much its not a hard miss where the PCM can pickup the coil output. If it pver 100k miles it time for plugs at a minimum. I would replace the coils also. But that is just me.

 

140K miles on the truck. I've owned it about two years, and I don't know if the coils or plugs have ever been changed.

 

With the truck running unplug one coil at a time. If the shake gets worse plug it back in and move the the next. If you get to one that doesn't make it worse that's your bad coil.

Wayne

 

Or use a scanner to find which cylinder is misfiring.

 

Will a scanner pick it up if the light isn't on?

 

Only a scanner that can read mode 6 misfire data.

 

Most hand held turners that are able to pull codes will only pull misfire codes if there is a light. It does pull some codes that don't trigger a light but misfire codes is not one of them.

I have seen coils go bad and NEVER throw a code. Like I said above just unplug the coils one at a time and if you unplug one and the shake doesn't change that's your bad coil!

Wayne

 

when my coil went bad from a bit too much fun at a mud hole I used some snap on touch screen scanner that picked my misfire up and what cylinder. But the ones at auto part stores would not.

 

Wayne has the easiest and cheapest way of determining a bad coil.

Chances are the plugs are original I would pull a few plugs check the condition anyway since you've Owned it for two years now. I would grab a set of plugs and coils and slap them in a couple hundred dollars and depending on how familiar you are on changing these plugs maybe an hour or could be an afternoon of work.

Edit: just so you are aware "pocket scan tools" are usually anywhere between $30-$100 they can only read the trouble code and delete it (some only read it) a step up would be $100-$400 this would have the capability of doing ABS and SRS code readout as well as readiness codes which is what the emissions test looks at whether or not the vehicle completed a drive cycle and all systems are functioning normally and then $400+ you get the capability of more advanced diagnostics where you can check live data and operate different systems components by the touch of a button.

Also I will add there are scan tools that do different functions and are all over the place in price ranges

Mac tools actually sells a scan tool that keeps up with snap on modis for a fraction of the price I believe it's like $350 and not more than $500. Snap ons scan tools are outrageous in price I purchased mine for $2500 about 8 years ago