Hey guys I'm fairly new to this site. Seems like some knowledgable people here. Hope you can help me. My 5.4 started running on 7 cyl. last week about a mile after I put in some gas. Just a straight constant miss , like a coil is totally dead. Eventually the engine light came on. So far I changed the fuel filter, put in dry gas, Fuel injector cleaner all this assuming it was related to the gas I put in. Next after reading a few treads in here I went with new plugs as a long shot. ( seeing the truck only has 71k) Plugs looked good but one cyl. is still out. I do alot of small engine work on 2 stroke engines. Wouldn't the spark plug be wet if the coil was bad and not burning the fuel????? All of the primary ohms of the coils seemed about the same. All of the injectors are pulsing (using this weird testor a friend loaned me) WHAT AM I MISSING? Should I buy a new coil cap and move it cyl. to cyl? or bite the bullet and bring it to the dealer? Thanks in advance -the dude

 

You stated that the CEL is on. Take the truck to the nearest Autozone and get the code read for free. Then, if the solution is not obvious, post the code on this site to get some help.

 

Not necessarily. A coil can be weak enough to cause a miss, but still have enough ***** left to fire the hole often enough to keep the plug dry. Definitely get the code read. Autozone will do it for free, so will a host of other auto-stores.

If that leads you nowhere, you can try disconnecting the plugs one at a time. When you get to the dead hole, you will not notice any difference in performance with it unplugged. But, if you unplug one of the remaining 7, being down to 6, it will run much worse.

When you get to the one that's having problems, just lay the connected plug on a ground, start it, and see if it's sparking. If it's not sparking at all, there's your problem. It could also be a dead injector, but that's less likely so it's a road to cross when you come to it. Be careful not to let it ground through you! These modern ignition systems will bite your a$$, HARD! When you get it all back together, use a ton of dielectric grease on everything that has to do with those plugs. Goop it all over those boots, really, try to use as much as possible without using so much the plug no longer makes contact.

One of the best, handiest, most coveted purchases I have EVER made was an automotive stethoscope. It's just like what a doctor uses to check you heart beat, lungs, etc. except it has a long probe on the end that you touch to what you want to listen to. They are simply amazing at what they do. If you have ever seen an old mechanic put a loooong screwdriver on an engine and put his ear to it, it's the same basic thing, just 1000x better. A definite "must have" in any wrencher's tool box. They can tell such things as whether a knock is on the top end or bottom end (sometimes even which cylinder), where they squeak is coming from, alternator, PSP, idler, etc., IF YOUR INJECTORS ARE WORKING PROPERLY, plus you can actually hear the exhaust dumping into the manifold from each cylinder (makes it super easy to detect dead holes), and gawd, a thousand other things. They are literally about the best 10-15 bucks you will ever spend. Plus just playing with it is a blast. Listening to each little part of your motor while it's running is so cool. You can hear the chains, the valves popping open and closed, the bottom end spinning around, this really neat whine from your alternator, the buzz of the impeller on your PSP, the whistle of the vacuum, being used by your accessories, and a lot more! You can tell sooooooooooooooooooo much about the health of an engine and its parts by just the sound they make.

Just be careful you don't carelessly smack the probe on something, you will be in for the loudest bang you have ever heard. You will actually feel your eardrums move in and out! OUCH!

It's situations like this that make me LOVE headers! With headers, all you need is to drive around the block a couple times, park it and leave it idling, grab a spray bottle with some plain-old water in it, and spray it on each primary. The live holes will boil the water off instantly (POOF!) the dead hole won't. It might boil it off, but it will take decidedly longer to do so, or you might just make it wet. In any case, it makes finding dead holes super easy!

 

I had a similiar problem with my 02' running a little rough it ended up being a bad injector.

 

I have a '99 as well w/a 5.4 and almost 140,000 miles. absolutely no problems EVER! Just two tail light bulbs is all I ever fixed besides normal routine maintenance. However today on the way home I gave it a little gas to get around someone and it kicked down into passing gear, and ever since it runs as if on 6 cylinders will barely stay running at idle when cold. Gonna pull all the plugs in the A.M. (well maybe after Turkey, in the afternoon) and see what I can find. Anyone had a problem like this? I am sick to my stomach that this truck isnt running right after so many miles and unsurpassed dependability. It's like someone kidnapped my wife. Got the stethoscope gonna give it a whirl tomorrow listening for the injector clicks as well as looking at the plugs.

 

Hi!

greenjd - Make sure your check engine light is working, it will light when you turn the key. Once confirmed , if not illuminated or blinking, try to force your system to produce problem. You need your check engine light to stay lit or it has to blink during a drive-cycle.
If your vehicle is running foul and still do not have light illumination, you have to push your truck hard. If it's missing or running terribly give it gas - allot of gas , keep pushing it until your system recognizes insufficient parameters.
Only once this has been accomplished you can go to Auto Zone or the dealership to get fault codes from your on-board computer. If this still fails to produce which is doubtful, then your dealership needs to probe for the problem if you have failed to determine it's origin.

You may look around for the obvious, like maybe a vac line blew off the throttle body during heavy acceleration. Look back towards the firewall on the passenger side of the motor where your heater core lines run close to your coil - look for evidence of water leakage on top of your coil.

Good Luck.

 

The weird tool my friend loaned me was a probe that when it is touched to something that vibrates makes a beep and flash with each pulse. It is called an efi tester??? It was evenly flashing as I touched each injector, If the injector is pulsing does that definetly mean fuel is coming out of the injector? or could it be plugged? Well tomorrow I will take it somewhere to get the code read and take it from there. I live in the boonies, nearest Auto Zone is about 40 miles. Does Advance Auto do that? Well as they say I'll be back. Happy Thanksgiving!

 

Noid Light - me thinks? lol


Happy Turkey day ( :

 

Jbrew, thanx for the help, pulled the plugs, #2 was damaged, #5 was wet and smeeled like gas. Compression checked #2 NO GOOD, replaced #5 OCP. Motor has a small tap and with a stethoscope you can hear it is on the 1-4 side, mainly the #2 cylinder. I think I dropped a valve or floated one, just trying to figure out if it is cheaper to buy a re-man long block or remove/re-build this one. Tomorrow I think I am gonna remove the valve cover just to see what is wrong with the valve. Hopefully the piston doesnt have a hole in it. Anyone re-built or swapped one of these lately?