I posted this in the engine/drivetrain forum, but I thought it may get more eyes over here.


Have a 2000 5.4L with 123K on it. Got ready to leave this morning for work, and truck was shuddering as I was backing out of my driveway. I stopped and put it in neutral, shudder still there, but more intense when it is in gear. Went through the 4x4 selector to make sure it hadn't somehow gotten put in 4 mode and stuck there. Usually on cold mornings I let it warm up for a few minutes, but today was about 55 degrees, so I just hopped in and started to go. I have had this truck for 3 months and driven it pretty much everyday. I have had no issue with this truck until this morning I will say that yesterday morning I had to get gas on the way to work, at a station I never get gas at. Low fuel light was on for about 6 miles. Could it be something as simple as bad gas, or condensation in the tank, even though the truck ran smooth as silk all the way to work and home again last night? It was fine when I shut it off last night, and now out of nowhere, its doing this. This isn't just a little vibration either, I mean this feels like I'm driving down a gravel road, when I'm in neutral at a stand still. As of right now, check engine light is not on. I just didn't have time to do anything with it this morning, I just hopped in my car and went to work, so I need some advise on what to look at tomorrow.

 

Sounds like it might be a bad coil. I've had to replace many on my 99 5.4 with similiar symptoms but it could be something else. It does'nt matter that it was running like a dream the day before. Try plugging in a scan tool if you have one and see if there is a code however sometimes the coil is bad with no code.

 

Yeah I had a bad coil and a code didn't appear for a few days and then it would randomly disappear. I have also seen people disconnect check engine lights to pass inspection, so you may have a code but the light doesn't work to show it.

 

Thanks, guys. Anyone know of a write up for testing the coils for a bad one? Looks like a pretty simple replacement procedure.I don't have a scanner and I am a little concerned about driving it to a store to use theirs. I'm still wondering if I may have gotten some bad gas. How in the heck would I figure out if its the gas or not? I put 10 gallons in there yesterday. That's a lot to drain out. Would an additive be able to rectify a water or contaminant problem?

 

It does sound like a bad coil. I know you said you don't want to take it to scan it,but take it to a autoparts store to scan it. Most of the major chains will scan it for free. Even if you check engine light isn't on, you may have a pending code stored in the computer. I had the same problem with mine 3 years ago after I bought my 99 5.4. I just went ahead and changed all 8 coil packs and changed all my plugs at once. My thought was if one is going bad, the rest of the coils are bound to fail in the near future. If you think you may have some bad fuel or water in the tank. STP makes a number of products for water in the tank or even a octane booster. Good luck.

 

By all means use their free scan. If theirs does'nt produce a code then neither is the one you might buy.( which I would still reccomend) Unfortunately there is no other way besides taking it to a mechanic to run a more detailed diagnostic. You could just buy one new one and do the old swap one at a time deal buy that can be a pain or you may be able to unplug one at a time with the truck running and see if the idle stays bad or does'nt get worse however the back ones are a little harder to get to but can be done. I just changed my plugs, coils and injectors and still had a bad new one that I could'nt figure out. Its not hard if you've never done it. Just get a stepladder and lean in and start with the easy ones first. Pinch the bottom side of the electrical connector and wiggle a little and pull straight back and see what happens with the idle. You may get lucky. If you have to replace one than get some extensions and I think a 7 mm socket and take out the set screw holding it in on the side of the coil.( dont drop the screw) unplug the connector and pull upward. It may seperate from the rubber boot but don't panic, pull the boot out with needle nose pliers or something. Put a little dielectric grease on the new one bottom side and put it back in, line up the set screw hole, install the screw, tighten it down(dont go crazy) and plug the connector back in. Im pretty sure I was able to weasle my hand in to the back ones too without removing the fuel rails at least on the passenger side anyway. If you dont think you can handle it I think I paid around $150.00 for the mechanic to diagnose and install one new one. Yep, that is why I learned to do them myself. By the way, I really doubt its the gas you bought but Im not a mechanic so dont quote me. Good luck and let us know how it goes.

 

Thanks for all of the suggestions and encouragement, guys. Brought a volt/ohm meter home from work yesterday to test the coils. Hoping to get to it today between preparations for my son's b-day party tomorrow. Will update as soon as I find out what's going on here.

 

Did you ever test the coils with a multimeter? My '99 5.4L has always had a very mild kick at idle and I know its not a lumpy cam.

 

I never tested my coils. I"ve only replaced them when they through a code. I can tell you this, after I replaced my plugs, coils and injectors ( ebay refurbished) My truck starts right up and has no jumps in the idle or anything but still has what I"ll call a tick tick tick which it has had for many yrs. Not quite a deisel sound but noticible. It has 190,000 and still running good. Im more concerned about the rust I see when Im under it............Yikes. I could'nt tell you what fixed my slow start, plugs, injectors or coils, ( Im not that good) but I"d bet my injectors