Ron,

When you serviced your plugs did you remove the fuel rail? If you did pull it off again and inspect the rubber O rings, the fuel return lines for kinking and each injector for any visible signs of damage and all the electrical connectors for bent pins or corrosion. If you have access to a fuel pressure guage check the pressure at the shrader valve.

JMC

 

I'll throw out a really wild off the wall suggestion.

I don't even know if our trucks have them or not and I'm not even sure it would manifest itself with the symptoms you describe.

Could the crankshaft pulley have slipped on the rubber damper? Again, not even sure we have a rubber damper or not, but couldn't that change the timing (relation to the sensor) and setup a vibration?

 

I would think that if I had a bad O2 sensor the thing would throw a code. I did think about that but it's one of those things where if no code, no problem.... Maybe that train of thought is wrong. I don't know.

JMC, no I did not take off the fuel rail when I changed my plugs but I probably should check the fuel pressure. I don't have a gauge though so I'll have to either buy one or borrow one. The fuel pump is about the only thing I have not looked at. Still no check engine light either. Weird.

I do not believe that there is a sensor associated with the crank pulley. When I swapped out the pulley when I installed my Powerdyne SC (which is currently disabled to troubleshoot this probles) I did not see any magnet or anything that would trigger a sensor. The pully on there right now is not the stock pulley. It has a hub that's machined flat to mount the SC pulley. It's just like stock, it's just been slightly modified. The problem first came up about 10k miles after I installed the SC. Since the problem has been there the SC has been disabled, I removed the SC belt.

Another possibility was the fuel regulator that came with the SC. I temporarily removed that as well to eliminate as many things as possible.

Still working on it. Hopefully something will come to light soon. I am going to check fuel pressure though. If that's OK I may just replace the O2 sensors for the heck of it. I don't think they are very expensive these days.

Thanks for all the feedback and ideas...

 

My 99 5.4 expy started the same thing yesterday. Driving me nuts. It's bad enough that it's not drivable. No power whatsoever. It doesn't stall, but you think it's going to when you press the gas. Just shakes like crazy and creeps down the driveway. I've no clue about this, and it's not throwing a code yet.

Looking forward to one of us figuring this out to maybe help the other guy.

 

OK, found problem and fixed it. Or so it would seem.

I had at least 1 bad spark plug. I decided to replace them again with the original Motorcraft plugs and the engine runs great. No missing or poor idle. I don't know if there were cracked insulator(s) or what but I figured I just do it for the heck of it since it's a cheap thing. Knuckle skinner, but cheap.

Now I just need to put the Powerdyne drive belt back on and I'm back in business.

Thanks to all who provided suggestions...

Ron

 

Fixed mine too. Turned out to be a slow drip on the passenger rear coilpack from the heater hose. Evidently a common problem. This wasn't the original coilpack. It evidently happened before (I got the truck used) and the first repair didn't fix the hose properly. To all those interested, measuring the resistance of the coils per the Haynes manual doesn't always tell you anything. My coilpack read just fine, but it was bad. If it reads bad, it's bad, if it reads okay then it's still questionable.