I have a 98' w/ 5.4 V8, just hit 100k. I am having this annoying problem on acceleration. Say your getting on the interstate accelerating from 45 to about 65, engine starts shuddering similar to running a lower octane gas. Stomp on the gas and it clears up and accelerates normally. Sometimes I get the check engine light that eventually goes out. I usually get the problem in the 45 to 70 mph range. Never had this problem until recently.

I have searched the threads and I am at a loss for a starting point. I am due for a plug change but this feels like a sensor problem. Thanks in advance.

 

I have a '98 4x4 with the 5.4. I had the same problem a while back. It was just like I had put some WAY CHEAP gas in my truck.

I undertook the painstaking task of new plugs. Although the truck needed them, it didn't help my problem.

I started searching the forum for a solution. I found two good ones. I tried two things at the same time. I wish now that I had done them one at a time to see exactly which one worked.

I read on one of the engine forums about pulling the main harness away from the a/c evaporator. I know it sounds funny but check out this link to the thread. https://www.f150online.com/forums/sh...t=main+harness

Second, I cleaned the MAF Mass Airflow Sensor. It was NASTY! Here is a link to one of the sponsors with a detailed description on how to do it. http://www.fordf150.net/howto/clean-...low-sensor.php

Like I said, I did both of these and no more pinging or rough idle!

Good luck.

 

I am having problems with my 98 5.4 idling rough/vibrating at normal op temp. Researching DPFE problems, I found this thread that sounded like your situation. I'm afraid I don't know how to save the link as one you can just click on and go... but I hope it is still helpful.


https://www.f150online.com/forums/sh...highlight=DPFE

 

Cool, guess I can do it!

 

Just bought a can of Seafoam. The stuff seems to work. I just added bottle to my last tank of gas. Going to do the other recommeded cleaning of the PCV system next.