Hey, new to the forum. Got a 98 F150 4x4 4.6 with 201,000 miles. Recently started running rough. I replaced spark plugs with Motorcraft, cleaned throttle body, cleaned air filter, and cleaned MAF sensor. Does not read a check engine code, Need some suggestions, please. Thanks

 

Plug wires? Coil packs?

Throw a bottle of Techron in the gas. Replace the fuel filter.

 

Was it running rough before or after you changed the sparkplugs? The plugs have to be torqued right or they will loosen and come out causing drivability issues obviously.

 

Yeah, I am sorry to have left out important details. Truck started running rough, as in sitting there idling or driving at slow or fast speeds with absolutly zero power and shuddering. I replaced the fuel filter and cleaned throttle body 8,000 miles ago. Since it started running rough, I have only changed the spark plugs and cleaned the MAF sensor and still no improvement. Hope I did not leave anything out.
Thanks

 

How many miles on those plug wires? That's what I'd look at next. My first wire set lasted 90k miles, the second only 70k. I also have a '98 4.6 with 202,000 on it and have experienced the shudder you're describing many times. Every time it has been misfire related. I used to use Autolite plugs, but forever changed my tune after the 4th one went bad in the same set. Also, I'd check to see if your intake gaskets are leaking coolant down into the plug well. This happened to me recently and that was probably the most violent, consistent shuddering.

 

Hey, cool hand
Yeah, the wires have 10,000 miles on them. When you were talking about the coolant issue, how exactly would I check that. The coolant level in the recovery tank never moves. It's good to know that you have a truck with the same miles. I love the truck, just want to resolve the issue.
Thanks

 

My coolant level dropped very slowly because the intake gasket was only seeping. I had no easily visible external indication of a leak. I had read about the leaking intake gasket problem here on the board so I knew that it was USUALLY limited to the plug wells closest to the coolant "crossover" (or whatever you call it) in the intake. That narrowed it down to #1, 4, 5, and 8 (or the very front and very back on both banks). I got lucky though in that my truck finally threw a "check engine" light and I found that my misfire was #5. To check for coolant, I just pulled the wire and put a rolled up paper towel down in the plug well for a couple of seconds. It came back up wet and green. From there, I figured that the only source of coolant in #5 could be the intake gasket. So, I drained the coolant, pulled the intake and changed them out. It took me about 5 hours, but I'm sure it could be done faster.

I don't know if that's your problem, but it worked for me. Good luck!

 

Ever changed ur IAC? Ive heard EGRs causing this issue as well. I have a 97 w/ 145K and have had to change both...unfortunately I just noticed a coolant leak at cylinder 1 as well (cracked gasket) GL

 

ya like parnaz said id clean your iac and maybe replace your egr valve and check metal hose that runs to it on mine it was nearly clogged shut also check your vaccum system for leaks like your pcv valve and the hose that goes to the back of the throttle body for cracks.

 

My truck was having this issue, literally the day before I left on deployment. I didn't have the time to fix it obviously, so my buddy told me he'd take care of it. It turned out to be a vacuum leak. Not sure from which line, but he replaced the line and it fixed it. Try checking that out.