Hello,

I have a 1999 F150 with a V8 4.6L engine. I have been experiencing some engine shutter and slight lose of power when going up hills, usually at highway speed. If I keep the rpms steady or slightly increasing I do not noticed it as bad, however if I have to slow down and then accelerate again it really starts to shutter badly. I replaced the spark plugs awhile back and it seemed to fix the problem for a few weeks, but it slowly got worse and now it is as bad as it was before the replacement. Any ideas? Thanks in advance for any suggestions!

 

I would say one of your coils are getting week I have a week one to but my computer hasn't picked it up yet it does it up hills at highway speeds also

 

Most likely coils. You might want to run a compression check since bad valves can also cause engine misses like you are describing. If it's coils, I'd recoomend replacing them all. Use Motorcraft if you can afford them, but the cheapos on eBay will do if you can't.

 

Also has your check engine light came on ?

 

Thanks for the info guys! I will try to get over to autozone this weekend and see if they can pull any codes. The check engine light did come on way back before I replaced the SP but I have not seen it come back on since then. Hopefully they can still pull at least that old code to maybe give me a clue. Thanks again.

 

Sounds like your fuel filter is plugged or your fuel pump is failing.

 

I have the same deal going on with my truck. I am going to change my coil packs this week and hopefully that will fix it if i run across anything i will post hope you got yours running right