Alright guys I could really use your insight, I have a 97 f150 with 4.6 and i had some problems today. It ran great this morning and then when it got to be about 80 degrees outside the truck started lacking a lot of power going up hills and when I was on the highway I had to downshift to get up to speed and it does 65mph barely on throttle easy any other day. Also It seemed like power got worse when I turned on the AC that was one thing I noticed. Also I installed a K&N CAI over the winter and with cool air yea probably works awesome but the first day its hot its starts lacking power and I'm thinking that may be because its sucking air in from the engine bay which is hot too. Truck also has 176k so if you guys think some things should be replaced give me some input I'm putting my stock intake on tomorrow so hopefully that will help. Theres no codes and I'm lost on this one any help is appreciated thx-Zach

 

How old is the tune up.. and fuel filter.... AC sucks power also... Is the K&N clean and oil'd?

 

The Air Filter is pretty clean and the fuel filter was changed in september of 2010, and plugs and wires around the same time. And yes I know the engine works harder with the ac but its never been a problem before or at least to the point where I would notice it. Also what consists of a tuneup I have replaced quite a few things but what exactly should be replaced.

 

If there are no codes, and the engine runs good, then it just sounds like an old motor. Maybe it is low on compression. That would reduce the power significantly. You can do a quick compression test to see how healthy the engine is.

 

BTW the 4.6L should have at least 150 psi across the board.... a ten percent variation would indicate a weak cylinder

 

Put the stock intake back on if you have it, reset the ECU, and see how it feels. It's rare but not out of the question an aftermarket intake could cause issues on a 2V motor.

A full tune up in my book includes the following:

Plugs, wires/COPs, throttle body cleaning (this includes the EGR and IAC ports), MAF cleaning, front O2 sensors, fuel filter, PEA based fuel system cleaner, air filter, transmission fluid and filter, differential fluid, lubrication of the front end and driveshaft, repack wheel bearings, inspection for vacuum and exhaust leaks, PCV valve, coolant flush, new brake fluid, and power steering fluid.

I'm sure I'm forgetting something in that list, but it's a good start.

 

None of that will do any good if the compression is bad

 

Its 14 years old I know its an old motor but it ran great till yesterday.

 

Just answering his question of what a full tune up consisted of

 

Like I said before, do a simple compression test. If the numbers are low, you know why she doesn't pull like she used to. If compression is good, then you know the problem lies somewhere else....