Q: My newish (3 months) MacBook Pro 15" has excessive fan noise which is getting worse, more frequent. Is there anything I can do?

Start by asking yourself what applications do you have running all the time?  Do you have anything like a cleaning program or anti-virus program running in the background?  Those use a LOT of resources that will cause the fan to run excessively.

You can also get the free program etrecheck,http://www.etresoft.com/etrecheck and run that to see what is using resources.

You can also just go to Applications, Utilities, Activity Monitor and see what the Memory Pressure is (use the Memory tab) and what the CPU load is.

If all of those results are at a low level, nothing is running and using resources, take the MacBook to an Apple store genius bar and have the techs run their diagnostics to see if there is a reason for the high fan activity.

Reset the SMC and the NVRAM:

https://support.apple.com/en-us/HT201295

https://support.apple.com/en-us/HT204063

If no success, open Activity Monitor to ALL PROCESSES and see if there are any applications using a lot of CPU resources>

https://support.apple.com/en-us/HT203184

Ciao.

Yikes! That would definitely cause the slowness and excessive fan speed. While in Activity Monitor, select the HP process and then select "Quit Process". Restart computer and check for improved performance.

HP can't write software, yours is a not uncommon problem best solved by getting rid of the HP printer and accompanying junk. Failing that at least get on to HP for software that works.

775% means that HP's printer software is using 97% of your Macs cpu, all the time.

Buy a printer that has nothing to do with HP, especially if it is cheap.

Search the site, you are not the only one with this problem.

Start in Safe Mode, then it won't run.

Do you not know about Force Quit, Safe Mode etc?

Restart your Mac while holding the shift key down, that will get Safe Mode. It will take longer to start, thats normal, be patient.

Yes, as I said before you need to remove the printer software, if you don't know how you should ask HP, they wrote it.

I'm not certain this can be accomplished at this stage, but definitely worth a try:

OS X Yosemite: Reset the printing system