My canon imageclass mf4270 jams 90% of the time when i try to print. sometimes if i pull out the toner cart several times. it will print.

From your program select File - Print. In the window that opens up there should be a button marked Preferences or Properties. Select that to see the available options for your printer. There should be an option to select Black and White. They may call it monochrome too. Select that and it will print only using black ink.

you can Adjust the density level of scanned image manually from MF4270 read the manual
if you don't have manual please visit this link
Download Canon imageCLASS MF4270 Reference Manual

hope that it will solve your problem

That is best bet since it appears that your print head is fubar and Canon charges a fortune for them. Cheaper to get a new printer with warranty.

If you removed and reinstalled toner correctly several times and this error code is flashing, you need to try another new toner cartridge, even though the other one may seem still good to you. If this doesn't remedy problem the Troubleshooting section of the Canonusa.com website says to call 1-800-OK-CANON.

Sometimes the simplest solution is the best solution. On pretty much all small Canon copiers, the issue of 1/2 blank copies or blank area down the page is the toner cartridge. Just remove the cartridge and shake it from side to side to level out the toner then re-install. This will fix the problem at least 90% of the time.
Thank You for using Fixya.

First make sure that the USB cable is OK and use another if you have one. Then make sure that the laptops have working USB ports from Device Manager. If they are OK then try powering up the Canon again without the USB cable connected to see if any errors are reported and then plug it in to your laptop to see if it is recognised. Check the status of the Canon Print Driver settings. If this all fails then you may have defective USB ports on the Canon and will need to get them repaired.

turn off and unplug for a good 10 seconds, then plug in/power on. If it still shows jam, have another look inside, some torn paper might be jammed inside.

try this

1. Turn off the printer.
2. Remove any paper trays. Inspect them for wrinkled or damaged paper.
3. Also open the back cover of the printer if this model has one.
4. Open any other doors that give access to the printer's paper path and to the toner or ink cartridge.
5. If necessary, remove the toner or ink cartridge. Place it away from light/ sun light to avoid damaging it.
6. If you find a piece of jammed paper, remove it by holding it with both hands and pulling firmly. The goal is to keep the paper from tearing. If several pieces are jammed together, try pulling out the middle piece first to loosen the jam.
7. If the paper does tear, try rotating the roller gears manually to free the paper. Don't force anything, though. Do this step especially if the jam message comes up repeatedly without any obvious paper jam, there may be a small tear of paper inside.
8. Ones the printer is free of paper Replace the toner or ink cartridge and paper trays, close any doors you opened and turn the printer back on.
9. If the printer paper jam message still appears, then there is still some paper in the printer. Reinspect the paper path.
10. see alternative if the problem is still not solved.
    

alternative :
Load a piece of thick paper, for example photo paper and press the resume button (may be diffrent button on diffrent models) a few times to the printer picks up the paper and puts it through the machine.

try downloading here - http://www.usa.canon.com/consumer/controller?act=ModelInfoAct&tabact=DownloadDetailTabAct&fcategoryid=335&modelid=15753 - also choose the right operation system on top

Have you checked the obvious things? Such as pulling the tape off the new cartridge? Also make sure the transfer roller under the toner cart. is in securely.