I have a beloved 1999 trooper I have owned since new. has 113k on and was doing the coils and ran into a problem. Aluminum bolts into an aluminum head. Bolts snapping at base, only did 1 coil and stopped. Is there any way to help avoid this? Thanks for any help.

 

The coil bolts must be steel, mine are on the 96. Odd, but someone ruined the aluminum threads in the cover? stripped them all by overtightening some time ago? Cross threaded? They have to come off to change the plugs.
You may have to drill out the bolts and put in new thread into the cover.

Or are they rusted stuck? If rusted, you can try PB Blaster, and also hammer on top of the bolt heads.

I dont know but maybe you drill all the way thru, and put a bolt on the inside so then you will have studs on the outside and use nuts to hold on the coils. But only do that if there is enough room on the inside so a bolt head wont hit anything. Other than that, JB weld some metal studs into the damaged bolt holes.